https://source.android.com/ 
/*
 * Copyright (C) 2013 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 android.hardware.display;

import android.view.Display;
import android.view.Surface;


Represents a virtual display. The content of a virtual display is rendered to a Surface that you must provide to 
createVirtualDisplay(). 
 Because a virtual display renders to a surface provided by the application, it will be released automatically when the process terminates and all remaining windows on it will be forcibly removed. However, you should also explicitly call release when you're done with it. 


See Also:
/**
 * Represents a virtual display. The content of a virtual display is rendered to a
 * {@link android.view.Surface} that you must provide to {@link DisplayManager#createVirtualDisplay
 * createVirtualDisplay()}.
 * <p>
 * Because a virtual display renders to a surface provided by the application, it will be
 * released automatically when the process terminates and all remaining windows on it will
 * be forcibly removed.  However, you should also explicitly call {@link #release} when
 * you're done with it.
 * </p>
 *
 * @see DisplayManager#createVirtualDisplay
 */
public final class VirtualDisplay {
    private final DisplayManagerGlobal mGlobal;
    private final Display mDisplay;
    private IVirtualDisplayCallback mToken;
    private Surface mSurface;

    VirtualDisplay(DisplayManagerGlobal global, Display display,
            IVirtualDisplayCallback token, Surface surface) {
        mGlobal = global;
        mDisplay = display;
        mToken = token;
        mSurface = surface;
    }

    
Gets the virtual display.

/**
     * Gets the virtual display.
     */
    public Display getDisplay() {
        return mDisplay;
    }

    
Gets the surface that backs the virtual display.

/**
     * Gets the surface that backs the virtual display.
     */
    public Surface getSurface() {
        return mSurface;
    }

    
Sets the surface that backs the virtual display.


Detaching the surface that backs a virtual display has a similar effect to
turning off the screen.


It is still the caller's responsibility to destroy the surface after it has
been detached.



Params:
  • surface – The surface to set, or null to detach the surface from the virtual display.
/**
     * Sets the surface that backs the virtual display.
     * <p>
     * Detaching the surface that backs a virtual display has a similar effect to
     * turning off the screen.
     * </p><p>
     * It is still the caller's responsibility to destroy the surface after it has
     * been detached.
     * </p>
     *
     * @param surface The surface to set, or null to detach the surface from the virtual display.
     */
    public void setSurface(Surface surface) {
        if (mSurface != surface) {
            mGlobal.setVirtualDisplaySurface(mToken, surface);
            mSurface = surface;
        }
    }

    
Asks the virtual display to resize.


This is really just a convenience to allow applications using
virtual displays to adapt to changing conditions without having
to tear down and recreate the display.



/**
     * Asks the virtual display to resize.
     *<p>
     * This is really just a convenience to allow applications using
     * virtual displays to adapt to changing conditions without having
     * to tear down and recreate the display.
     * </p>
     */
    public void resize(int width, int height, int densityDpi) {
        mGlobal.resizeVirtualDisplay(mToken, width, height, densityDpi);
    }

    
Releases the virtual display and destroys its underlying surface.


All remaining windows on the virtual display will be forcibly removed
as part of releasing the virtual display.



/**
     * Releases the virtual display and destroys its underlying surface.
     * <p>
     * All remaining windows on the virtual display will be forcibly removed
     * as part of releasing the virtual display.
     * </p>
     */
    public void release() {
        if (mToken != null) {
            mGlobal.releaseVirtualDisplay(mToken);
            mToken = null;
        }
    }

    @Override
    public String toString() {
        return "VirtualDisplay{display=" + mDisplay + ", token=" + mToken
                + ", surface=" + mSurface + "}";
    }

    
Interface for receiving information about a VirtualDisplay's state changes. 
/**
     * Interface for receiving information about a {@link VirtualDisplay}'s state changes.
     */
    public static abstract class Callback {
        
Called when the virtual display video projection has been
paused by the system or when the surface has been detached
by the application by calling setSurface(null).
The surface will not receive any more buffers while paused.

/**
         * Called when the virtual display video projection has been
         * paused by the system or when the surface has been detached
         * by the application by calling setSurface(null).
         * The surface will not receive any more buffers while paused.
         */
         public void onPaused() { }

        
Called when the virtual display video projection has been
resumed after having been paused.

/**
         * Called when the virtual display video projection has been
         * resumed after having been paused.
         */
         public void onResumed() { }

        
Called when the virtual display video projection has been
stopped by the system.  It will no longer receive frames
and it will never be resumed.  It is still the responsibility
of the application to release() the virtual display.

/**
         * Called when the virtual display video projection has been
         * stopped by the system.  It will no longer receive frames
         * and it will never be resumed.  It is still the responsibility
         * of the application to release() the virtual display.
         */
        public void onStopped() { }
    }
}