org.eclipse.swt.dnd.DragSource Maven / Gradle / Ivy
/*******************************************************************************
* 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 for 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.dragsourcekit.DragSourceLCA;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Control;
import org.eclipse.swt.widgets.Event;
import org.eclipse.swt.widgets.Listener;
import org.eclipse.swt.widgets.Widget;
/**
*
* DragSource defines the source object for a drag and drop transfer.
*
* IMPORTANT: This class is not intended to be subclassed.
*
* 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 ByteArrayTransfer.
*
* 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.
*
* The application supplies the content of the data being transferred by implementing the
* DragSourceListener and associating it with the DragSource via DragSource#addDragListener.
*
* 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.
*
* The following example shows a Label widget that allows text to be dragged from it.
*
*
* // 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("");
* }
* });
*
* - Styles
- DND.DROP_NONE, DND.DROP_COPY, DND.DROP_MOVE, DND.DROP_LINK
* - Events
- DND.DragStart, DND.DragSetData, DND.DragEnd
*
*
* @noextend This class is not intended to be subclassed by clients.
* @since 1.3
*/
public class DragSource extends Widget {
// info for registering as a drag source
Control control;
Listener controlListener;
Transfer[] transferAgents = new Transfer[ 0 ];
DragSourceEffect dragEffect;
Composite topControl;
// workaround - track the operation performed by the drop target for DragEnd event
int dataEffect = DND.DROP_NONE;
static final String DEFAULT_DRAG_SOURCE_EFFECT = "DEFAULT_DRAG_SOURCE_EFFECT"; //$NON-NLS-1$
static final int CFSTR_PERFORMEDDROPEFFECT = Transfer.registerType( "Performed DropEffect" ); //$NON-NLS-1$
/**
* Creates a new DragSource to handle dragging from the specified Control.
* 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 Control 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
* - ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the parent
* - ERROR_INVALID_SUBCLASS - if this class is not an allowed subclass
*
* @exception SWTError
* - ERROR_CANNOT_INIT_DRAG - unable to initiate drag source; this will occur if more than one
* drag source is created for a control or if the operating system will not allow the creation
* of the drag source
*
*
* NOTE: ERROR_CANNOT_INIT_DRAG should be an SWTException, since it is a
* recoverable error, but can not be changed due to backward compatibility.
*
* @see Widget#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, checkStyle( style ) );
this.control = control;
if( control.getData( DND.DRAG_SOURCE_KEY ) != null ) {
DND.error( DND.ERROR_CANNOT_INIT_DRAG );
}
control.setData( DND.DRAG_SOURCE_KEY, this );
controlListener = new Listener() {
@Override
public void handleEvent( Event event ) {
if( event.type == SWT.Dispose ) {
if( !DragSource.this.isDisposed() ) {
DragSource.this.dispose();
}
}
if( event.type == SWT.DragDetect ) {
if( !DragSource.this.isDisposed() ) {
// DragSource.this.drag(event);
}
}
}
};
control.addListener( SWT.Dispose, controlListener );
control.addListener( SWT.DragDetect, controlListener );
this.addListener( SWT.Dispose, new Listener() {
@Override
public void handleEvent( Event e ) {
DragSource.this.onDispose();
}
} );
Object effect = control.getData( DEFAULT_DRAG_SOURCE_EFFECT );
if( effect instanceof DragSourceEffect ) {
dragEffect = ( DragSourceEffect )effect;
// } else if (control instanceof Tree) {
// dragEffect = new TreeDragSourceEffect((Tree) control);
// } else if (control instanceof Table) {
// dragEffect = new TableDragSourceEffect((Table) 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 DragSourceListener
* interface.
*
*
* dragStart 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.
* dragSetData is called when the data is required from the drag source.
* dragFinished 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.
*
*
* @param listener the listener which should be notified
*
* @exception IllegalArgumentException
* - ERROR_NULL_ARGUMENT - if the listener is null
*
* @exception SWTException
* - ERROR_WIDGET_DISPOSED - if the receiver has been disposed
* - ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
*
*
* @see DragSourceListener
* @see #getDragListeners
* @see #removeDragListener
* @see DragSourceEvent
*/
public void addDragListener( DragSourceListener listener ) {
if( listener == null ) {
DND.error( SWT.ERROR_NULL_ARGUMENT );
}
DNDListener typedListener = new DNDListener( listener );
typedListener.dndWidget = this;
addListener( DND.DragStart, typedListener );
addListener( DND.DragSetData, typedListener );
addListener( DND.DragEnd, typedListener );
}
@Override
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;
}
/**
* 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 DragSourceListener interface.
*
* @return the listeners who will be notified when a drag and drop
* operation is in progress
*
* @exception SWTException
* - ERROR_WIDGET_DISPOSED - if the receiver has been disposed
* - ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
*
*
* @see DragSourceListener
* @see #addDragListener
* @see #removeDragListener
* @see DragSourceEvent
*/
public DragSourceListener[] getDragListeners() {
Listener[] listeners = getListeners( DND.DragStart );
int length = listeners.length;
DragSourceListener[] dragListeners = new DragSourceListener[ length ];
int count = 0;
for( int i = 0; i < length; i++ ) {
Listener listener = listeners[ i ];
if( listener instanceof DNDListener ) {
dragListeners[ count ] = ( DragSourceListener )( ( DNDListener )listener ).getEventListener();
count++ ;
}
}
if( count == length ) {
return dragListeners;
}
DragSourceListener[] result = new DragSourceListener[ count ];
System.arraycopy( dragListeners, 0, result, 0, count );
return result;
}
/**
* Returns the drag effect that is registered for this DragSource. This drag
* effect will be used during a drag and drop operation.
*
* @return the drag effect that is registered for this DragSource
*/
public DragSourceEffect getDragSourceEffect() {
return dragEffect;
}
/**
* 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 ) {
return;
}
if( controlListener != null ) {
control.removeListener( SWT.Dispose, controlListener );
control.removeListener( SWT.DragDetect, controlListener );
}
controlListener = null;
control.setData( DND.DRAG_SOURCE_KEY, 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 no longer be notified
*
* @exception IllegalArgumentException
* - ERROR_NULL_ARGUMENT - if the listener is null
*
* @exception SWTException
* - ERROR_WIDGET_DISPOSED - if the receiver has been disposed
* - ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver
*
*
* @see DragSourceListener
* @see #addDragListener
* @see #getDragListeners
*/
public void removeDragListener( DragSourceListener listener ) {
if( listener == null ) {
DND.error( SWT.ERROR_NULL_ARGUMENT );
}
removeListener( DND.DragStart, listener );
removeListener( DND.DragSetData, listener );
removeListener( DND.DragEnd, listener );
}
/**
* Specifies the drag effect for this DragSource. This drag effect will be
* used during a drag and drop operation.
*
* @param effect the drag effect that is registered for this DragSource
*/
// TODO [rh] investigate if this is useful at all
public void setDragSourceEffect( DragSourceEffect effect ) {
dragEffect = effect;
}
/**
* 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;
}
@Override
@SuppressWarnings( "unchecked" )
public T getAdapter( Class adapter ) {
if( adapter == WidgetLCA.class ) {
return ( T )DragSourceLCA.INSTANCE;
}
return super.getAdapter( adapter );
}
}
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