Android Screen Capturer.

webrtc/api/android/java/src/org/webrtc/ScreenCapturerAndroid.java

+/*
+ *  Copyright 2016 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+package org.webrtc;
+
+import android.annotation.TargetApi;
+import android.app.Activity;
+import android.content.Context;
+import android.content.Intent;
+import android.hardware.display.DisplayManager;
+import android.hardware.display.VirtualDisplay;
+import android.media.projection.MediaProjection;
+import android.media.projection.MediaProjectionManager;
+import android.view.Surface;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * An implementation of VideoCapturer to capture the screen content as a video stream.
+ * Capturing is done by {@code MediaProjection} on a {@code SurfaceTexture}. We interact with this
+ * {@code SurfaceTexture} using a {@code SurfaceTextureHelper}.
+ * The {@code SurfaceTextureHelper} is created by the native code and passed to this capturer in
+ * {@code VideoCapturer.initialize()}. On receiving a new frame, this capturer passes it
+ * as a texture to the native code via {@code CapturerObserver.onTextureFrameCaptured()}. This takes
+ * place on the HandlerThread of the given {@code SurfaceTextureHelper}. When done with each frame,
+ * the native code returns the buffer to the  {@code SurfaceTextureHelper} to be used for new
+ * frames. At any time, at most one frame is being processed.
+ */
+@TargetApi(21)
+public class ScreenCapturerAndroid implements
+    VideoCapturer, SurfaceTextureHelper.OnTextureFrameAvailableListener {
+
+  private static final int DISPLAY_FLAGS = DisplayManager.VIRTUAL_DISPLAY_FLAG_PUBLIC
+      | DisplayManager.VIRTUAL_DISPLAY_FLAG_PRESENTATION;
+  // DPI for VirtualDisplay, does not seem to matter for us.
+  private static final int VIRTUAL_DISPLAY_DPI = 400;
+
+  private final Intent mediaProjectionPermissionResultData;
+  private final MediaProjection.Callback mediaProjectionCallback;
+
+  private int width;
+  private int height;
+  private VirtualDisplay virtualDisplay;
+  private SurfaceTextureHelper surfaceTextureHelper;
+  private CapturerObserver capturerObserver;
+  private long numCapturedFrames = 0;
+  private MediaProjection mediaProjection;
+  private boolean isDisposed = false;
+  private MediaProjectionManager mediaProjectionManager;
+
+  /**
+   * Constructs a new Screen Capturer.
+   *
+   * @param mediaProjectionPermissionResultData the result data of MediaProjection permission
+   *     activity; the calling app must validate that result code is Activity.RESULT_OK before
+   *     calling this method.
+   * @param mediaProjectionCallback MediaProjection callback to implement application specific
+   *     logic in events such as when the user revokes a previously granted capture permission.
+  **/
+  public ScreenCapturerAndroid(
+      Intent mediaProjectionPermissionResultData,
+      MediaProjection.Callback mediaProjectionCallback) {
+    this.mediaProjectionPermissionResultData = mediaProjectionPermissionResultData;
+    this.mediaProjectionCallback = mediaProjectionCallback;
+  }
+
+  private void checkNotDisposed() {
+    if (isDisposed) {
+      throw new RuntimeException("capturer is disposed.");
+    }
+  }
+
+  @Override
+  public synchronized void initialize(
+      final SurfaceTextureHelper surfaceTextureHelper,
+      final Context applicationContext,
+      final VideoCapturer.CapturerObserver capturerObserver) {
+    checkNotDisposed();
+
+    if (capturerObserver == null) {
+      throw new RuntimeException("capturerObserver not set.");
+    }
+    this.capturerObserver = capturerObserver;
+
+    if (surfaceTextureHelper == null) {
+      throw new RuntimeException("surfaceTextureHelper not set.");
+    }
+    this.surfaceTextureHelper = surfaceTextureHelper;
+
+    mediaProjectionManager = (MediaProjectionManager)
+        applicationContext.getSystemService(Context.MEDIA_PROJECTION_SERVICE);
+  }
+
+  /**
+   * This method is not called by native code, neither by the java app. It can be removed later
+   * once it is removed from the VideoCapturer interface.
