/*
* 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.ui.dd;
import com.google.gwt.dom.client.NativeEvent;
import com.google.gwt.event.dom.client.KeyCodes;
import com.google.gwt.event.shared.HandlerRegistration;
import com.google.gwt.user.client.Event;
import com.google.gwt.user.client.Event.NativePreviewEvent;
import com.google.gwt.user.client.Event.NativePreviewHandler;
import com.google.gwt.user.client.Timer;
import com.google.gwt.user.client.ui.RootPanel;
import com.vaadin.client.WidgetUtil;
import com.vaadin.client.widgets.Grid;
/**
* A simple event handler for elements that can be drag and dropped. Properly
* handles drag start, cancel and end. For example, used in {@link Grid} column
* header reordering.
* <p>
* The showing of the dragged element, drag hints and reacting to drop/cancel is
* delegated to {@link DragAndDropCallback} implementation.
*
* @since 7.5.0
* @author Vaadin Ltd
*/
public class DragAndDropHandler {
/**
* Callback interface for drag and drop.
*/
public interface DragAndDropCallback {
/**
* Called when the drag has started. The drag can be canceled by
* returning {@code false}.
*
* @param e
* the original event that started the drag
* @return {@code true} if the drag is OK to start, {@code false} to
* cancel
*/
boolean onDragStart(Event e);
/**
* Called on drag.
*
* @param e
* the event related to the drag
*/
void onDragUpdate(Event e);
/**
* Called after the has ended on a drop or cancel.
*/
void onDragEnd();
/**
* Called when the drag has ended on a drop.
*/
void onDrop();
/**
* Called when the drag has been canceled.
*/
void onDragCancel();
}
private HandlerRegistration startPreviewHandler;
private HandlerRegistration dragHandlerRegistration;
private DragAndDropCallback callback;
private boolean dragging;
// XXX: This is a hack to stop a click event from propagating through to the
// client once dragging has completed. In the Grid case, this caused
// erroneous selections and/or sorting events.
private Timer stopTimer = new Timer() {
@Override
public void run() {
Event.releaseCapture(RootPanel.getBodyElement());
if (callback != null) {
callback.onDragEnd();
callback = null;
}
if (dragHandlerRegistration != null) {
dragHandlerRegistration.removeHandler();
dragHandlerRegistration = null;
}
dragging = false;
}
};
private final NativePreviewHandler dragPreviewHandler = new NativePreviewHandler() {
@Override
public void onPreviewNativeEvent(NativePreviewEvent event) {
if (dragging) {
final int typeInt = event.getTypeInt();
switch (typeInt) {
case Event.ONMOUSEMOVE:
case Event.ONTOUCHMOVE:
callback.onDragUpdate(Event.as(event.getNativeEvent()));
break;
case Event.ONKEYDOWN:
// End drag if ESC is pressed
int keyCode = event.getNativeEvent().getKeyCode();
if (keyCode == KeyCodes.KEY_ESCAPE) {
cancelDrag(event);
}
break;
case Event.ONTOUCHCANCEL:
cancelDrag(event);
break;
case Event.ONTOUCHEND:
case Event.ONMOUSEUP:
callback.onDragUpdate(Event.as(event.getNativeEvent()));
callback.onDrop();
stopDrag();
break;
case Event.ONCLICK:
break;
default:
break;
}
} else {
stopDrag();
}
// Kill events - as long as this thing is active, we don't want to
// let any event through.
event.getNativeEvent().stopPropagation();
event.getNativeEvent().preventDefault();
event.cancel();
}
};
/**
* This method can be called to trigger drag and drop on any grid element
* that can be dragged and dropped.
*
* @param dragStartingEvent
* the drag triggering event, usually a {@link Event#ONMOUSEDOWN}
* or {@link Event#ONTOUCHSTART} event on the draggable element
*
* @param callback
* the callback that will handle actual drag and drop related
* operations
*/
public void onDragStartOnDraggableElement(
final NativeEvent dragStartingEvent,
final DragAndDropCallback callback) {
startPreviewHandler = Event
.addNativePreviewHandler(new NativePreviewHandler() {
private int startX = WidgetUtil
.getTouchOrMouseClientX(dragStartingEvent);
private int startY = WidgetUtil
.getTouchOrMouseClientY(dragStartingEvent);
@Override
public void onPreviewNativeEvent(NativePreviewEvent event) {
final int typeInt = event.getTypeInt();
if (typeInt == -1 && event.getNativeEvent().getType()
.toLowerCase().contains("pointer")) {
/*
* Ignore PointerEvents since IE10 and IE11 send
* also MouseEvents for backwards compatibility.
*/
return;
}
switch (typeInt) {
case Event.ONMOUSEOVER:
case Event.ONMOUSEOUT:
// we don't care
break;
case Event.ONKEYDOWN:
case Event.ONKEYPRESS:
case Event.ONKEYUP:
case Event.ONBLUR:
case Event.ONFOCUS:
// don't cancel possible drag start
break;
case Event.ONMOUSEMOVE:
case Event.ONTOUCHMOVE:
int currentX = WidgetUtil.getTouchOrMouseClientX(
event.getNativeEvent());
int currentY = WidgetUtil.getTouchOrMouseClientY(
event.getNativeEvent());
if (Math.abs(startX - currentX) > 3
|| Math.abs(startY - currentY) > 3) {
removeStartPreviewHandler();
startDrag(dragStartingEvent, event, callback);
}
event.getNativeEvent().stopPropagation();
event.getNativeEvent().preventDefault();
event.cancel();
break;
default:
// on any other events, clean up this preview
// listener
removeStartPreviewHandler();
break;
}
}
});
}
private void startDrag(NativeEvent startEvent,
NativePreviewEvent triggerEvent, DragAndDropCallback callback) {
if (callback.onDragStart(Event.as(startEvent))) {
this.callback = callback;
dragging = true;
// just capture something to prevent text selection in IE
Event.setCapture(RootPanel.getBodyElement());
dragHandlerRegistration = Event
.addNativePreviewHandler(dragPreviewHandler);
callback.onDragUpdate(Event.as(triggerEvent.getNativeEvent()));
}
}
private void stopDrag() {
if (!stopTimer.isRunning()) {
stopTimer.schedule(100);
}
}
private void cancelDrag(NativePreviewEvent event) {
callback.onDragCancel();
callback.onDragEnd();
stopDrag();
}
private void removeStartPreviewHandler() {
if (startPreviewHandler != null) {
startPreviewHandler.removeHandler();
startPreviewHandler = null;
}
}
}