| package org.eclipse.swt.dnd; |
| |
| /* |
| * Copyright (c) 2000, 2002 IBM Corp. All rights reserved. |
| * This file is made available under the terms of the Common Public License v1.0 |
| * which accompanies this distribution, and is available at |
| * http://www.eclipse.org/legal/cpl-v10.html |
| */ |
| |
| import org.eclipse.swt.*; |
| import org.eclipse.swt.widgets.*; |
| |
| /** |
| * |
| * <code>DragSource</code> defines the source object for a drag and drop transfer. |
| * |
| * <p>IMPORTANT: This class is <em>not</em> intended to be subclassed.</p> |
| * |
| * <p>A drag source is the object which originates a drag and drop operation. For the specified widget, |
| * it defines the type of data that is available for dragging and the set of operations that can |
| * be performed on that data. The operations can be any bit-wise combination of DND.MOVE, DND.COPY or |
| * DND.LINK. The type of data that can be transferred is specified by subclasses of Transfer such as |
| * TextTransfer or FileTransfer. The type of data transferred can be a predefined system type or it |
| * can be a type defined by the application. For instructions on how to define your own transfer type, |
| * refer to <code>ByteArrayTransfer</code>.</p> |
| * |
| * <p>You may have several DragSources in an application but you can only have one DragSource |
| * per Control. Data dragged from this DragSource can be dropped on a site within this application |
| * or it can be dropped on another application such as an external Text editor.</p> |
| * |
| * <p>The application supplies the content of the data being transferred by implementing the |
| * <code>DragSourceListener</code> and associating it with the DragSource via DragSource#addDragListener.</p> |
| * |
| * <p>When a successful move operation occurs, the application is required to take the appropriate |
| * action to remove the data from its display and remove any associated operating system resources or |
| * internal references. Typically in a move operation, the drop target makes a copy of the data |
| * and the drag source deletes the original. However, sometimes copying the data can take a long |
| * time (such as copying a large file). Therefore, on some platforms, the drop target may actually |
| * move the data in the operating system rather than make a copy. This is usually only done in |
| * file transfers. In this case, the drag source is informed in the DragEnd event that a |
| * DROP_TARGET_MOVE was performed. It is the responsibility of the drag source at this point to clean |
| * up its displayed information. No action needs to be taken on the operating system resources.</p> |
| * |
| * <p> The following example shows a Label widget that allows text to be dragged from it.</p> |
| * |
| * <code><pre> |
| * // Enable a label as a Drag Source |
| * Label label = new Label(shell, SWT.NONE); |
| * // This example will allow text to be dragged |
| * Transfer[] types = new Transfer[] {TextTransfer.getInstance()}; |
| * // This example will allow the text to be copied or moved to the drop target |
| * int operations = DND.DROP_MOVE | DND.DROP_COPY; |
| * |
| * DragSource source = new DragSource (label, operations); |
| * source.setTransfer(types); |
| * source.addDragListener (new DragSourceListener() { |
| * public void dragStart(DragSourceEvent e) { |
| * // Only start the drag if there is actually text in the |
| * // label - this text will be what is dropped on the target. |
| * if (label.getText().length() == 0) { |
| * event.doit = false; |
| * } |
| * }; |
| * public void dragSetData (DragSourceEvent event) { |
| * // A drop has been performed, so provide the data of the |
| * // requested type. |
| * // (Checking the type of the requested data is only |
| * // necessary if the drag source supports more than |
| * // one data type but is shown here as an example). |
| * if (TextTransfer.getInstance().isSupportedType(event.dataType)){ |
| * event.data = label.getText(); |
| * } |
| * } |
| * public void dragFinished(DragSourceEvent event) { |
| * // A Move operation has been performed so remove the data |
| * // from the source |
| * if (event.detail == DND.DROP_MOVE) |
| * label.setText(""); |
| * } |
| * }); |
| * </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.DragStart, DND.DragSetData, DND.DragEnd</dd> |
| * </dl> |
| */ |
| public final class DragSource extends Widget { |
| |
| // info for registering as a drag source |
| private Control control; |
| private Listener controlListener; |
| private Transfer[] transferAgents = new Transfer[0]; |
| |
