Back to index...

	/*
	* Copyright (c) 1995, 2013, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/
	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 {
	rowh = moveComponents(target, insets.left + hgap, y,
	maxwidth - x, rowh, start, i, ltr,
	useBaseline, ascent, descent);
	x = d.width;
	y += vgap + rowh;
	rowh = d.height;
	start = i;
	}
	}
	}
	moveComponents(target, insets.left + hgap, y, maxwidth - x, rowh,
	start, nmembers, ltr, useBaseline, ascent, descent);
	}
	}

	//
	// the internal serial version which says which version was written
	// - 0 (default) for versions before the Java 2 platform, v1.2
	// - 1 for version >= Java 2 platform v1.2, which includes "newAlign" field
	//
	private static final int currentSerialVersion = 1;
	/**
	* This represent the <code>currentSerialVersion</code>
	* which is bein used. It will be one of two values :
	* <code>0</code> versions before Java 2 platform v1.2..
	* <code>1</code> versions after Java 2 platform v1.2..
	*
	* @serial
	* @since 1.2
	*/
	private int serialVersionOnStream = currentSerialVersion;

	/**
	* Reads this object out of a serialization stream, handling
	* objects written by older versions of the class that didn't contain all
	* of the fields we use now..
	*/
	private void readObject(ObjectInputStream stream)
	throws IOException, ClassNotFoundException
	{
	stream.defaultReadObject();

	if (serialVersionOnStream < 1) {
	// "newAlign" field wasn't present, so use the old "align" field.
	setAlignment(this.align);
	}
	serialVersionOnStream = currentSerialVersion;
	}

	/**
	* Returns a string representation of this <code>FlowLayout</code>
	* object and its values.
	* @return a string representation of this layout
	*/
	public String toString() {
	String str = "";
	switch (align) {
	case LEFT: str = ",align=left"; break;
	case CENTER: str = ",align=center"; break;
	case RIGHT: str = ",align=right"; break;
	case LEADING: str = ",align=leading"; break;
	case TRAILING: str = ",align=trailing"; break;
	}
	return getClass().getName() + "[hgap=" + hgap + ",vgap=" + vgap + str + "]";
	}


	}

Back to index...