JDK8/Java8源码在线阅读
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* accompanied this code).
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package javax.swing;
import java.awt.*;
import java.awt.event.*;
import java.awt.datatransfer.*;
import java.awt.dnd.*;
import java.beans.*;
import java.lang.reflect.*;
import java.io.*;
import java.util.TooManyListenersException;
import javax.swing.plaf.UIResource;
import javax.swing.event.*;
import javax.swing.text.JTextComponent;
import sun.reflect.misc.MethodUtil;
import sun.swing.SwingUtilities2;
import sun.awt.AppContext;
import sun.swing.*;
import sun.awt.SunToolkit;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.security.AccessControlContext;
import java.security.ProtectionDomain;
import sun.misc.SharedSecrets;
import sun.misc.JavaSecurityAccess;
import sun.awt.AWTAccessor;
/**
* This class is used to handle the transfer of a <code>Transferable</code>
* to and from Swing components. The <code>Transferable</code> is used to
* represent data that is exchanged via a cut, copy, or paste
* to/from a clipboard. It is also used in drag-and-drop operations
* to represent a drag from a component, and a drop to a component.
* Swing provides functionality that automatically supports cut, copy,
* and paste keyboard bindings that use the functionality provided by
* an implementation of this class. Swing also provides functionality
* that automatically supports drag and drop that uses the functionality
* provided by an implementation of this class. The Swing developer can
* concentrate on specifying the semantics of a transfer primarily by setting
* the <code>transferHandler</code> property on a Swing component.
* <p>
* This class is implemented to provide a default behavior of transferring
* a component property simply by specifying the name of the property in
* the constructor. For example, to transfer the foreground color from
* one component to another either via the clipboard or a drag and drop operation
* a <code>TransferHandler</code> can be constructed with the string "foreground". The
* built in support will use the color returned by <code>getForeground</code> as the source
* of the transfer, and <code>setForeground</code> for the target of a transfer.
* <p>
* Please see
* <a href="https://docs.oracle.com/javase/tutorial/uiswing/dnd/index.html">
* How to Use Drag and Drop and Data Transfer</a>,
* a section in <em>The Java Tutorial</em>, for more information.
*
*
* @author Timothy Prinzing
* @author Shannon Hickey
* @since 1.4
*/
@SuppressWarnings("serial")
public class TransferHandler implements Serializable {
/**
* An <code>int</code> representing no transfer action.
*/
public static final int NONE = DnDConstants.ACTION_NONE;
/**
* An <code>int</code> representing a "copy" transfer action.
* This value is used when data is copied to a clipboard
* or copied elsewhere in a drag and drop operation.
*/
public static final int COPY = DnDConstants.ACTION_COPY;
/**
* An <code>int</code> representing a "move" transfer action.
* This value is used when data is moved to a clipboard (i.e. a cut)
* or moved elsewhere in a drag and drop operation.
*/
public static final int MOVE = DnDConstants.ACTION_MOVE;
/**
* An <code>int</code> representing a source action capability of either
* "copy" or "move".
*/
public static final int COPY_OR_MOVE = DnDConstants.ACTION_COPY_OR_MOVE;
/**
* An <code>int</code> representing a "link" transfer action.
* This value is used to specify that data should be linked in a drag
* and drop operation.
*
* @see java.awt.dnd.DnDConstants#ACTION_LINK
* @since 1.6
*/
public static final int LINK = DnDConstants.ACTION_LINK;
/**
* An interface to tag things with a {@code getTransferHandler} method.
*/
interface HasGetTransferHandler {
/** Returns the {@code TransferHandler}.
*
* @return The {@code TransferHandler} or {@code null}
*/
public TransferHandler getTransferHandler();
}
/**
* Represents a location where dropped data should be inserted.
* This is a base class that only encapsulates a point.
* Components supporting drop may provide subclasses of this
* containing more information.
* <p>
* Developers typically shouldn't create instances of, or extend, this
* class. Instead, these are something provided by the DnD
* implementation by <code>TransferSupport</code> instances and by
* components with a <code>getDropLocation()</code> method.
*
* @see javax.swing.TransferHandler.TransferSupport#getDropLocation
* @since 1.6
*/
public static class DropLocation {
private final Point dropPoint;
/**
* Constructs a drop location for the given point.
*
* @param dropPoint the drop point, representing the mouse's
* current location within the component.
* @throws IllegalArgumentException if the point
* is <code>null</code>
*/
protected DropLocation(Point dropPoint) {
if (dropPoint == null) {
throw new IllegalArgumentException("Point cannot be null");
}
this.dropPoint = new Point(dropPoint);
}
/**
* Returns the drop point, representing the mouse's
* current location within the component.
*
* @return the drop point.
*/
public final Point getDropPoint() {
return new Point(dropPoint);
}
/**
* Returns a string representation of this drop location.
* This method is intended to be used for debugging purposes,
* and the content and format of the returned string may vary
* between implementations.
*
* @return a string representation of this drop location
*/
public String toString() {
return getClass().getName() + "[dropPoint=" + dropPoint + "]";
}
};
/**
* This class encapsulates all relevant details of a clipboard
* or drag and drop transfer, and also allows for customizing
* aspects of the drag and drop experience.
* <p>
* The main purpose of this class is to provide the information
* needed by a developer to determine the suitability of a
* transfer or to import the data contained within. But it also
* doubles as a controller for customizing properties during drag
* and drop, such as whether or not to show the drop location,
* and which drop action to use.
* <p>
* Developers typically need not create instances of this
* class. Instead, they are something provided by the DnD
* implementation to certain methods in <code>TransferHandler</code>.
