com.google.gwt.event.dom.client.DragDropEventBase Maven / Gradle / Ivy
/*
* Copyright 2011 Google Inc.
*
* 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.google.gwt.event.dom.client;
import com.google.gwt.core.client.GWT;
import com.google.gwt.dom.client.DataTransfer;
import com.google.gwt.dom.client.PartialSupport;
import com.google.gwt.event.shared.EventHandler;
/**
* Base class for drag and drop events.
*
* @param handler type
*/
@PartialSupport
public abstract class DragDropEventBase extends DomEvent {
/**
* Detector for browser support of drag events.
*/
static class DragSupportDetector {
private final boolean isSupported = detectDragSupport();
/**
* Using a run-time check, return true if drag events are supported.
*
* @return true if supported, false otherwise.
*/
public boolean isSupported() {
return isSupported;
}
private native boolean detectDragSupport() /*-{
var elem = document.createElement('div');
elem.setAttribute('ondragstart', 'return;');
return (typeof elem.ondragstart) == "function";
}-*/;
}
/**
* Detector for permutations that do not support drag events.
*/
static class DragSupportDetectorNo extends DragSupportDetector {
@Override
public boolean isSupported() {
return false;
}
}
/**
* The implementation singleton.
*/
private static DragSupportDetector impl;
/**
* Runtime check for whether drag events are supported in this browser.
*
* @return true if supported, false if not
*/
public static boolean isSupported() {
if (impl == null) {
impl = GWT.create(DragSupportDetector.class);
}
return impl.isSupported();
}
/**
* Get the data for the specified format from the {@link DataTransfer} object.
*
* @param format the format
* @return the data for the specified format
*/
public String getData(String format) {
DataTransfer dt = getDataTransfer();
return getDataTransfer().getData(format);
}
/**
* Get the {@link DataTransfer} associated with the current drag event.
*
* @return the {@link DataTransfer} object
*/
public DataTransfer getDataTransfer() {
return getNativeEvent().getDataTransfer();
}
/**
* Set the data in the {@link DataTransfer} object for the specified format.
*
* @param format the format
* @param data the data to associate with the format
*/
public void setData(String format, String data) {
getDataTransfer().setData(format, data);
}
}