// Copyright (C) 2009 The Android Open Source Project
//
// 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.gwtexpui.user.client;
import com.google.gwt.user.client.ui.Composite;
import com.google.gwt.user.client.ui.Widget;
/**
* Widget to display within a {@link ViewSite}.
*<p>
* Implementations must override {@code protected void onLoad()} and
* arrange for {@link #display()} to be invoked once the DOM within the view is
* consistent for presentation to the user. Typically this means that the
* subclass can start RPCs within {@code onLoad()} and then invoke
* {@code display()} from within the AsyncCallback's
* {@code onSuccess(Object)} method.
*/
public abstract class View extends Composite {
ViewSite<? extends View> site;
@Override
protected void onUnload() {
site = null;
super.onUnload();
}
/** true if this is the current view of its parent view site */
public final boolean isCurrentView() {
Widget p = getParent();
while (p != null) {
if (p instanceof ViewSite<?>) {
return ((ViewSite<?>) p).getView() == this;
}
p = p.getParent();
}
return false;
}
/** Replace the current view in the parent ViewSite with this view. */
public final void display() {
if (site != null) {
site.swap(this);
}
}
}