Java tutorial
/******************************************************************************* * Copyright (c) 2000, 2015 IBM Corporation and others. * All rights reserved. This program and the accompanying materials * are made available under the terms of the Eclipse Public License v1.0 * which accompanies this distribution, and is available at * http://www.eclipse.org/legal/epl-v10.html * * Contributors: * IBM Corporation - initial API and implementation * EclipseSource - adaptation to RAP *******************************************************************************/ package org.eclipse.swt.dnd; import org.eclipse.rap.rwt.internal.lifecycle.WidgetLCA; import org.eclipse.swt.SWT; import org.eclipse.swt.SWTError; import org.eclipse.swt.SWTException; import org.eclipse.swt.internal.dnd.droptargetkit.DropTargetLCA; import org.eclipse.swt.widgets.Control; import org.eclipse.swt.widgets.Event; import org.eclipse.swt.widgets.Listener; import org.eclipse.swt.widgets.Widget; /** * * Class <code>DropTarget</code> defines the target object for a drag and drop transfer. * * <p>IMPORTANT: This class is <em>not</em> intended to be subclassed.</p> * * <p>This class identifies the <code>Control</code> over which the user must position the cursor * in order to drop the data being transferred. It also specifies what data types can be dropped on * this control and what operations can be performed. You may have several DropTragets in an * application but there can only be a one to one mapping between a <code>Control</code> and a <code>DropTarget</code>. * The DropTarget can receive data from within the same application or from other applications * (such as text dragged from a text editor like Word).</p> * * <code><pre> * int operations = DND.DROP_MOVE | DND.DROP_COPY | DND.DROP_LINK; * Transfer[] types = new Transfer[] {TextTransfer.getInstance()}; * DropTarget target = new DropTarget(label, operations); * target.setTransfer(types); * </code></pre> * * <p>The application is notified of data being dragged over this control and of when a drop occurs by * implementing the interface <code>DropTargetListener</code> which uses the class * <code>DropTargetEvent</code>. The application can modify the type of drag being performed * on this Control at any stage of the drag by modifying the <code>event.detail</code> field or the * <code>event.currentDataType</code> field. When the data is dropped, it is the responsibility of * the application to copy this data for its own purposes. * * <code><pre> * target.addDropListener (new DropTargetListener() { * public void dragEnter(DropTargetEvent event) {}; * public void dragOver(DropTargetEvent event) {}; * public void dragLeave(DropTargetEvent event) {}; * public void dragOperationChanged(DropTargetEvent event) {}; * public void dropAccept(DropTargetEvent event) {} * public void drop(DropTargetEvent event) { * // A drop has occurred, copy over the data * if (event.data == null) { // no data to copy, indicate failure in event.detail * event.detail = DND.DROP_NONE; * return; * } * label.setText ((String) event.data); // data copied to label text * } * }); * </pre></code> * * <dl> * <dt><b>Styles</b></dt> <dd>DND.DROP_NONE, DND.DROP_COPY, DND.DROP_MOVE, DND.DROP_LINK</dd> * <dt><b>Events</b></dt> <dd>DND.DragEnter, DND.DragLeave, DND.DragOver, DND.DragOperationChanged, * DND.DropAccept, DND.Drop </dd> * </dl> * * @noextend This class is not intended to be subclassed by clients. * @since 1.3 */ public class DropTarget extends Widget { Control control; Listener controlListener; Transfer[] transferAgents = new Transfer[0]; DropTargetEffect dropEffect; // Track application selections TransferData selectedDataType; int selectedOperation; // workaround - There is no event for "operation changed" so track operation based on key state int keyOperation = -1; static final String DEFAULT_DROP_TARGET_EFFECT = "DEFAULT_DROP_TARGET_EFFECT"; //$NON-NLS-1$ /** * Creates a new <code>DropTarget</code> to allow data to be dropped on the specified * <code>Control</code>. * Creating an instance of a DropTarget may cause system resources to be allocated * depending on the platform. It is therefore mandatory that the DropTarget instance * be disposed when no longer required. * * @param control the <code>Control</code> over which the user positions the cursor to drop the data * @param style the bitwise OR'ing of allowed operations; this may be a combination of any of * DND.DROP_NONE, DND.DROP_COPY, DND.DROP_MOVE, DND.DROP_LINK * * @exception SWTException <ul> * <li>ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the parent</li> * <li>ERROR_INVALID_SUBCLASS - if this class is not an allowed subclass</li> * </ul> * @exception SWTError <ul> * <li>ERROR_CANNOT_INIT_DROP - unable to initiate drop target; this will occur if more than one * drop target is created for a control or if the operating system will not allow the creation * of the drop target</li> * </ul> * * <p>NOTE: ERROR_CANNOT_INIT_DROP should be an SWTException, since it is a * recoverable error, but can not be changed due to backward compatibility.</p> * * @see Widget#dispose * @see DropTarget#checkSubclass * @see DND#DROP_NONE * @see DND#DROP_COPY * @see DND#DROP_MOVE * @see DND#DROP_LINK */ public DropTarget(Control control, int style) { super(control, checkStyle(style)); this.control = control; if (control.getData(DND.DROP_TARGET_KEY) != null) { DND.error(DND.ERROR_CANNOT_INIT_DROP); } control.setData(DND.DROP_TARGET_KEY, this); controlListener = new Listener() { @Override public void handleEvent(Event event) { if (!DropTarget.this.isDisposed()) { DropTarget.this.dispose(); } } }; control.addListener(SWT.Dispose, controlListener); this.addListener(SWT.Dispose, new Listener() { @Override public void handleEvent(Event event) { onDispose(); } }); Object effect = control.getData(DEFAULT_DROP_TARGET_EFFECT); if (effect instanceof DropTargetEffect) { dropEffect = (DropTargetEffect) effect; // } else if (control instanceof Table) { // dropEffect = new TableDropTargetEffect((Table) control); // } else if (control instanceof Tree) { // dropEffect = new TreeDropTargetEffect((Tree) control); } } static int checkStyle(int