| private static final String DRAGSOURCEID = "DragSource"; |
| |
| /** |
| * Creates a new <code>DragSource</code> to handle dragging from the specified <code>Control</code>. |
| * Creating an instance of a DragSource may cause system resources to be allocated depending on the platform. |
| * It is therefore mandatory that the DragSource instance be disposed when no longer required. |
| * |
| * @param control the <code>Control</code> that the user clicks on to initiate the drag |
| * @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> |
| * |
| * @see DragSource#dispose |
| * @see DragSource#checkSubclass |
| * @see DND#DROP_NONE |
| * @see DND#DROP_COPY |
| * @see DND#DROP_MOVE |
| * @see DND#DROP_LINK |
| */ |
| public DragSource(Control control, int style) { |
| super (control, style); |
| this.control = control; |
| if (control.getData(DRAGSOURCEID) != null) |
| DND.error(DND.ERROR_CANNOT_INIT_DRAG); |
| |
| controlListener = new Listener () { |
| public void handleEvent (Event event) { |
| if (event.type == SWT.Dispose){ |
| DragSource.this.dispose(); |
| } |
| } |
| }; |
| control.addListener (SWT.Dispose, controlListener); |
| |
| this.addListener(SWT.Dispose, new Listener() { |
| public void handleEvent(Event e) { |
| onDispose(); |
| } |
| }); |
| } |
| |
| /** |
| * 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>DragSourceListener</code> |
| * interface. |
| * |
| * <p><ul> |
| * <li><code>dragStart</code> is called when the user has begun the actions required to drag the widget. |
| * This event gives the application the chance to decide if a drag should be started. |
| * <li><code>dragSetData</code> is called when the data is required from the drag source. |
| * <li><code>dragFinished</code> is called when the drop has successfully completed (mouse up |
| * over a valid target) or has been terminated (such as hitting the ESC key). Perform cleanup |
| * such as removing data from the source side on a successful move operation. |
| * </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 DragSourceListener |
| * @see #removeDragListener |
| * @see DragSourceEvent |
| */ |
| public void addDragListener(DragSourceListener listener) { |
| if (listener == null) DND.error (SWT.ERROR_NULL_ARGUMENT); |
| DNDListener typedListener = new DNDListener (listener); |
| addListener (DND.DragStart, typedListener); |
| addListener (DND.DragEnd, typedListener); |
| addListener (DND.DragSetData, typedListener); |
| } |
| |
| protected void checkSubclass () { |
| String name = getClass().getName (); |
| String validName = DragSource.class.getName(); |
| if (!validName.equals(name)) { |
| DND.error (SWT.ERROR_INVALID_SUBCLASS); |
| } |
| } |
| |
| /** |
| * Returns the Control which is registered for this DragSource. This is the control that the |
| * user clicks in to initiate dragging. |
| * |
| * @return the Control which is registered for this DragSource |
| */ |
| public Control getControl () { |
| return control; |
| } |
| |
| public Display getDisplay () { |
| if (control == null) DND.error(SWT.ERROR_WIDGET_DISPOSED); |
| return control.getDisplay (); |
| } |
| /** |
| * Returns the list of data types that can be transferred by this DragSource. |
| * |
| * @return the list of data types that can be transferred by this DragSource |
| */ |
| public Transfer[] getTransfer(){ |
| return transferAgents; |
| } |
| |
| private void onDispose () { |
| if (control != null && controlListener != null){ |
| control.removeListener(SWT.Dispose, controlListener); |
| control.removeListener(SWT.DragDetect, controlListener); |
| } |
| controlListener = null; |
| control.setData(DRAGSOURCEID, null); |
| control = null; |
| |
| transferAgents = null; |
| } |
| |
| /** |
| * 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 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 DragSourceListener |
| * @see #addDragListener |
| */ |
| public void removeDragListener(DragSourceListener listener) { |
| if (listener == null) DND.error (SWT.ERROR_NULL_ARGUMENT); |
| removeListener (DND.DragStart, listener); |
| removeListener (DND.DragEnd, listener); |
| removeListener (DND.DragSetData, listener); |
| } |
| |
| /** |
| * Specifies the list of data types that can be transferred by this DragSource. |
| * The application must be able to provide data to match each of these types when |
| * a successful drop has occurred. |
| * |
| * @param transferAgents a list of Transfer objects which define the types of data that can be |
| * dragged from this source |
| */ |
| public void setTransfer(Transfer[] transferAgents){ |
| this.transferAgents = transferAgents; |
| } |
| |
| } |