*
* @see #canImport(TransferHandler.TransferSupport)
* @see #importData(TransferHandler.TransferSupport)
* @since 1.6
*/
public final static class TransferSupport {
private boolean isDrop;
private Component component;
private boolean showDropLocationIsSet;
private boolean showDropLocation;
private int dropAction = -1;
/**
* The source is a {@code DropTargetDragEvent} or
* {@code DropTargetDropEvent} for drops,
* and a {@code Transferable} otherwise
*/
private Object source;
private DropLocation dropLocation;
/**
* Create a <code>TransferSupport</code> with <code>isDrop()</code>
* <code>true</code> for the given component, event, and index.
*
* @param component the target component
* @param event a <code>DropTargetEvent</code>
*/
private TransferSupport(Component component,
DropTargetEvent event) {
isDrop = true;
setDNDVariables(component, event);
}
/**
* Create a <code>TransferSupport</code> with <code>isDrop()</code>
* <code>false</code> for the given component and
* <code>Transferable</code>.
*
* @param component the target component
* @param transferable the transferable
* @throws NullPointerException if either parameter
* is <code>null</code>
*/
public TransferSupport(Component component, Transferable transferable) {
if (component == null) {
throw new NullPointerException("component is null");
}
if (transferable == null) {
throw new NullPointerException("transferable is null");
}
isDrop = false;
this.component = component;
this.source = transferable;
}
/**
* Allows for a single instance to be reused during DnD.
*
* @param component the target component
* @param event a <code>DropTargetEvent</code>
*/
private void setDNDVariables(Component component,
DropTargetEvent event) {
assert isDrop;
this.component = component;
this.source = event;
dropLocation = null;
dropAction = -1;
showDropLocationIsSet = false;
if (source == null) {
return;
}
assert source instanceof DropTargetDragEvent ||
source instanceof DropTargetDropEvent;
Point p = source instanceof DropTargetDragEvent
? ((DropTargetDragEvent)source).getLocation()
: ((DropTargetDropEvent)source).getLocation();
if (SunToolkit.isInstanceOf(component, "javax.swing.text.JTextComponent")) {
dropLocation = SwingAccessor.getJTextComponentAccessor().
dropLocationForPoint((JTextComponent)component, p);
} else if (component instanceof JComponent) {
dropLocation = ((JComponent)component).dropLocationForPoint(p);
}
/*
* The drop location may be null at this point if the component
* doesn't return custom drop locations. In this case, a point-only
* drop location will be created lazily when requested.
*/
}
/**
* Returns whether or not this <code>TransferSupport</code>
* represents a drop operation.
*
* @return <code>true</code> if this is a drop operation,
* <code>false</code> otherwise.
*/
public boolean isDrop() {
return isDrop;
}
/**
* Returns the target component of this transfer.
*
* @return the target component
*/
public Component getComponent() {
return component;
}
/**
* Checks that this is a drop and throws an
* {@code IllegalStateException} if it isn't.
*
* @throws IllegalStateException if {@code isDrop} is false.
*/
private void assureIsDrop() {
if (!isDrop) {
throw new IllegalStateException("Not a drop");
}
}
/**
* Returns the current (non-{@code null}) drop location for the component,
* when this {@code TransferSupport} represents a drop.
* <p>
* Note: For components with built-in drop support, this location
* will be a subclass of {@code DropLocation} of the same type
* returned by that component's {@code getDropLocation} method.
* <p>
* This method is only for use with drag and drop transfers.
* Calling it when {@code isDrop()} is {@code false} results
* in an {@code IllegalStateException}.
*
* @return the drop location
* @throws IllegalStateException if this is not a drop
* @see #isDrop()
*/
public DropLocation getDropLocation() {
assureIsDrop();
if (dropLocation == null) {
/*
* component didn't give us a custom drop location,
* so lazily create a point-only location
*/
Point p = source instanceof DropTargetDragEvent
? ((DropTargetDragEvent)source).getLocation()
: ((DropTargetDropEvent)source).getLocation();
dropLocation = new DropLocation(p);
}
return dropLocation;
}
/**
* Sets whether or not the drop location should be visually indicated
* for the transfer - which must represent a drop. This is applicable to
* those components that automatically
* show the drop location when appropriate during a drag and drop
* operation). By default, the drop location is shown only when the
* {@code TransferHandler} has said it can accept the import represented
* by this {@code TransferSupport}. With this method you can force the
* drop location to always be shown, or always not be shown.
* <p>
* This method is only for use with drag and drop transfers.
* Calling it when {@code isDrop()} is {@code false} results
* in an {@code IllegalStateException}.
*
* @param showDropLocation whether or not to indicate the drop location
* @throws IllegalStateException if this is not a drop
* @see #isDrop()
*/
public void setShowDropLocation(boolean showDropLocation) {
assureIsDrop();
this.showDropLocation = showDropLocation;
this.showDropLocationIsSet = true;
}
/**
* Sets the drop action for the transfer - which must represent a drop
* - to the given action,
* instead of the default user drop action. The action must be
* supported by the source's drop actions, and must be one
* of {@code COPY}, {@code MOVE} or {@code LINK}.
* <p>
* This method is only for use with drag and drop transfers.
* Calling it when {@code isDrop()} is {@code false} results
* in an {@code IllegalStateException}.
*
* @param dropAction the drop action
* @throws IllegalStateException if this is not a drop
* @throws IllegalArgumentException if an invalid action is specified
* @see #getDropAction
* @see #getUserDropAction
* @see #getSourceDropActions
* @see #isDrop()
*/
public void setDropAction(int dropAction) {
assureIsDrop();
int action = dropAction & getSourceDropActions();
if (!(action == COPY || action == MOVE || action == LINK)) {
throw new IllegalArgumentException("unsupported drop action: " + dropAction);
}
this.dropAction = dropAction;
}
/**
* Returns the action chosen for the drop, when this
* {@code TransferSupport} represents a drop.
* <p>
* Unless explicitly chosen by way of {@code setDropAction},
* this returns the user drop action provided by
* {@code getUserDropAction}.
* <p>
* You may wish to query this in {@code TransferHandler}'s
* {@code importData} method to customize processing based
* on the action.
