Java tutorial
/******************************************************************************* * Copyright (c) 2000, 2015 IBM Corporation and others. * * This program and the accompanying materials * are made available under the terms of the Eclipse Public License 2.0 * which accompanies this distribution, and is available at * https://www.eclipse.org/legal/epl-2.0/ * * SPDX-License-Identifier: EPL-2.0 * * Contributors: * IBM Corporation - initial API and implementation *******************************************************************************/ package org.eclipse.swt.widgets; import org.eclipse.swt.*; import org.eclipse.swt.graphics.*; import org.eclipse.swt.internal.*; /** * This class is the abstract superclass of all non-windowed * user interface objects that occur within specific controls. * For example, a tree will contain tree items. * <dl> * <dt><b>Styles:</b></dt> * <dd>(none)</dd> * <dt><b>Events:</b></dt> * <dd>(none)</dd> * </dl> * * @see <a href="http://www.eclipse.org/swt/">Sample code and further information</a> */ public abstract class Item extends Widget { String text; Image image; /** * Maximum number of characters Windows can reliably display in one line. * Mac and Linux can display more but we are limited by windows here. */ static final int TEXT_LIMIT = 8192; static final String ELLIPSIS = "..."; /** * Constructs a new instance of this class given its parent * and a style value describing its behavior and appearance. * The item is added to the end of the items maintained by its parent. * <p> * The style value is either one of the style constants defined in * class <code>SWT</code> which is applicable to instances of this * class, or must be built by <em>bitwise OR</em>'ing together * (that is, using the <code>int</code> "|" operator) two or more * of those <code>SWT</code> style constants. The class description * lists the style constants that are applicable to the class. * Style bits are also inherited from superclasses. * </p> * * @param parent a widget which will be the parent of the new instance (cannot be null) * @param style the style of item to construct * * @exception IllegalArgumentException <ul> * <li>ERROR_NULL_ARGUMENT - if the parent is null</li> * </ul> * @exception SWTException <ul> * <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the parent</li> * </ul> * * @see SWT * @see Widget#getStyle */ public Item(Widget parent, int style) { super(parent, style); text = ""; } /** * Constructs a new instance of this class given its parent * and a style value describing its behavior and appearance, * and the index at which to place it in the items maintained * by its parent. * <p> * The style value is either one of the style constants defined in * class <code>SWT</code> which is applicable to instances of this * class, or must be built by <em>bitwise OR</em>'ing together * (that is, using the <code>int</code> "|" operator) two or more * of those <code>SWT</code> style constants. The class description * lists the style constants that are applicable to the class. * Style bits are also inherited from superclasses. * </p> * * @param parent a widget which will be the parent of the new instance (cannot be null) * @param style the style of item to construct * @param index the zero-relative index at which to store the receiver in its parent * * @exception IllegalArgumentException <ul> * <li>ERROR_NULL_ARGUMENT - if the parent is null</li> * <li>ERROR_INVALID_RANGE - if the index is not between 0 and the number of elements in the parent (inclusive)</li> * </ul> * @exception SWTException <ul> * <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the parent</li> * </ul> * * @see SWT * @see Widget#getStyle */ public Item(Widget parent, int style, int index) { this(parent, style); } @Override protected void checkSubclass() { /* Do Nothing - Subclassing is allowed */ } /** * Returns the receiver's image if it has one, or null * if it does not. * * @return the receiver's image * * @exception SWTException <ul> * <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li> * <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li> * </ul> */ public Image getImage() { checkWidget(); return image; } @Override String getNameText() { return getText(); } /** * Returns the receiver's text, which will be an empty * string if it has never been set. * * @return the receiver's text * * @exception SWTException <ul> * <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li> * <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li> * </ul> */ public String getText() { checkWidget(); return text; } @Override void releaseWidget() { super.releaseWidget(); text = null; image = null; } /** * Sets the receiver's image to the argument, which may be * null indicating that no image should be displayed. * * @param image the image to display on the receiver (may be null) * * @exception IllegalArgumentException <ul> * <li>ERROR_INVALID_ARGUMENT - if the image has been disposed</li> * </ul> * @exception SWTException <ul> * <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li> * <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li> * </ul> */ public void setImage(Image image) { checkWidget(); if (image != null && image.isDisposed()) error(SWT.ERROR_INVALID_ARGUMENT); this.image = image; } /** * Sets the receiver's text. * <p> * Note: If control characters like '\n', '\t' etc. are used * in the string, then the behavior is platform dependent. * </p> * @param string the new text * * @exception IllegalArgumentException <ul> * <li>ERROR_NULL_ARGUMENT - if the text is null</li> * </ul> * @exception SWTException <ul> * <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li> * <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver</li> * </ul> */ public void setText(String string) { checkWidget(); if (string == null) error(SWT.ERROR_NULL_ARGUMENT); text = string; if ((state & HAS_AUTO_DIRECTION) != 0) { updateTextDirection(AUTO_TEXT_DIRECTION); } } boolean updateTextDirection(int textDirection) { /* * textDirection argument passed here is either (1) AUTO_TEXT_DIRECTION, or * (2) 0 (i.e. match orientation) or FLIP_TEXT_DIRECTION (mismatch orientation). */ if (textDirection == AUTO_TEXT_DIRECTION) { state |= HAS_AUTO_DIRECTION; textDirection = (style ^ BidiUtil.resolveTextDirection(text)) == 0 ? 0 : SWT.FLIP_TEXT_DIRECTION; } else { state &= ~HAS_AUTO_DIRECTION; } if (((style & SWT.FLIP_TEXT_DIRECTION) ^ textDirection) != 0) { style ^= SWT.FLIP_TEXT_DIRECTION; return true; } return textDirection == AUTO_TEXT_DIRECTION; } }