/
DragSourceExtensionConnector.java
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/
DragSourceExtensionConnector.java
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/*
* Copyright 2000-2016 Vaadin Ltd.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
package com.vaadin.client.extensions;
import com.google.gwt.dom.client.DataTransfer;
import com.google.gwt.dom.client.Element;
import com.google.gwt.dom.client.NativeEvent;
import com.google.gwt.user.client.ui.Widget;
import com.vaadin.client.ComponentConnector;
import com.vaadin.client.ServerConnector;
import com.vaadin.event.dnd.DragSourceExtension;
import com.vaadin.shared.ui.Connect;
import com.vaadin.shared.ui.dnd.DragSourceRpc;
import com.vaadin.shared.ui.dnd.DragSourceState;
import com.vaadin.shared.ui.dnd.DropEffect;
import elemental.events.Event;
import elemental.events.EventListener;
import elemental.events.EventTarget;
/**
* Extension to add drag source functionality to a widget for using HTML5 drag
* and drop. Client side counterpart of {@link DragSourceExtension}.
*
* @author Vaadin Ltd
* @since 8.1
*/
@Connect(DragSourceExtension.class)
public class DragSourceExtensionConnector extends AbstractExtensionConnector {
private static final String CLASS_DRAGGABLE = "v-draggable";
// Create event listeners
private final EventListener dragStartListener = this::onDragStart;
private final EventListener dragEndListener = this::onDragEnd;
/**
* Widget of the drag source component.
*/
private Widget dragSourceWidget;
@Override
protected void extend(ServerConnector target) {
dragSourceWidget = ((ComponentConnector) target).getWidget();
Element dragSourceElement = getDraggableElement();
dragSourceElement.setDraggable(Element.DRAGGABLE_TRUE);
dragSourceElement.addClassName(CLASS_DRAGGABLE);
EventTarget dragSource = dragSourceElement.cast();
// dragstart
dragSource.addEventListener(Event.DRAGSTART, dragStartListener);
// dragend
dragSource.addEventListener(Event.DRAGEND, dragEndListener);
}
@Override
public void onUnregister() {
super.onUnregister();
EventTarget dragSource = (EventTarget) getDraggableElement();
// Remove listeners
dragSource.removeEventListener(Event.DRAGSTART, dragStartListener);
dragSource.removeEventListener(Event.DRAGEND, dragEndListener);
}
/**
* Event handler for the {@code dragstart} event. Called when {@code
* dragstart} event occurs.
*
* @param event
* browser event to be handled
*/
protected void onDragStart(Event event) {
// Convert elemental event to have access to dataTransfer
NativeEvent nativeEvent = (NativeEvent) event;
// Set effectAllowed parameter
if (getState().effectAllowed != null) {
setEffectAllowed(nativeEvent.getDataTransfer(),
getState().effectAllowed.getValue());
}
// Set text data parameter
nativeEvent.getDataTransfer().setData(DragSourceState.DATA_TYPE_TEXT,
getState().dataTransferText);
// Initiate firing server side dragstart event when there is a
// DragStartListener attached on the server side
if (hasEventListener(DragSourceState.EVENT_DRAGSTART)) {
getRpcProxy(DragSourceRpc.class).dragStart();
}
}
/**
* Event handler for the {@code dragend} event. Called when {@code dragend}
* event occurs.
*
* @param event
* browser event to be handled
*/
protected void onDragEnd(Event event) {
// Initiate server start dragend event when there is a DragEndListener
// attached on the server side
if (hasEventListener(DragSourceState.EVENT_DRAGEND)) {
String dropEffect = getDropEffect(
((NativeEvent) event).getDataTransfer());
assert dropEffect != null : "Drop effect should never be null";
getRpcProxy(DragSourceRpc.class)
.dragEnd(DropEffect.valueOf(dropEffect.toUpperCase()));
}
}
/**
* Finds the draggable element within the widget. By default, returns the
* topmost element.
*
* @return the draggable element in the parent widget.
*/
protected Element getDraggableElement() {
return dragSourceWidget.getElement();
}
private native void setEffectAllowed(DataTransfer dataTransfer,
String effectAllowed)/*-{
dataTransfer.effectAllowed = effectAllowed;
}-*/;
private native String getDropEffect(DataTransfer dataTransfer)/*-{
return dataTransfer.dropEffect;
}-*/;
@Override
public DragSourceState getState() {
return (DragSourceState) super.getState();
}
}