* <p>
* This method is only for use with drag and drop transfers.
* Calling it when {@code isDrop()} is {@code false} results
* in an {@code IllegalStateException}.
*
* @return the action chosen for the drop
* @throws IllegalStateException if this is not a drop
* @see #setDropAction
* @see #getUserDropAction
* @see #isDrop()
*/
public int getDropAction() {
return dropAction == -1 ? getUserDropAction() : dropAction;
}
/**
* Returns the user drop action for the drop, when this
* {@code TransferSupport} represents a drop.
* <p>
* The user drop action is chosen for a drop as described in the
* documentation for {@link java.awt.dnd.DropTargetDragEvent} and
* {@link java.awt.dnd.DropTargetDropEvent}. A different action
* may be chosen as the drop action by way of the {@code setDropAction}
* method.
* <p>
* You may wish to query this in {@code TransferHandler}'s
* {@code canImport} method when determining the suitability of a
* drop or when deciding on a drop action to explicitly choose.
* <p>
* This method is only for use with drag and drop transfers.
* Calling it when {@code isDrop()} is {@code false} results
* in an {@code IllegalStateException}.
*
* @return the user drop action
* @throws IllegalStateException if this is not a drop
* @see #setDropAction
* @see #getDropAction
* @see #isDrop()
*/
public int getUserDropAction() {
assureIsDrop();
return (source instanceof DropTargetDragEvent)
? ((DropTargetDragEvent)source).getDropAction()
: ((DropTargetDropEvent)source).getDropAction();
}
/**
* Returns the drag source's supported drop actions, when this
* {@code TransferSupport} represents a drop.
* <p>
* The source actions represent the set of actions supported by the
* source of this transfer, and are represented as some bitwise-OR
* combination of {@code COPY}, {@code MOVE} and {@code LINK}.
* You may wish to query this in {@code TransferHandler}'s
* {@code canImport} method when determining the suitability of a drop
* or when deciding on a drop action to explicitly choose. To determine
* if a particular action is supported by the source, bitwise-AND
* the action with the source drop actions, and then compare the result
* against the original action. For example:
* <pre>
* boolean copySupported = (COPY & getSourceDropActions()) == COPY;
* </pre>
* <p>
* This method is only for use with drag and drop transfers.
* Calling it when {@code isDrop()} is {@code false} results
* in an {@code IllegalStateException}.
*
* @return the drag source's supported drop actions
* @throws IllegalStateException if this is not a drop
* @see #isDrop()
*/
public int getSourceDropActions() {
assureIsDrop();
return (source instanceof DropTargetDragEvent)
? ((DropTargetDragEvent)source).getSourceActions()
: ((DropTargetDropEvent)source).getSourceActions();
}
/**
* Returns the data flavors for this transfer.
*
* @return the data flavors for this transfer
*/
public DataFlavor[] getDataFlavors() {
if (isDrop) {
if (source instanceof DropTargetDragEvent) {
return ((DropTargetDragEvent)source).getCurrentDataFlavors();
} else {
return ((DropTargetDropEvent)source).getCurrentDataFlavors();
}
}
return ((Transferable)source).getTransferDataFlavors();
}
/**
* Returns whether or not the given data flavor is supported.
*
* @param df the <code>DataFlavor</code> to test
* @return whether or not the given flavor is supported.
*/
public boolean isDataFlavorSupported(DataFlavor df) {
if (isDrop) {
if (source instanceof DropTargetDragEvent) {
return ((DropTargetDragEvent)source).isDataFlavorSupported(df);
} else {
return ((DropTargetDropEvent)source).isDataFlavorSupported(df);
}
}
return ((Transferable)source).isDataFlavorSupported(df);
}
/**
* Returns the <code>Transferable</code> associated with this transfer.
* <p>
* Note: Unless it is necessary to fetch the <code>Transferable</code>
* directly, use one of the other methods on this class to inquire about
* the transfer. This may perform better than fetching the
* <code>Transferable</code> and asking it directly.
*
* @return the <code>Transferable</code> associated with this transfer
*/
public Transferable getTransferable() {
if (isDrop) {
if (source instanceof DropTargetDragEvent) {
return ((DropTargetDragEvent)source).getTransferable();
} else {
return ((DropTargetDropEvent)source).getTransferable();
}
}
return (Transferable)source;
}
}
/**
* Returns an {@code Action} that performs cut operations to the
* clipboard. When performed, this action operates on the {@code JComponent}
* source of the {@code ActionEvent} by invoking {@code exportToClipboard},
* with a {@code MOVE} action, on the component's {@code TransferHandler}.
*
* @return an {@code Action} for performing cuts to the clipboard
*/
public static Action getCutAction() {
return cutAction;
}
/**
* Returns an {@code Action} that performs copy operations to the
* clipboard. When performed, this action operates on the {@code JComponent}
* source of the {@code ActionEvent} by invoking {@code exportToClipboard},
* with a {@code COPY} action, on the component's {@code TransferHandler}.
*
* @return an {@code Action} for performing copies to the clipboard
*/
public static Action getCopyAction() {
return copyAction;
}
/**
* Returns an {@code Action} that performs paste operations from the
* clipboard. When performed, this action operates on the {@code JComponent}
* source of the {@code ActionEvent} by invoking {@code importData},
* with the clipboard contents, on the component's {@code TransferHandler}.
*
* @return an {@code Action} for performing pastes from the clipboard
*/
public static Action getPasteAction() {
return pasteAction;
}
/**
* Constructs a transfer handler that can transfer a Java Bean property
* from one component to another via the clipboard or a drag and drop
* operation.
*
* @param property the name of the property to transfer; this can
* be <code>null</code> if there is no property associated with the transfer
* handler (a subclass that performs some other kind of transfer, for example)
*/
public TransferHandler(String property) {
propertyName = property;
}
/**
* Convenience constructor for subclasses.
