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// 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.FlowPanel;
import com.google.gwt.user.client.ui.SimplePanel;
/**
* Hosts a single {@link View}.
*
* <p>View instances are attached inside of an invisible DOM node, permitting their {@code onLoad()}
* method to be invoked and to update the DOM prior to the elements being made visible in the UI.
*
* <p>Complaint View instances must invoke {@link View#display()} once the DOM is ready for
* presentation.
*/
public class ViewSite<V extends View> extends Composite {
private final FlowPanel main;
private SimplePanel current;
private SimplePanel next;
public ViewSite() {
main = new FlowPanel();
initWidget(main);
}
/** Get the current view; null if there is no view being displayed. */
@SuppressWarnings("unchecked")
public V getView() {
return current != null ? (V) current.getWidget() : null;
}
/**
* Set the next view to display.
*
* <p>The view will be attached to the DOM tree within a hidden container, permitting its {@code
* onLoad()} method to execute and update the DOM without the user seeing the result.
*
* @param view the next view to display.
*/
public void setView(V view) {
if (next != null) {
main.remove(next);
}
view.site = this;
next = new SimplePanel();
next.setVisible(false);
main.add(next);
next.add(view);
}
/**
* Invoked after the view becomes the current view and has been made visible.
*
* @param view the view being displayed.
*/
protected void onShowView(V view) {}
@SuppressWarnings("unchecked")
final void swap(View v) {
if (next != null && next.getWidget() == v) {
if (current != null) {
main.remove(current);
}
current = next;
next = null;
current.setVisible(true);
onShowView((V) v);
}
}
}
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