com.google.gwt.sample.mobilewebapp.client.ui.WindowBasedOrientationHelper.java Source code

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Here is the source code for com.google.gwt.sample.mobilewebapp.client.ui.WindowBasedOrientationHelper.java

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/*
 * 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.sample.mobilewebapp.client.ui;

import com.google.gwt.event.logical.shared.AttachEvent;
import com.google.gwt.event.logical.shared.HasAttachHandlers;
import com.google.gwt.event.logical.shared.ResizeEvent;
import com.google.gwt.event.logical.shared.ResizeHandler;
import com.google.gwt.user.client.Command;
import com.google.gwt.user.client.Window;
import com.google.web.bindery.event.shared.HandlerRegistration;

import java.util.HashSet;

/**
 * OrientationHelper implementation that works by by monitoring window size
 * changes, and so works on both mobile devices and desktop browsers.
 * <p>
 * Expected to be used as an app-wide singleton.
 */
public class WindowBasedOrientationHelper implements OrientationHelper {
    private class CommandSet implements AttachEvent.Handler, HandlerRegistration {
        final Command portraitCommand;
        final Command landscapeCommand;
        final HandlerRegistration attachEventReg;

        boolean active;

        CommandSet(HasAttachHandlers widget, Command portrait, Command landscape) {
            this.portraitCommand = portrait;
            this.landscapeCommand = landscape;

            attachEventReg = widget.addAttachHandler(this);
            active = widget.isAttached();
        }

        @Override
        public void onAttachOrDetach(AttachEvent event) {
            active = event.isAttached();
            fire();
        }

        @Override
        public void removeHandler() {
            commandSets.remove(this);
            attachEventReg.removeHandler();
        }

        void fire() {
            if (active) {
                if (isPortrait) {
                    portraitCommand.execute();
                } else {
                    landscapeCommand.execute();
                }
            }
        }
    }

    private static boolean calculateIsPortrait() {
        return Window.getClientHeight() > Window.getClientWidth();
    }

    private boolean isPortrait;
    private HandlerRegistration windowResizeReg;
    private HashSet<CommandSet> commandSets = new HashSet<CommandSet>();

    public WindowBasedOrientationHelper() {
        isPortrait = calculateIsPortrait();
        windowResizeReg = Window.addResizeHandler(new ResizeHandler() {
            public void onResize(ResizeEvent event) {
                update();
            }
        });
    }

    @Override
    public boolean isPortrait() {
        assertLive();
        return isPortrait;
    }

    @Override
    public HandlerRegistration setCommands(HasAttachHandlers widget, Command forPortrait, Command forLandscape) {
        assertLive();
        CommandSet commandSet = new CommandSet(widget, forPortrait, forLandscape);
        commandSets.add(commandSet);
        commandSet.fire();
        return commandSet;
    }

    public void stop() {
        assertLive();
        windowResizeReg.removeHandler();
        windowResizeReg = null;

        for (CommandSet commandSet : commandSets) {
            commandSet.attachEventReg.removeHandler();
        }
        commandSets = null;
    }

    private void assertLive() {
        assert windowResizeReg != null : "Cannot do this after stop() is called";
    }

    private void update() {
        boolean was = isPortrait;
        isPortrait = calculateIsPortrait();
        if (was != isPortrait) {
            for (CommandSet helper : commandSets) {
                helper.fire();
            }
        }
    }
}