*/
protected TransferHandler() {
this(null);
}
/**
* image for the {@code startDrag} method
*
* @see java.awt.dnd.DragGestureEvent#startDrag(Cursor dragCursor, Image dragImage, Point imageOffset, Transferable transferable, DragSourceListener dsl)
*/
private Image dragImage;
/**
* anchor offset for the {@code startDrag} method
*
* @see java.awt.dnd.DragGestureEvent#startDrag(Cursor dragCursor, Image dragImage, Point imageOffset, Transferable transferable, DragSourceListener dsl)
*/
private Point dragImageOffset;
/**
* Sets the drag image parameter. The image has to be prepared
* for rendering by the moment of the call. The image is stored
* by reference because of some performance reasons.
*
* @param img an image to drag
*/
public void setDragImage(Image img) {
dragImage = img;
}
/**
* Returns the drag image. If there is no image to drag,
* the returned value is {@code null}.
*
* @return the reference to the drag image
*/
public Image getDragImage() {
return dragImage;
}
/**
* Sets an anchor offset for the image to drag.
* It can not be {@code null}.
*
* @param p a {@code Point} object that corresponds
* to coordinates of an anchor offset of the image
* relative to the upper left corner of the image
*/
public void setDragImageOffset(Point p) {
dragImageOffset = new Point(p);
}
/**
* Returns an anchor offset for the image to drag.
*
* @return a {@code Point} object that corresponds
* to coordinates of an anchor offset of the image
* relative to the upper left corner of the image.
* The point {@code (0,0)} returns by default.
*/
public Point getDragImageOffset() {
if (dragImageOffset == null) {
return new Point(0,0);
}
return new Point(dragImageOffset);
}
/**
* Causes the Swing drag support to be initiated. This is called by
* the various UI implementations in the <code>javax.swing.plaf.basic</code>
* package if the dragEnabled property is set on the component.
* This can be called by custom UI
* implementations to use the Swing drag support. This method can also be called
* by a Swing extension written as a subclass of <code>JComponent</code>
* to take advantage of the Swing drag support.
* <p>
* The transfer <em>will not necessarily</em> have been completed at the
* return of this call (i.e. the call does not block waiting for the drop).
* The transfer will take place through the Swing implementation of the
* <code>java.awt.dnd</code> mechanism, requiring no further effort
* from the developer. The <code>exportDone</code> method will be called
* when the transfer has completed.
*
* @param comp the component holding the data to be transferred;
* provided to enable sharing of <code>TransferHandler</code>s
* @param e the event that triggered the transfer
* @param action the transfer action initially requested;
* either {@code COPY}, {@code MOVE} or {@code LINK};
* the DnD system may change the action used during the
* course of the drag operation
*/
public void exportAsDrag(JComponent comp, InputEvent e, int action) {
int srcActions = getSourceActions(comp);
// only mouse events supported for drag operations
if (!(e instanceof MouseEvent)
// only support known actions
|| !(action == COPY || action == MOVE || action == LINK)
// only support valid source actions
|| (srcActions & action) == 0) {
action = NONE;
}
if (action != NONE && !GraphicsEnvironment.isHeadless()) {
if (recognizer == null) {
recognizer = new SwingDragGestureRecognizer(new DragHandler());
}
recognizer.gestured(comp, (MouseEvent)e, srcActions, action);
} else {
exportDone(comp, null, NONE);
}
}
/**
* Causes a transfer from the given component to the
* given clipboard. This method is called by the default cut and
* copy actions registered in a component's action map.
* <p>
* The transfer will take place using the <code>java.awt.datatransfer</code>
* mechanism, requiring no further effort from the developer. Any data
* transfer <em>will</em> be complete and the <code>exportDone</code>
* method will be called with the action that occurred, before this method
* returns. Should the clipboard be unavailable when attempting to place
* data on it, the <code>IllegalStateException</code> thrown by
* {@link Clipboard#setContents(Transferable, ClipboardOwner)} will
* be propagated through this method. However,
* <code>exportDone</code> will first be called with an action
* of <code>NONE</code> for consistency.
*
* @param comp the component holding the data to be transferred;
* provided to enable sharing of <code>TransferHandler</code>s
* @param clip the clipboard to transfer the data into
* @param action the transfer action requested; this should
* be a value of either <code>COPY</code> or <code>MOVE</code>;
* the operation performed is the intersection of the transfer
* capabilities given by getSourceActions and the requested action;
* the intersection may result in an action of <code>NONE</code>
* if the requested action isn't supported
* @throws IllegalStateException if the clipboard is currently unavailable
* @see Clipboard#setContents(Transferable, ClipboardOwner)
*/
public void exportToClipboard(JComponent comp, Clipboard clip, int action)
throws IllegalStateException {
if ((action == COPY || action == MOVE)
&& (getSourceActions(comp) & action) != 0) {
Transferable t = createTransferable(comp);
if (t != null) {
try {
clip.setContents(t, null);
exportDone(comp, t, action);
return;
} catch (IllegalStateException ise) {
exportDone(comp, t, NONE);
throw ise;
}
}
}
exportDone(comp, null, NONE);
}
/**
* Causes a transfer to occur from a clipboard or a drag and
* drop operation. The <code>Transferable</code> to be
* imported and the component to transfer to are contained
* within the <code>TransferSupport</code>.
* <p>
* While the drag and drop implementation calls {@code canImport}
* to determine the suitability of a transfer before calling this
* method, the implementation of paste does not. As such, it cannot
* be assumed that the transfer is acceptable upon a call to
* this method for paste. It is recommended that {@code canImport} be
* explicitly called to cover this case.
* <p>
* Note: The <code>TransferSupport</code> object passed to this method
* is only valid for the duration of the method call. It is undefined
* what values it may contain after this method returns.
*
* @param support the object containing the details of
* the transfer, not <code>null</code>.
