JDK8/Java8源码在线阅读
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package java.awt;
import java.io.ObjectInputStream;
import java.io.IOException;
/**
* A flow layout arranges components in a directional flow, much
* like lines of text in a paragraph. The flow direction is
* determined by the container's <code>componentOrientation</code>
* property and may be one of two values:
* <ul>
* <li><code>ComponentOrientation.LEFT_TO_RIGHT</code>
* <li><code>ComponentOrientation.RIGHT_TO_LEFT</code>
* </ul>
* Flow layouts are typically used
* to arrange buttons in a panel. It arranges buttons
* horizontally until no more buttons fit on the same line.
* The line alignment is determined by the <code>align</code>
* property. The possible values are:
* <ul>
* <li>{@link #LEFT LEFT}
* <li>{@link #RIGHT RIGHT}
* <li>{@link #CENTER CENTER}
* <li>{@link #LEADING LEADING}
* <li>{@link #TRAILING TRAILING}
* </ul>
* <p>
* For example, the following picture shows an applet using the flow
* layout manager (its default layout manager) to position three buttons:
* <p>
* <img src="doc-files/FlowLayout-1.gif"
* ALT="Graphic of Layout for Three Buttons"
* style="float:center; margin: 7px 10px;">
* <p>
* Here is the code for this applet:
*
* <hr><blockquote><pre>
* import java.awt.*;
* import java.applet.Applet;
*
* public class myButtons extends Applet {
* Button button1, button2, button3;
* public void init() {
* button1 = new Button("Ok");
* button2 = new Button("Open");
* button3 = new Button("Close");
* add(button1);
* add(button2);
* add(button3);
* }
* }
* </pre></blockquote><hr>
* <p>
* A flow layout lets each component assume its natural (preferred) size.
*
* @author Arthur van Hoff
* @author Sami Shaio
* @since JDK1.0
* @see ComponentOrientation
*/
public class FlowLayout implements LayoutManager, java.io.Serializable {
/**
* This value indicates that each row of components
* should be left-justified.
*/
public static final int LEFT = 0;
/**
* This value indicates that each row of components
* should be centered.
*/
public static final int CENTER = 1;
/**
* This value indicates that each row of components
* should be right-justified.
*/
public static final int RIGHT = 2;
/**
* This value indicates that each row of components
* should be justified to the leading edge of the container's
* orientation, for example, to the left in left-to-right orientations.
*
* @see java.awt.Component#getComponentOrientation
* @see java.awt.ComponentOrientation
* @since 1.2
*/
public static final int LEADING = 3;
/**
* This value indicates that each row of components
* should be justified to the trailing edge of the container's
* orientation, for example, to the right in left-to-right orientations.
*
* @see java.awt.Component#getComponentOrientation
* @see java.awt.ComponentOrientation
* @since 1.2
*/
public static final int TRAILING = 4;
/**
* <code>align</code> is the property that determines
* how each row distributes empty space.
* It can be one of the following values:
* <ul>
* <li><code>LEFT</code>
* <li><code>RIGHT</code>
* <li><code>CENTER</code>
* </ul>
*
* @serial
* @see #getAlignment
* @see #setAlignment
*/
int align; // This is for 1.1 serialization compatibility
/**
* <code>newAlign</code> is the property that determines
* how each row distributes empty space for the Java 2 platform,
* v1.2 and greater.
* It can be one of the following three values:
* <ul>
* <li><code>LEFT</code>
* <li><code>RIGHT</code>
* <li><code>CENTER</code>
* <li><code>LEADING</code>
* <li><code>TRAILING</code>
* </ul>
*
* @serial
* @since 1.2
* @see #getAlignment
* @see #setAlignment
*/
int newAlign; // This is the one we actually use
/**
* The flow layout manager allows a seperation of
* components with gaps. The horizontal gap will
* specify the space between components and between
* the components and the borders of the
* <code>Container</code>.
*
* @serial
* @see #getHgap()
* @see #setHgap(int)
*/
int hgap;
/**
* The flow layout manager allows a seperation of
* components with gaps. The vertical gap will
* specify the space between rows and between the
* the rows and the borders of the <code>Container</code>.
