org.gwt.dynamic.common.client.widgets.WrapPanel.java Source code

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Here is the source code for org.gwt.dynamic.common.client.widgets.WrapPanel.java

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/*
 * Copyright 2014 Maxim Dominichenko
 * 
 * Licensed under The MIT License (MIT) (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 * 
 * https://github.com/domax/gwt-dynamic-plugins/blob/master/LICENSE
 * 
 * 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 org.gwt.dynamic.common.client.widgets;

import java.util.HashSet;
import java.util.Set;

import com.google.gwt.core.client.impl.Disposable;
import com.google.gwt.core.client.impl.Impl;
import com.google.gwt.dom.client.Element;
import com.google.gwt.event.logical.shared.CloseEvent;
import com.google.gwt.event.logical.shared.CloseHandler;
import com.google.gwt.user.client.Window;
import com.google.gwt.user.client.ui.AttachDetachException;
import com.google.gwt.user.client.ui.ComplexPanel;
import com.google.gwt.user.client.ui.Widget;

public class WrapPanel extends ComplexPanel {

    private static Set<Widget> widgetsToDetach = new HashSet<Widget>();
    private static final AttachDetachException.Command maybeDetachCommand = new AttachDetachException.Command() {
        @Override
        public void execute(Widget w) {
            if (w.isAttached())
                ((WrapPanel) w).onDetach();
        }
    };

    public static WrapPanel wrap(Element element) {
        if (widgetsToDetach == null) {
            widgetsToDetach = new HashSet<Widget>();
            hookWindowClosing();
        }
        WrapPanel panel = new WrapPanel(element);
        panel.onAttach();
        detachOnWindowClose(panel);
        return panel;
    }

    public static void detachNow(WrapPanel panel) {
        assert widgetsToDetach.contains(panel) : "detachNow() called on a panel not currently in the detach list";
        try {
            panel.onDetach();
        } finally {
            widgetsToDetach.remove(panel);
        }
    }

    public static void detachOnWindowClose(WrapPanel panel) {
        assert !widgetsToDetach.contains(panel) : "detachOnUnload() called twice for the same panel";
        widgetsToDetach.add(panel);
    }

    private static void hookWindowClosing() {
        Impl.scheduleDispose(new Disposable() {
            @Override
            public void dispose() {
                detachWidgets();
            }
        });
        // Catch the window closing event.
        Window.addCloseHandler(new CloseHandler<Window>() {
            @Override
            public void onClose(CloseEvent<Window> closeEvent) {
                detachWidgets();
            }
        });
    }

    private static void detachWidgets() {
        // When the window is closing, detach all widgets that need to be
        // cleaned up. This will cause all of their event listeners
        // to be unhooked, which will avoid potential memory leaks.
        try {
            AttachDetachException.tryCommand(widgetsToDetach, maybeDetachCommand);
        } finally {
            widgetsToDetach.clear();
        }
    }

    private WrapPanel(Element element) {
        setElement(element);
    }

    @Override
    public void add(Widget widget) {
        add(widget, (Element) getElement());
    }
}