* @return true if the data was inserted into the component,
* false otherwise
* @throws NullPointerException if <code>support</code> is {@code null}
* @see #canImport(TransferHandler.TransferSupport)
* @since 1.6
*/
public boolean importData(TransferSupport support) {
return support.getComponent() instanceof JComponent
? importData((JComponent)support.getComponent(), support.getTransferable())
: false;
}
/**
* Causes a transfer to a component from a clipboard or a
* DND drop operation. The <code>Transferable</code> represents
* the data to be imported into the component.
* <p>
* Note: Swing now calls the newer version of <code>importData</code>
* that takes a <code>TransferSupport</code>, which in turn calls this
* method (if the component in the {@code TransferSupport} is a
* {@code JComponent}). Developers are encouraged to call and override the
* newer version as it provides more information (and is the only
* version that supports use with a {@code TransferHandler} set directly
* on a {@code JFrame} or other non-{@code JComponent}).
*
* @param comp the component to receive the transfer;
* provided to enable sharing of <code>TransferHandler</code>s
* @param t the data to import
* @return true if the data was inserted into the component, false otherwise
* @see #importData(TransferHandler.TransferSupport)
*/
public boolean importData(JComponent comp, Transferable t) {
PropertyDescriptor prop = getPropertyDescriptor(comp);
if (prop != null) {
Method writer = prop.getWriteMethod();
if (writer == null) {
// read-only property. ignore
return false;
}
Class<?>[] params = writer.getParameterTypes();
if (params.length != 1) {
// zero or more than one argument, ignore
return false;
}
DataFlavor flavor = getPropertyDataFlavor(params[0], t.getTransferDataFlavors());
if (flavor != null) {
try {
Object value = t.getTransferData(flavor);
Object[] args = { value };
MethodUtil.invoke(writer, comp, args);
return true;
} catch (Exception ex) {
System.err.println("Invocation failed");
// invocation code
}
}
}
return false;
}
/**
* This method is called repeatedly during a drag and drop operation
* to allow the developer to configure properties of, and to return
* the acceptability of transfers; with a return value of {@code true}
* indicating that the transfer represented by the given
* {@code TransferSupport} (which contains all of the details of the
* transfer) is acceptable at the current time, and a value of {@code false}
* rejecting the transfer.
* <p>
* For those components that automatically display a drop location during
* drag and drop, accepting the transfer, by default, tells them to show
* the drop location. This can be changed by calling
* {@code setShowDropLocation} on the {@code TransferSupport}.
* <p>
* By default, when the transfer is accepted, the chosen drop action is that
* picked by the user via their drag gesture. The developer can override
* this and choose a different action, from the supported source
* actions, by calling {@code setDropAction} on the {@code TransferSupport}.
* <p>
* On every call to {@code canImport}, the {@code TransferSupport} contains
* fresh state. As such, any properties set on it must be set on every
* call. Upon a drop, {@code canImport} is called one final time before
* calling into {@code importData}. Any state set on the
* {@code TransferSupport} during that last call will be available in
* {@code importData}.
* <p>
* This method is not called internally in response to paste operations.
* As such, it is recommended that implementations of {@code importData}
* explicitly call this method for such cases and that this method
* be prepared to return the suitability of paste operations as well.
* <p>
* Note: The <code>TransferSupport</code> object passed to this method
* is only valid for the duration of the method call. It is undefined
* what values it may contain after this method returns.
*
* @param support the object containing the details of
* the transfer, not <code>null</code>.
* @return <code>true</code> if the import can happen,
* <code>false</code> otherwise
* @throws NullPointerException if <code>support</code> is {@code null}
* @see #importData(TransferHandler.TransferSupport)
* @see javax.swing.TransferHandler.TransferSupport#setShowDropLocation
* @see javax.swing.TransferHandler.TransferSupport#setDropAction
* @since 1.6
*/
public boolean canImport(TransferSupport support) {
return support.getComponent() instanceof JComponent
? canImport((JComponent)support.getComponent(), support.getDataFlavors())
: false;
}
/**
* Indicates whether a component will accept an import of the given
* set of data flavors prior to actually attempting to import it.
* <p>
* Note: Swing now calls the newer version of <code>canImport</code>
* that takes a <code>TransferSupport</code>, which in turn calls this
* method (only if the component in the {@code TransferSupport} is a
* {@code JComponent}). Developers are encouraged to call and override the
* newer version as it provides more information (and is the only
* version that supports use with a {@code TransferHandler} set directly
* on a {@code JFrame} or other non-{@code JComponent}).
*
* @param comp the component to receive the transfer;
* provided to enable sharing of <code>TransferHandler</code>s
* @param transferFlavors the data formats available
* @return true if the data can be inserted into the component, false otherwise
* @see #canImport(TransferHandler.TransferSupport)
*/
public boolean canImport(JComponent comp, DataFlavor[] transferFlavors) {
PropertyDescriptor prop = getPropertyDescriptor(comp);
if (prop != null) {
Method writer = prop.getWriteMethod();
if (writer == null) {
// read-only property. ignore
return false;
}
Class<?>[] params = writer.getParameterTypes();
if (params.length != 1) {
// zero or more than one argument, ignore
return false;
}
DataFlavor flavor = getPropertyDataFlavor(params[0], transferFlavors);
if (flavor != null) {
return true;
}
}
return false;
}
/**
* Returns the type of transfer actions supported by the source;
* any bitwise-OR combination of {@code COPY}, {@code MOVE}
* and {@code LINK}.
* <p>
* Some models are not mutable, so a transfer operation of {@code MOVE}
* should not be advertised in that case. Returning {@code NONE}
* disables transfers from the component.