*
* @serial
* @see #getHgap()
* @see #setHgap(int)
*/
int vgap;
/**
* If true, components will be aligned on their baseline.
*/
private boolean alignOnBaseline;
/*
* JDK 1.1 serialVersionUID
*/
private static final long serialVersionUID = -7262534875583282631L;
/**
* Constructs a new <code>FlowLayout</code> with a centered alignment and a
* default 5-unit horizontal and vertical gap.
*/
public FlowLayout() {
this(CENTER, 5, 5);
}
/**
* Constructs a new <code>FlowLayout</code> with the specified
* alignment and a default 5-unit horizontal and vertical gap.
* The value of the alignment argument must be one of
* <code>FlowLayout.LEFT</code>, <code>FlowLayout.RIGHT</code>,
* <code>FlowLayout.CENTER</code>, <code>FlowLayout.LEADING</code>,
* or <code>FlowLayout.TRAILING</code>.
* @param align the alignment value
*/
public FlowLayout(int align) {
this(align, 5, 5);
}
/**
* Creates a new flow layout manager with the indicated alignment
* and the indicated horizontal and vertical gaps.
* <p>
* The value of the alignment argument must be one of
* <code>FlowLayout.LEFT</code>, <code>FlowLayout.RIGHT</code>,
* <code>FlowLayout.CENTER</code>, <code>FlowLayout.LEADING</code>,
* or <code>FlowLayout.TRAILING</code>.
* @param align the alignment value
* @param hgap the horizontal gap between components
* and between the components and the
* borders of the <code>Container</code>
* @param vgap the vertical gap between components
* and between the components and the
* borders of the <code>Container</code>
*/
public FlowLayout(int align, int hgap, int vgap) {
this.hgap = hgap;
this.vgap = vgap;
setAlignment(align);
}
/**
* Gets the alignment for this layout.
* Possible values are <code>FlowLayout.LEFT</code>,
* <code>FlowLayout.RIGHT</code>, <code>FlowLayout.CENTER</code>,
* <code>FlowLayout.LEADING</code>,
* or <code>FlowLayout.TRAILING</code>.
* @return the alignment value for this layout
* @see java.awt.FlowLayout#setAlignment
* @since JDK1.1
*/
public int getAlignment() {
return newAlign;
}
/**
* Sets the alignment for this layout.
* Possible values are
* <ul>
* <li><code>FlowLayout.LEFT</code>
* <li><code>FlowLayout.RIGHT</code>
* <li><code>FlowLayout.CENTER</code>
* <li><code>FlowLayout.LEADING</code>
* <li><code>FlowLayout.TRAILING</code>
* </ul>
* @param align one of the alignment values shown above
* @see #getAlignment()
* @since JDK1.1
*/
public void setAlignment(int align) {
this.newAlign = align;
// this.align is used only for serialization compatibility,
// so set it to a value compatible with the 1.1 version
// of the class
switch (align) {
case LEADING:
this.align = LEFT;
break;
case TRAILING:
this.align = RIGHT;
break;
default:
this.align = align;
break;
}
}
/**
* Gets the horizontal gap between components
* and between the components and the borders
* of the <code>Container</code>
*
* @return the horizontal gap between components
* and between the components and the borders
* of the <code>Container</code>
* @see java.awt.FlowLayout#setHgap
* @since JDK1.1
*/
public int getHgap() {
return hgap;
}
/**
* Sets the horizontal gap between components and
* between the components and the borders of the
* <code>Container</code>.
*
* @param hgap the horizontal gap between components
* and between the components and the borders
* of the <code>Container</code>
* @see java.awt.FlowLayout#getHgap
* @since JDK1.1
*/
public void setHgap(int hgap) {
this.hgap = hgap;
}
/**
* Gets the vertical gap between components and
* between the components and the borders of the
* <code>Container</code>.