+   */
+  @Override
+  public List<CameraEnumerationAndroid.CaptureFormat> getSupportedFormats() {
+    return null;
+  }
+
+  @Override
+  public synchronized void startCapture(final int width, final int height,
+       final int ignoredFramerate) {
+    checkNotDisposed();
+
+    this.width = width;
+    this.height = height;
+
+    mediaProjection = mediaProjectionManager.getMediaProjection(
+        Activity.RESULT_OK, mediaProjectionPermissionResultData);
+
+    // Let MediaProjection callback use the SurfaceTextureHelper thread.
+    mediaProjection.registerCallback(mediaProjectionCallback, surfaceTextureHelper.getHandler());
+
+    createVirtualDisplay();
+    capturerObserver.onCapturerStarted(true);
+    surfaceTextureHelper.startListening(ScreenCapturerAndroid.this);
+  }
+
+  @Override
+  public synchronized void stopCapture() {
+    checkNotDisposed();
+    ThreadUtils.invokeAtFrontUninterruptibly(surfaceTextureHelper.getHandler(), new Runnable() {
+      @Override
+      public void run() {
+        surfaceTextureHelper.stopListening();
+        capturerObserver.onCapturerStopped();
+
+        if (virtualDisplay != null) {
+          virtualDisplay.release();
+          virtualDisplay = null;
+        }
+
+        if (mediaProjection != null) {
+          // Unregister the callback before stopping, otherwise the callback recursively
+          // calls this method.
+          mediaProjection.unregisterCallback(mediaProjectionCallback);
+          mediaProjection.stop();
+          mediaProjection = null;
+        }
+      }
+    });
+  }
+
+
+  @Override
+  public synchronized void dispose() {
+    isDisposed = true;
+  }
+
+  @Override
+  public synchronized void onOutputFormatRequest(
+      final int width, final int height, final int framerate) {
+    checkNotDisposed();
+    surfaceTextureHelper.getHandler().post(new Runnable() {
+      @Override
+      public void run() {
+        capturerObserver.onOutputFormatRequest(width, height, framerate);
+      }
+    });
+  }
+
+  /**
+   * Changes output video format. This method can be used to scale the output
+   * video, or to change orientation when the captured screen is rotated for example.
+   *
+   * @param width new output video width
+   * @param height new output video height
+   * @param ignoredFramerate ignored
+   */
+  @Override
+  public synchronized void changeCaptureFormat(
+      final int width, final int height, final int ignoredFramerate) {
+    checkNotDisposed();
+
+    this.width = width;
+    this.height = height;
+
+    if (virtualDisplay == null) {
+      // Capturer is stopped, the virtual display will be created in startCaptuer().
+      return;
+    }
+
+    // Create a new virtual display on the surfaceTextureHelper thread to avoid interference
+    // with frame processing, which happens on the same thread (we serialize events by running
+    // them on the same thread).
+    ThreadUtils.invokeAtFrontUninterruptibly(surfaceTextureHelper.getHandler(), new Runnable() {
+      @Override
+      public void run() {
+        virtualDisplay.release();
+        createVirtualDisplay();
+      }
+    });
+  }
+
+  private void createVirtualDisplay() {
+    surfaceTextureHelper.getSurfaceTexture().setDefaultBufferSize(width, height);
+    virtualDisplay = mediaProjection.createVirtualDisplay(
+        "WebRTC_ScreenCapture", width, height, VIRTUAL_DISPLAY_DPI,
+        DISPLAY_FLAGS, new Surface(surfaceTextureHelper.getSurfaceTexture()),
+        null /* callback */, null /* callback handler */);
+  }
+
+  // This is called on the internal looper thread of {@Code SurfaceTextureHelper}.
+  @Override
+  public void onTextureFrameAvailable(int oesTextureId, float[] transformMatrix, long timestampNs) {
+    numCapturedFrames++;
+    capturerObserver.onTextureFrameCaptured(width, height, oesTextureId, transformMatrix,
+        0 /* rotation */, timestampNs);
+  }
+
+  @Override
+  public boolean isScreencast() {
+    return true;
+  }
+
+  public long getNumCapturedFrames() {
+    return numCapturedFrames;
+  }
+}
+