*
* @param c the component holding the data to be transferred;
* provided to enable sharing of <code>TransferHandler</code>s
* @return {@code COPY} if the transfer property can be found,
* otherwise returns <code>NONE</code>
*/
public int getSourceActions(JComponent c) {
PropertyDescriptor prop = getPropertyDescriptor(c);
if (prop != null) {
return COPY;
}
return NONE;
}
/**
* Returns an object that establishes the look of a transfer. This is
* useful for both providing feedback while performing a drag operation and for
* representing the transfer in a clipboard implementation that has a visual
* appearance. The implementation of the <code>Icon</code> interface should
* not alter the graphics clip or alpha level.
* The icon implementation need not be rectangular or paint all of the
* bounding rectangle and logic that calls the icons paint method should
* not assume the all bits are painted. <code>null</code> is a valid return value
* for this method and indicates there is no visual representation provided.
* In that case, the calling logic is free to represent the
* transferable however it wants.
* <p>
* The default Swing logic will not do an alpha blended drag animation if
* the return is <code>null</code>.
*
* @param t the data to be transferred; this value is expected to have been
* created by the <code>createTransferable</code> method
* @return <code>null</code>, indicating
* there is no default visual representation
*/
public Icon getVisualRepresentation(Transferable t) {
return null;
}
/**
* Creates a <code>Transferable</code> to use as the source for
* a data transfer. Returns the representation of the data to
* be transferred, or <code>null</code> if the component's
* property is <code>null</code>
*
* @param c the component holding the data to be transferred;
* provided to enable sharing of <code>TransferHandler</code>s
* @return the representation of the data to be transferred, or
* <code>null</code> if the property associated with <code>c</code>
* is <code>null</code>
*
*/
protected Transferable createTransferable(JComponent c) {
PropertyDescriptor property = getPropertyDescriptor(c);
if (property != null) {
return new PropertyTransferable(property, c);
}
return null;
}
/**
* Invoked after data has been exported. This method should remove
* the data that was transferred if the action was <code>MOVE</code>.
* <p>
* This method is implemented to do nothing since <code>MOVE</code>
* is not a supported action of this implementation
* (<code>getSourceActions</code> does not include <code>MOVE</code>).
*
* @param source the component that was the source of the data
* @param data The data that was transferred or possibly null
* if the action is <code>NONE</code>.
* @param action the actual action that was performed
*/
protected void exportDone(JComponent source, Transferable data, int action) {
}
/**
* Fetches the property descriptor for the property assigned to this transfer
* handler on the given component (transfer handler may be shared). This
* returns <code>null</code> if the property descriptor can't be found
* or there is an error attempting to fetch the property descriptor.
*/
private PropertyDescriptor getPropertyDescriptor(JComponent comp) {
if (propertyName == null) {
return null;
}
Class<?> k = comp.getClass();
BeanInfo bi;
try {
bi = Introspector.getBeanInfo(k);
} catch (IntrospectionException ex) {
return null;
}
PropertyDescriptor props[] = bi.getPropertyDescriptors();
for (int i=0; i < props.length; i++) {
if (propertyName.equals(props[i].getName())) {
Method reader = props[i].getReadMethod();
if (reader != null) {
Class<?>[] params = reader.getParameterTypes();
if (params == null || params.length == 0) {
// found the desired descriptor
return props[i];
}
}
}
}
return null;
}
/**
* Fetches the data flavor from the array of possible flavors that
* has data of the type represented by property type. Null is
* returned if there is no match.
*/
private DataFlavor getPropertyDataFlavor(Class<?> k, DataFlavor[] flavors) {
for(int i = 0; i < flavors.length; i++) {
DataFlavor flavor = flavors[i];
if ("application".equals(flavor.getPrimaryType()) &&
"x-java-jvm-local-objectref".equals(flavor.getSubType()) &&
k.isAssignableFrom(flavor.getRepresentationClass())) {
return flavor;
}
}
return null;
}
private String propertyName;
private static SwingDragGestureRecognizer recognizer = null;
private static DropTargetListener getDropTargetListener() {
synchronized(DropHandler.class) {
DropHandler handler =
(DropHandler)AppContext.getAppContext().get(DropHandler.class);
if (handler == null) {
handler = new DropHandler();
AppContext.getAppContext().put(DropHandler.class, handler);
}
return handler;
}
}
static class PropertyTransferable implements Transferable {
PropertyTransferable(PropertyDescriptor p, JComponent c) {
property = p;
component = c;
}
// --- Transferable methods ----------------------------------------------
/**
* Returns an array of <code>DataFlavor</code> objects indicating the flavors the data
* can be provided in. The array should be ordered according to preference
* for providing the data (from most richly descriptive to least descriptive).
* @return an array of data flavors in which this data can be transferred
*/
public DataFlavor[] getTransferDataFlavors() {
DataFlavor[] flavors = new DataFlavor[1];
Class<?> propertyType = property.getPropertyType();
String mimeType = DataFlavor.javaJVMLocalObjectMimeType + ";class=" + propertyType.getName();
try {
flavors[0] = new DataFlavor(mimeType);
} catch (ClassNotFoundException cnfe) {
flavors = new DataFlavor[0];
}
return flavors;
}
/**
* Returns whether the specified data flavor is supported for
* this object.
* @param flavor the requested flavor for the data
* @return true if this <code>DataFlavor</code> is supported,
* otherwise false
*/
public boolean isDataFlavorSupported(DataFlavor flavor) {
Class<?> propertyType = property.getPropertyType();
if ("application".equals(flavor.getPrimaryType()) &&
"x-java-jvm-local-objectref".equals(flavor.getSubType()) &&
flavor.getRepresentationClass().isAssignableFrom(propertyType)) {
return true;
}
return false;
}
/**
* Returns an object which represents the data to be transferred. The class
* of the object returned is defined by the representation class of the flavor.
*
* @param flavor the requested flavor for the data
* @see DataFlavor#getRepresentationClass
* @exception IOException if the data is no longer available
* in the requested flavor.
* @exception UnsupportedFlavorException if the requested data flavor is
* not supported.
