1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343
/* * @(#)Label.java 1.59 06/04/07 * * Copyright 2006 Sun Microsystems, Inc. All rights reserved. * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */ 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> * * @version 1.59, 04/07/06 * @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 (getClass()) { 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 && valid) { invalidate(); } } /** * 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 }