| /* |
| * Copyright (c) 1995, 2008, 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.awt.peer.LabelPeer; |
| import java.io.IOException; |
| import java.io.ObjectInputStream; |
| import javax.accessibility.*; |
| |
| /** |
| * A <code>Label</code> object is a component for placing text in a |
| * container. A label displays a single line of read-only text. |
| * The text can be changed by the application, but a user cannot edit it |
| * directly. |
| * <p> |
| * For example, the code . . . |
| * <p> |
| * <hr><blockquote><pre> |
| * setLayout(new FlowLayout(FlowLayout.CENTER, 10, 10)); |
| * add(new Label("Hi There!")); |
| * add(new Label("Another Label")); |
| * </pre></blockquote><hr> |
| * <p> |
| * produces the following labels: |
| * <p> |
| * <img src="doc-files/Label-1.gif" alt="Two labels: 'Hi There!' and 'Another label'" |
| * ALIGN=center HSPACE=10 VSPACE=7> |
| * |
| * @author Sami Shaio |
| * @since JDK1.0 |
| */ |
| public class Label extends Component implements Accessible { |
| |
| static { |
| /* ensure that the necessary native libraries are loaded */ |
| Toolkit.loadLibraries(); |
| if (!GraphicsEnvironment.isHeadless()) { |
| initIDs(); |
| } |
| } |
| |
| /** |
| * Indicates that the label should be left justified. |
| */ |
| public static final int LEFT = 0; |
| |
| /** |
| * Indicates that the label should be centered. |
| */ |
| public static final int CENTER = 1; |
| |
| /** |
| * Indicates that the label should be right justified. |
| * @since JDK1.0t. |
| */ |
| public static final int RIGHT = 2; |
| |
| /** |
| * The text of this label. |
| * This text can be modified by the program |
| * but never by the user. |
| * |
| * @serial |
| * @see #getText() |
| * @see #setText(String) |
| */ |
| String text; |
| |
| /** |
| * The label's alignment. The default alignment is set |
| * to be left justified. |
| * |
| * @serial |
| * @see #getAlignment() |
| * @see #setAlignment(int) |
| */ |
| int alignment = LEFT; |
| |
| private static final String base = "label"; |
| private static int nameCounter = 0; |
| |
| /* |
| * JDK 1.1 serialVersionUID |
| */ |
| private static final long serialVersionUID = 3094126758329070636L; |
| |
| /** |
| * Constructs an empty label. |
| * The text of the label is the empty string <code>""</code>. |
| * @exception HeadlessException if GraphicsEnvironment.isHeadless() |
| * returns true. |
| * @see java.awt.GraphicsEnvironment#isHeadless |
| */ |
| public Label() throws HeadlessException { |
| this("", LEFT); |
| } |
| |
| /** |
| * Constructs a new label with the specified string of text, |
| * left justified. |
| * @param text the string that the label presents. |
| * A <code>null</code> value |
| * will be accepted without causing a NullPointerException |
| * to be thrown. |
| * @exception HeadlessException if GraphicsEnvironment.isHeadless() |
| * returns true. |
| * @see java.awt.GraphicsEnvironment#isHeadless |
| */ |
| public Label(String text) throws HeadlessException { |
| this(text, LEFT); |
| } |
| |
| /** |
| * Constructs a new label that presents the specified string of |
| * text with the specified alignment. |
| * Possible values for <code>alignment</code> are <code>Label.LEFT</code>, |
| * <code>Label.RIGHT</code>, and <code>Label.CENTER</code>. |
| * @param text the string that the label presents. |
| * A <code>null</code> value |
| * will be accepted without causing a NullPointerException |
| * to be thrown. |
| * @param alignment the alignment value. |
| * @exception HeadlessException if GraphicsEnvironment.isHeadless() |
| * returns true. |
| * @see java.awt.GraphicsEnvironment#isHeadless |
| */ |
| public Label(String text, int alignment) throws HeadlessException { |
| GraphicsEnvironment.checkHeadless(); |
| this.text = text; |
| setAlignment(alignment); |
| } |
| |
| /** |
| * Read a label from an object input stream. |
| * @exception HeadlessException if |
| * <code>GraphicsEnvironment.isHeadless()</code> returns |
| * <code>true</code> |
| * @serial |
| * @since 1.4 |
| * @see java.awt.GraphicsEnvironment#isHeadless |
| */ |
| private void readObject(ObjectInputStream s) |
| throws ClassNotFoundException, IOException, HeadlessException { |
| GraphicsEnvironment.checkHeadless(); |
| s.defaultReadObject(); |
| } |
| |
| /** |
| * Construct a name for this component. Called by getName() when the |
| * name is <code>null</code>. |
| */ |
| String constructComponentName() { |
| synchronized (Label.class) { |
| return base + nameCounter++; |
| } |
| } |
| |
| /** |
| * Creates the peer for this label. The peer allows us to |
| * modify the appearance of the label without changing its |
| * functionality. |
| */ |
| public void addNotify() { |
| synchronized (getTreeLock()) { |
| if (peer == null) |