*/
public Object getTransferData(DataFlavor flavor) throws UnsupportedFlavorException, IOException {
if (! isDataFlavorSupported(flavor)) {
throw new UnsupportedFlavorException(flavor);
}
Method reader = property.getReadMethod();
Object value = null;
try {
value = MethodUtil.invoke(reader, component, (Object[])null);
} catch (Exception ex) {
throw new IOException("Property read failed: " + property.getName());
}
return value;
}
JComponent component;
PropertyDescriptor property;
}
/**
* This is the default drop target for drag and drop operations if
* one isn't provided by the developer. <code>DropTarget</code>
* only supports one <code>DropTargetListener</code> and doesn't
* function properly if it isn't set.
* This class sets the one listener as the linkage of drop handling
* to the <code>TransferHandler</code>, and adds support for
* additional listeners which some of the <code>ComponentUI</code>
* implementations install to manipulate a drop insertion location.
*/
static class SwingDropTarget extends DropTarget implements UIResource {
SwingDropTarget(Component c) {
super(c, COPY_OR_MOVE | LINK, null);
try {
// addDropTargetListener is overridden
// we specifically need to add to the superclass
super.addDropTargetListener(getDropTargetListener());
} catch (TooManyListenersException tmle) {}
}
public void addDropTargetListener(DropTargetListener dtl) throws TooManyListenersException {
// Since the super class only supports one DropTargetListener,
// and we add one from the constructor, we always add to the
// extended list.
if (listenerList == null) {
listenerList = new EventListenerList();
}
listenerList.add(DropTargetListener.class, dtl);
}
public void removeDropTargetListener(DropTargetListener dtl) {
if (listenerList != null) {
listenerList.remove(DropTargetListener.class, dtl);
}
}
// --- DropTargetListener methods (multicast) --------------------------
public void dragEnter(DropTargetDragEvent e) {
super.dragEnter(e);
if (listenerList != null) {
Object[] listeners = listenerList.getListenerList();
for (int i = listeners.length-2; i>=0; i-=2) {
if (listeners[i]==DropTargetListener.class) {
((DropTargetListener)listeners[i+1]).dragEnter(e);
}
}
}
}
public void dragOver(DropTargetDragEvent e) {
super.dragOver(e);
if (listenerList != null) {
Object[] listeners = listenerList.getListenerList();
for (int i = listeners.length-2; i>=0; i-=2) {
if (listeners[i]==DropTargetListener.class) {
((DropTargetListener)listeners[i+1]).dragOver(e);
}
}
}
}
public void dragExit(DropTargetEvent e) {
super.dragExit(e);
if (listenerList != null) {
Object[] listeners = listenerList.getListenerList();
for (int i = listeners.length-2; i>=0; i-=2) {
if (listeners[i]==DropTargetListener.class) {
((DropTargetListener)listeners[i+1]).dragExit(e);
}
}
}
if (!isActive()) {
// If the Drop target is inactive the dragExit will not be dispatched to the dtListener,
// so make sure that we clean up the dtListener anyway.
DropTargetListener dtListener = getDropTargetListener();
if (dtListener != null && dtListener instanceof DropHandler) {
((DropHandler)dtListener).cleanup(false);
}
}
}
public void drop(DropTargetDropEvent e) {
super.drop(e);
if (listenerList != null) {
Object[] listeners = listenerList.getListenerList();
for (int i = listeners.length-2; i>=0; i-=2) {
if (listeners[i]==DropTargetListener.class) {
((DropTargetListener)listeners[i+1]).drop(e);
}
}
}
}
public void dropActionChanged(DropTargetDragEvent e) {
super.dropActionChanged(e);
if (listenerList != null) {
Object[] listeners = listenerList.getListenerList();
for (int i = listeners.length-2; i>=0; i-=2) {
if (listeners[i]==DropTargetListener.class) {
((DropTargetListener)listeners[i+1]).dropActionChanged(e);
}
}
}
}
private EventListenerList listenerList;
}
private static class DropHandler implements DropTargetListener,
Serializable,
ActionListener {
private Timer timer;
private Point lastPosition;
private Rectangle outer = new Rectangle();
private Rectangle inner = new Rectangle();
private int hysteresis = 10;
private Component component;
private Object state;
private TransferSupport support =
new TransferSupport(null, (DropTargetEvent)null);
private static final int AUTOSCROLL_INSET = 10;
/**
* Update the geometry of the autoscroll region. The geometry is
* maintained as a pair of rectangles. The region can cause
* a scroll if the pointer sits inside it for the duration of the
* timer. The region that causes the timer countdown is the area
* between the two rectangles.
* <p>
* This is implemented to use the visible area of the component
* as the outer rectangle, and the insets are fixed at 10. Should
* the component be smaller than a total of 20 in any direction,
* autoscroll will not occur in that direction.
*/
private void updateAutoscrollRegion(JComponent c) {
// compute the outer
Rectangle visible = c.getVisibleRect();
outer.setBounds(visible.x, visible.y, visible.width, visible.height);
// compute the insets
Insets i = new Insets(0, 0, 0, 0);
if (c instanceof Scrollable) {
int minSize = 2 * AUTOSCROLL_INSET;
if (visible.width >= minSize) {
i.left = i.right = AUTOSCROLL_INSET;
}
if (visible.height >= minSize) {
i.top = i.bottom = AUTOSCROLL_INSET;
}
}
// set the inner from the insets
inner.setBounds(visible.x + i.left,
visible.y + i.top,
visible.width - (i.left + i.right),
visible.height - (i.top + i.bottom));
}
/**
* Perform an autoscroll operation. This is implemented to scroll by the
* unit increment of the Scrollable using scrollRectToVisible. If the
* cursor is in a corner of the autoscroll region, more than one axis will
* scroll.