style) { if (style == SWT.NONE) { return DND.DROP_MOVE; } return style; } /** * Adds the listener to the collection of listeners who will * be notified when a drag and drop operation is in progress, by sending * it one of the messages defined in the <code>DropTargetListener</code> * interface. * * <p><ul> * <li><code>dragEnter</code> is called when the cursor has entered the drop target boundaries * <li><code>dragLeave</code> is called when the cursor has left the drop target boundaries and just before * the drop occurs or is cancelled. * <li><code>dragOperationChanged</code> is called when the operation being performed has changed * (usually due to the user changing the selected modifier key(s) while dragging) * <li><code>dragOver</code> is called when the cursor is moving over the drop target * <li><code>dropAccept</code> is called just before the drop is performed. The drop target is given * the chance to change the nature of the drop or veto the drop by setting the <code>event.detail</code> field * <li><code>drop</code> is called when the data is being dropped * </ul></p> * * @param listener the listener which should be notified * * @exception IllegalArgumentException <ul> * <li>ERROR_NULL_ARGUMENT - if the listener 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> * * @see DropTargetListener * @see #getDropListeners * @see #removeDropListener * @see DropTargetEvent */ public void addDropListener(DropTargetListener listener) { if (listener == null) { DND.error(SWT.ERROR_NULL_ARGUMENT); } DNDListener typedListener = new DNDListener(listener); typedListener.dndWidget = this; addListener(DND.DragEnter, typedListener); addListener(DND.DragLeave, typedListener); addListener(DND.DragOver, typedListener); addListener(DND.DragOperationChanged, typedListener); addListener(DND.Drop, typedListener); addListener(DND.DropAccept, typedListener); } @Override protected void checkSubclass() { String name = getClass().getName(); String validName = DropTarget.class.getName(); if (!validName.equals(name)) { DND.error(SWT.ERROR_INVALID_SUBCLASS); } } /** * Returns the Control which is registered for this DropTarget. This is the control over which the * user positions the cursor to drop the data. * * @return the Control which is registered for this DropTarget */ public Control getControl() { return control; } /** * Returns an array of listeners who will be notified when a drag and drop * operation is in progress, by sending it one of the messages defined in * the <code>DropTargetListener</code> interface. * * @return the listeners who will be notified when a drag and drop * operation is in progress * * @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> * * @see DropTargetListener * @see #addDropListener * @see #removeDropListener * @see DropTargetEvent */ public DropTargetListener[] getDropListeners() { Listener[] listeners = getListeners(DND.DragEnter); int length = listeners.length; DropTargetListener[] dropListeners = new DropTargetListener[length]; int count = 0; for (int i = 0; i < length; i++) { Listener listener = listeners[i]; if (listener instanceof DNDListener) { dropListeners[count] = (DropTargetListener) ((DNDListener) listener).getEventListener(); count++; } } if (count == length) { return dropListeners; } DropTargetListener[] result = new DropTargetListener[count]; System.arraycopy(dropListeners, 0, result, 0, count); return result; } /** * Returns the drop effect for this DropTarget. This drop effect will be * used during a drag and drop to display the drag under effect on the * target widget. * * @return the drop effect that is registered for this DropTarget */ public DropTargetEffect getDropTargetEffect() { return dropEffect; } void onDispose() { if (control == null) { return; } if (controlListener != null) control.removeListener(SWT.Dispose, controlListener); controlListener = null; control.setData(DND.DROP_TARGET_KEY, null); transferAgents = null; control = null; } /** * Returns a list of the data types that can be transferred to this DropTarget. * * @return a list of the data types that can be transferred to this DropTarget */ public Transfer[] getTransfer() { return transferAgents; } /** * Removes the listener from the collection of listeners who will * be notified when a drag and drop operation is in progress. * * @param listener the listener which should no longer be notified * * @exception IllegalArgumentException <ul> * <li>ERROR_NULL_ARGUMENT - if the listener 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> * * @see DropTargetListener * @see #addDropListener * @see #getDropListeners */ public void removeDropListener(DropTargetListener listener) { if (listener == null) { DND.error(SWT.ERROR_NULL_ARGUMENT); } removeListener(DND.DragEnter, listener); removeListener(DND.DragLeave, listener); removeListener(DND.DragOver, listener); removeListener(DND.DragOperationChanged, listener); removeListener(DND.Drop, listener); removeListener(DND.DropAccept, listener); } /** * Specifies the drop effect for this DropTarget. This drop effect will be * used during a drag and drop to display the drag under effect on the * target widget. * * @param effect the drop effect that is registered for this DropTarget */ public void setDropTargetEffect(DropTargetEffect effect) { dropEffect = effect; } /** * Specifies the data types that can be transferred to this DropTarget. If data is * being dragged that does not match one of these types, the drop target will be notified of * the drag and drop operation but the currentDataType will be null and the operation * will be DND.NONE. * * @param transferAgents a list of Transfer objects which define the types of data that can be * dropped on this target * * @exception IllegalArgumentException <ul> * <li>ERROR_NULL_ARGUMENT - if transferAgents is null</li> * </ul> */ public void setTransfer(Transfer[] transferAgents) { if (transferAgents == null) { DND.error(SWT.ERROR_NULL_ARGUMENT); } this.transferAgents = transferAgents; } @Override @SuppressWarnings("unchecked") public <T> T getAdapter(Class<T> adapter) { if (adapter == WidgetLCA.class) { return (T) DropTargetLCA.INSTANCE; } return super.getAdapter(adapter); } }