*
* @return the vertical gap between components
* and between the components and the borders
* of the <code>Container</code>
* @see java.awt.FlowLayout#setVgap
* @since JDK1.1
*/
public int getVgap() {
return vgap;
}
/**
* Sets the vertical gap between components and between
* the components and the borders of the <code>Container</code>.
*
* @param vgap the vertical gap between components
* and between the components and the borders
* of the <code>Container</code>
* @see java.awt.FlowLayout#getVgap
* @since JDK1.1
*/
public void setVgap(int vgap) {
this.vgap = vgap;
}
/**
* Sets whether or not components should be vertically aligned along their
* baseline. Components that do not have a baseline will be centered.
* The default is false.
*
* @param alignOnBaseline whether or not components should be
* vertically aligned on their baseline
* @since 1.6
*/
public void setAlignOnBaseline(boolean alignOnBaseline) {
this.alignOnBaseline = alignOnBaseline;
}
/**
* Returns true if components are to be vertically aligned along
* their baseline. The default is false.
*
* @return true if components are to be vertically aligned along
* their baseline
* @since 1.6
*/
public boolean getAlignOnBaseline() {
return alignOnBaseline;
}
/**
* Adds the specified component to the layout.
* Not used by this class.
* @param name the name of the component
* @param comp the component to be added
*/
public void addLayoutComponent(String name, Component comp) {
}
/**
* Removes the specified component from the layout.
* Not used by this class.
* @param comp the component to remove
* @see java.awt.Container#removeAll
*/
public void removeLayoutComponent(Component comp) {
}
/**
* Returns the preferred dimensions for this layout given the
* <i>visible</i> components in the specified target container.
*
* @param target the container that needs to be laid out
* @return the preferred dimensions to lay out the
* subcomponents of the specified container
* @see Container
* @see #minimumLayoutSize
* @see java.awt.Container#getPreferredSize
*/
public Dimension preferredLayoutSize(Container target) {
synchronized (target.getTreeLock()) {
Dimension dim = new Dimension(0, 0);
int nmembers = target.getComponentCount();
boolean firstVisibleComponent = true;
boolean useBaseline = getAlignOnBaseline();
int maxAscent = 0;
int maxDescent = 0;
for (int i = 0 ; i < nmembers ; i++) {
Component m = target.getComponent(i);
if (m.isVisible()) {
Dimension d = m.getPreferredSize();
dim.height = Math.max(dim.height, d.height);
if (firstVisibleComponent) {
firstVisibleComponent = false;
} else {
dim.width += hgap;
}
dim.width += d.width;
if (useBaseline) {
int baseline = m.getBaseline(d.width, d.height);
if (baseline >= 0) {
maxAscent = Math.max(maxAscent, baseline);
maxDescent = Math.max(maxDescent, d.height - baseline);
}
}
}
}
if (useBaseline) {
dim.height = Math.max(maxAscent + maxDescent, dim.height);
}
Insets insets = target.getInsets();
dim.width += insets.left + insets.right + hgap*2;
dim.height += insets.top + insets.bottom + vgap*2;
return dim;
}
}
/**
* Returns the minimum dimensions needed to layout the <i>visible</i>
* components contained in the specified target container.
* @param target the container that needs to be laid out
* @return the minimum dimensions to lay out the
* subcomponents of the specified container
* @see #preferredLayoutSize
* @see java.awt.Container
* @see java.awt.Container#doLayout
*/
public Dimension minimumLayoutSize(Container target) {
synchronized (target.getTreeLock()) {
boolean useBaseline = getAlignOnBaseline();
Dimension dim = new Dimension(0, 0);
int nmembers = target.getComponentCount();
int maxAscent = 0;
int maxDescent = 0;
boolean firstVisibleComponent = true;
for (int i = 0 ; i < nmembers ; i++) {
Component m = target.getComponent(i);
if (m.visible) {
Dimension d = m.getMinimumSize();
dim.height = Math.max(dim.height, d.height);
if (firstVisibleComponent) {
firstVisibleComponent = false;
} else {
dim.width += hgap;
}
dim.width += d.width;
if (useBaseline) {
int baseline = m.getBaseline(d.width, d.height);
if (baseline >= 0) {
maxAscent = Math.max(maxAscent, baseline);
maxDescent = Math.max(maxDescent,
dim.height - baseline);
}
}
}
}
if (useBaseline) {
dim.height = Math.max(maxAscent + maxDescent, dim.height);
}
Insets insets = target.getInsets();
dim.width += insets.left + insets.right + hgap*2;
dim.height += insets.top + insets.bottom + vgap*2;
return dim;
}
}
/**
* Centers the elements in the specified row, if there is any slack.