| peer = getToolkit().createLabel(this); |
| super.addNotify(); |
| } |
| } |
| |
| /** |
| * Gets the current alignment of this label. Possible values are |
| * <code>Label.LEFT</code>, <code>Label.RIGHT</code>, and |
| * <code>Label.CENTER</code>. |
| * @see java.awt.Label#setAlignment |
| */ |
| public int getAlignment() { |
| return alignment; |
| } |
| |
| /** |
| * Sets the alignment for this label to the specified alignment. |
| * Possible values are <code>Label.LEFT</code>, |
| * <code>Label.RIGHT</code>, and <code>Label.CENTER</code>. |
| * @param alignment the alignment to be set. |
| * @exception IllegalArgumentException if an improper value for |
| * <code>alignment</code> is given. |
| * @see java.awt.Label#getAlignment |
| */ |
| public synchronized void setAlignment(int alignment) { |
| switch (alignment) { |
| case LEFT: |
| case CENTER: |
| case RIGHT: |
| this.alignment = alignment; |
| LabelPeer peer = (LabelPeer)this.peer; |
| if (peer != null) { |
| peer.setAlignment(alignment); |
| } |
| return; |
| } |
| throw new IllegalArgumentException("improper alignment: " + alignment); |
| } |
| |
| /** |
| * Gets the text of this label. |
| * @return the text of this label, or <code>null</code> if |
| * the text has been set to <code>null</code>. |
| * @see java.awt.Label#setText |
| */ |
| public String getText() { |
| return text; |
| } |
| |
| /** |
| * Sets the text for this label to the specified text. |
| * @param text the text that this label displays. If |
| * <code>text</code> is <code>null</code>, it is |
| * treated for display purposes like an empty |
| * string <code>""</code>. |
| * @see java.awt.Label#getText |
| */ |
| public void setText(String text) { |
| boolean testvalid = false; |
| synchronized (this) { |
| if (text != this.text && (this.text == null || |
| !this.text.equals(text))) { |
| this.text = text; |
| LabelPeer peer = (LabelPeer)this.peer; |
| if (peer != null) { |
| peer.setText(text); |
| } |
| testvalid = true; |
| } |
| } |
| |
| // This could change the preferred size of the Component. |
| if (testvalid) { |
| invalidateIfValid(); |
| } |
| } |
| |
| /** |
| * Returns a string representing the state of this <code>Label</code>. |
| * This method is intended to be used only for debugging purposes, and the |
| * content and format of the returned string may vary between |
| * implementations. The returned string may be empty but may not be |
| * <code>null</code>. |
| * |
| * @return the parameter string of this label |
| */ |
| protected String paramString() { |
| String str = ",align="; |
| switch (alignment) { |
| case LEFT: str += "left"; break; |
| case CENTER: str += "center"; break; |
| case RIGHT: str += "right"; break; |
| } |
| return super.paramString() + str + ",text=" + text; |
| } |
| |
| /** |
| * Initialize JNI field and method IDs |
| */ |
| private static native void initIDs(); |
| |
| |
| ///////////////// |
| // Accessibility support |
| //////////////// |
| |
| |
| /** |
| * Gets the AccessibleContext associated with this Label. |
| * For labels, the AccessibleContext takes the form of an |
| * AccessibleAWTLabel. |
| * A new AccessibleAWTLabel instance is created if necessary. |
| * |
| * @return an AccessibleAWTLabel that serves as the |
| * AccessibleContext of this Label |
| * @since 1.3 |
| */ |
| public AccessibleContext getAccessibleContext() { |
| if (accessibleContext == null) { |
| accessibleContext = new AccessibleAWTLabel(); |
| } |
| return accessibleContext; |
| } |
| |
| /** |
| * This class implements accessibility support for the |
| * <code>Label</code> class. It provides an implementation of the |
| * Java Accessibility API appropriate to label user-interface elements. |
| * @since 1.3 |
| */ |
| protected class AccessibleAWTLabel extends AccessibleAWTComponent |
| { |
| /* |
| * JDK 1.3 serialVersionUID |
| */ |
| private static final long serialVersionUID = -3568967560160480438L; |
| |
| public AccessibleAWTLabel() { |
| super(); |
| } |
| |
| /** |
| * Get the accessible name of this object. |
| * |
| * @return the localized name of the object -- can be null if this |
| * object does not have a name |
| * @see AccessibleContext#setAccessibleName |
| */ |
| public String getAccessibleName() { |
| if (accessibleName != null) { |
| return accessibleName; |
| } else { |
| if (getText() == null) { |
| return super.getAccessibleName(); |
| } else { |
| return getText(); |
| } |
| } |
| } |
| |
| /** |
| * Get the role of this object. |
| * |
| * @return an instance of AccessibleRole describing the role of the object |
| * @see AccessibleRole |
| */ |
| public AccessibleRole getAccessibleRole() { |
| return AccessibleRole.LABEL; |
| } |
| |
| } // inner class AccessibleAWTLabel |
| |
| } |