*/
private void autoscroll(JComponent c, Point pos) {
if (c instanceof Scrollable) {
Scrollable s = (Scrollable) c;
if (pos.y < inner.y) {
// scroll upward
int dy = s.getScrollableUnitIncrement(outer, SwingConstants.VERTICAL, -1);
Rectangle r = new Rectangle(inner.x, outer.y - dy, inner.width, dy);
c.scrollRectToVisible(r);
} else if (pos.y > (inner.y + inner.height)) {
// scroll downard
int dy = s.getScrollableUnitIncrement(outer, SwingConstants.VERTICAL, 1);
Rectangle r = new Rectangle(inner.x, outer.y + outer.height, inner.width, dy);
c.scrollRectToVisible(r);
}
if (pos.x < inner.x) {
// scroll left
int dx = s.getScrollableUnitIncrement(outer, SwingConstants.HORIZONTAL, -1);
Rectangle r = new Rectangle(outer.x - dx, inner.y, dx, inner.height);
c.scrollRectToVisible(r);
} else if (pos.x > (inner.x + inner.width)) {
// scroll right
int dx = s.getScrollableUnitIncrement(outer, SwingConstants.HORIZONTAL, 1);
Rectangle r = new Rectangle(outer.x + outer.width, inner.y, dx, inner.height);
c.scrollRectToVisible(r);
}
}
}
/**
* Initializes the internal properties if they haven't been already
* inited. This is done lazily to avoid loading of desktop properties.
*/
private void initPropertiesIfNecessary() {
if (timer == null) {
Toolkit t = Toolkit.getDefaultToolkit();
Integer prop;
prop = (Integer)
t.getDesktopProperty("DnD.Autoscroll.interval");
timer = new Timer(prop == null ? 100 : prop.intValue(), this);
prop = (Integer)
t.getDesktopProperty("DnD.Autoscroll.initialDelay");
timer.setInitialDelay(prop == null ? 100 : prop.intValue());
prop = (Integer)
t.getDesktopProperty("DnD.Autoscroll.cursorHysteresis");
if (prop != null) {
hysteresis = prop.intValue();
}
}
}
/**
* The timer fired, perform autoscroll if the pointer is within the
* autoscroll region.
* <P>
* @param e the <code>ActionEvent</code>
*/
public void actionPerformed(ActionEvent e) {
updateAutoscrollRegion((JComponent)component);
if (outer.contains(lastPosition) && !inner.contains(lastPosition)) {
autoscroll((JComponent)component, lastPosition);
}
}
// --- DropTargetListener methods -----------------------------------
private void setComponentDropLocation(TransferSupport support,
boolean forDrop) {
DropLocation dropLocation = (support == null)
? null
: support.getDropLocation();
if (SunToolkit.isInstanceOf(component, "javax.swing.text.JTextComponent")) {
state = SwingAccessor.getJTextComponentAccessor().
setDropLocation((JTextComponent)component, dropLocation, state, forDrop);
} else if (component instanceof JComponent) {
state = ((JComponent)component).setDropLocation(dropLocation, state, forDrop);
}
}
private void handleDrag(DropTargetDragEvent e) {
TransferHandler importer =
((HasGetTransferHandler)component).getTransferHandler();
if (importer == null) {
e.rejectDrag();
setComponentDropLocation(null, false);
return;
}
support.setDNDVariables(component, e);
boolean canImport = importer.canImport(support);
if (canImport) {
e.acceptDrag(support.getDropAction());
} else {
e.rejectDrag();
}
boolean showLocation = support.showDropLocationIsSet ?
support.showDropLocation :
canImport;
setComponentDropLocation(showLocation ? support : null, false);
}
public void dragEnter(DropTargetDragEvent e) {
state = null;
component = e.getDropTargetContext().getComponent();
handleDrag(e);
if (component instanceof JComponent) {
lastPosition = e.getLocation();
updateAutoscrollRegion((JComponent)component);
initPropertiesIfNecessary();
}
}
public void dragOver(DropTargetDragEvent e) {
handleDrag(e);
if (!(component instanceof JComponent)) {
return;
}
Point p = e.getLocation();
if (Math.abs(p.x - lastPosition.x) > hysteresis
|| Math.abs(p.y - lastPosition.y) > hysteresis) {
// no autoscroll
if (timer.isRunning()) timer.stop();
} else {
if (!timer.isRunning()) timer.start();
}
lastPosition = p;
}
public void dragExit(DropTargetEvent e) {
cleanup(false);
}
public void drop(DropTargetDropEvent e) {
TransferHandler importer =
((HasGetTransferHandler)component).getTransferHandler();
if (importer == null) {
e.rejectDrop();
cleanup(false);
return;
}
support.setDNDVariables(component, e);
boolean canImport = importer.canImport(support);
if (canImport) {
e.acceptDrop(support.getDropAction());
boolean showLocation = support.showDropLocationIsSet ?
support.showDropLocation :
canImport;
setComponentDropLocation(showLocation ? support : null, false);
boolean success;
try {
success = importer.importData(support);
} catch (RuntimeException re) {
success = false;
}
e.dropComplete(success);
cleanup(success);
} else {
e.rejectDrop();
cleanup(false);
}
}
public void dropActionChanged(DropTargetDragEvent e) {
/*
* Work-around for Linux bug where dropActionChanged
* is called before dragEnter.
*/
if (component == null) {
return;
}
handleDrag(e);
}
private void cleanup(boolean forDrop) {
setComponentDropLocation(null, forDrop);
if (component instanceof JComponent) {
((JComponent)component).dndDone();
}
if (timer != null) {
timer.stop();
}
state = null;
component = null;
lastPosition = null;
}
}
/**
* This is the default drag handler for drag and drop operations that
* use the <code>TransferHandler</code>.
*/
private static class DragHandler implements DragGestureListener, DragSourceListener {
private boolean scrolls;
// --- DragGestureListener methods -----------------------------------
/**
* a Drag gesture has been recognized
*/
public void dragGestureRecognized(DragGestureEvent dge) {
JComponent c = (JComponent) dge.getComponent();
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