* @param target the component which needs to be moved
* @param x the x coordinate
* @param y the y coordinate
* @param width the width dimensions
* @param height the height dimensions
* @param rowStart the beginning of the row
* @param rowEnd the the ending of the row
* @param useBaseline Whether or not to align on baseline.
* @param ascent Ascent for the components. This is only valid if
* useBaseline is true.
* @param descent Ascent for the components. This is only valid if
* useBaseline is true.
* @return actual row height
*/
private int moveComponents(Container target, int x, int y, int width, int height,
int rowStart, int rowEnd, boolean ltr,
boolean useBaseline, int[] ascent,
int[] descent) {
switch (newAlign) {
case LEFT:
x += ltr ? 0 : width;
break;
case CENTER:
x += width / 2;
break;
case RIGHT:
x += ltr ? width : 0;
break;
case LEADING:
break;
case TRAILING:
x += width;
break;
}
int maxAscent = 0;
int nonbaselineHeight = 0;
int baselineOffset = 0;
if (useBaseline) {
int maxDescent = 0;
for (int i = rowStart ; i < rowEnd ; i++) {
Component m = target.getComponent(i);
if (m.visible) {
if (ascent[i] >= 0) {
maxAscent = Math.max(maxAscent, ascent[i]);
maxDescent = Math.max(maxDescent, descent[i]);
}
else {
nonbaselineHeight = Math.max(m.getHeight(),
nonbaselineHeight);
}
}
}
height = Math.max(maxAscent + maxDescent, nonbaselineHeight);
baselineOffset = (height - maxAscent - maxDescent) / 2;
}
for (int i = rowStart ; i < rowEnd ; i++) {
Component m = target.getComponent(i);
if (m.isVisible()) {
int cy;
if (useBaseline && ascent[i] >= 0) {
cy = y + baselineOffset + maxAscent - ascent[i];
}
else {
cy = y + (height - m.height) / 2;
}
if (ltr) {
m.setLocation(x, cy);
} else {
m.setLocation(target.width - x - m.width, cy);
}
x += m.width + hgap;
}
}
return height;
}
/**
* Lays out the container. This method lets each
* <i>visible</i> component take
* its preferred size by reshaping the components in the
* target container in order to satisfy the alignment of
* this <code>FlowLayout</code> object.
*
* @param target the specified component being laid out
* @see Container
* @see java.awt.Container#doLayout
*/
public void layoutContainer(Container target) {
synchronized (target.getTreeLock()) {
Insets insets = target.getInsets();
int maxwidth = target.width - (insets.left + insets.right + hgap*2);
int nmembers = target.getComponentCount();
int x = 0, y = insets.top + vgap;
int rowh = 0, start = 0;
boolean ltr = target.getComponentOrientation().isLeftToRight();
boolean useBaseline = getAlignOnBaseline();
int[] ascent = null;
int[] descent = null;
if (useBaseline) {
ascent = new int[nmembers];
descent = new int[nmembers];
}
for (int i = 0 ; i < nmembers ; i++) {
Component m = target.getComponent(i);
if (m.isVisible()) {
Dimension d = m.getPreferredSize();
m.setSize(d.width, d.height);
if (useBaseline) {
int baseline = m.getBaseline(d.width, d.height);
if (baseline >= 0) {
ascent[i] = baseline;
descent[i] = d.height - baseline;
}
else {
ascent[i] = -1;
}
}
if ((x == 0) || ((x + d.width) <= maxwidth)) {
if (x > 0) {
x += hgap;
}
x += d.width;
rowh = Math.max(rowh, d.height);
} else {
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