使用媒体投影，屏幕记录是黑色的

Question

我试图使用MediaProjection API记录屏幕，但我似乎总是只得到一个黑色视频(整个视频长度显示黑色)，我对为什么一无所知。我在初始化MediaProjectionManager后调用startRecording()，然后调用releaseEncoders()停止录制。下面是我的代码:

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_screen_record);
    mMediaProjectionManager = (MediaProjectionManager) getSystemService(
            android.content.Context.MEDIA_PROJECTION_SERVICE);
    ToggleButton rec = (ToggleButton) findViewById(R.id.tggl);
    String[] perms = {"android.permission.WRITE_EXTERNAL_STORAGE"};
    if (!isStorageWritable()) {
        // We don't have permission so prompt the user
        requestPermissions(
                perms,
                REQUEST_EXTERNAL_STORAGE
        );
    }
    rec.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            if (((ToggleButton) view).isChecked()) {
                if (isStorageWritable()) {
                    Intent permissionIntent = mMediaProjectionManager.createScreenCaptureIntent();
                    startActivityForResult(permissionIntent, REQUEST_CODE_CAPTURE_PERM);
                }
            } else
                releaseEncoders();
        }
    });
}
private boolean isStorageWritable(){
    int permission = ActivityCompat.checkSelfPermission(this, "android.permission.WRITE_EXTERNAL_STORAGE");
    if (permission == PackageManager.PERMISSION_GRANTED)
        return true;
    else
        return false;
}
private Runnable mDrainEncoderRunnable = new Runnable() {
    @Override
    public void run() {
        drainEncoder();
    }
};
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (REQUEST_CODE_CAPTURE_PERM == requestCode) {
        if (resultCode == RESULT_OK) {
            mMediaProjection = mMediaProjectionManager.getMediaProjection(resultCode, data);
            startRecording(); // defined below
        } else {
            // user did not grant permissions
        }
    }
}
private void startRecording() {
    DisplayManager dm = (DisplayManager)getSystemService(Context.DISPLAY_SERVICE);
    Display defaultDisplay = dm.getDisplay(Display.DEFAULT_DISPLAY);
    if (defaultDisplay == null) {
        throw new RuntimeException("No display found.");
    }
    prepareVideoEncoder();
    try {
        mMuxer = new MediaMuxer(Environment.getExternalStorageDirectory() + "/video.mp4", MediaMuxer.OutputFormat.MUXER_OUTPUT_MPEG_4);
    } catch (IOException ioe) {
        throw new RuntimeException("MediaMuxer creation failed", ioe);
    }
    // Get the display size and density.
    DisplayMetrics metrics = getResources().getDisplayMetrics();
    int screenWidth = metrics.widthPixels;
    int screenHeight = metrics.heightPixels;
    int screenDensity = metrics.densityDpi;
    // Start the video input.
    mMediaProjection.createVirtualDisplay("Recording Display", screenWidth,
            screenHeight, screenDensity, 0 /* flags */, mInputSurface,
            null /* callback */, null /* handler */);
    // Start the encoders
    drainEncoder();
}
private void prepareVideoEncoder() {
    mVideoBufferInfo = new MediaCodec.BufferInfo();
    MediaFormat format = MediaFormat.createVideoFormat(VIDEO_MIME_TYPE, VIDEO_WIDTH, VIDEO_HEIGHT);
    int frameRate = 30; // 30 fps
    // Set some required properties. The media codec may fail if these aren't defined.
    format.setInteger(MediaFormat.KEY_COLOR_FORMAT,
            MediaCodecInfo.CodecCapabilities.COLOR_FormatSurface);
    format.setInteger(MediaFormat.KEY_BIT_RATE, 6000000); // 6Mbps
    format.setInteger(MediaFormat.KEY_FRAME_RATE, frameRate);
    format.setInteger(MediaFormat.KEY_CAPTURE_RATE, frameRate);
    format.setInteger(MediaFormat.KEY_REPEAT_PREVIOUS_FRAME_AFTER, 1000000 / frameRate);
    format.setInteger(MediaFormat.KEY_CHANNEL_COUNT, 1);
    format.setInteger(MediaFormat.KEY_I_FRAME_INTERVAL, 1); // 1 seconds between I-frames
    // Create a MediaCodec encoder and configure it. Get a Surface we can use for recording into.
    try {
        mVideoEncoder = MediaCodec.createEncoderByType(VIDEO_MIME_TYPE);
        mVideoEncoder.configure(format, null, null, MediaCodec.CONFIGURE_FLAG_ENCODE);
        mInputSurface = mVideoEncoder.createInputSurface();
        mVideoEncoder.start();
    } catch (IOException e) {
        releaseEncoders();
    }
}
private boolean drainEncoder() {
    mDrainHandler.removeCallbacks(mDrainEncoderRunnable);
    while (true) {
        int bufferIndex = mVideoEncoder.dequeueOutputBuffer(mVideoBufferInfo, 0);
        if (bufferIndex == MediaCodec.INFO_TRY_AGAIN_LATER) {
            // nothing available yet
            break;
        } else if (bufferIndex == MediaCodec.INFO_OUTPUT_FORMAT_CHANGED) {
            // should happen before receiving buffers, and should only happen once
            if (mTrackIndex >= 0) {
                throw new RuntimeException("format changed twice");
            }
            mTrackIndex = mMuxer.addTrack(mVideoEncoder.getOutputFormat());
            if (!mMuxerStarted && mTrackIndex >= 0) {
                mMuxer.start();
                mMuxerStarted = true;
            }
        } else if (bufferIndex < 0) {
            // not sure what's going on, ignore it
        } else {
            ByteBuffer encodedData = mVideoEncoder.getOutputBuffer(bufferIndex);
            if (encodedData == null) {
                throw new RuntimeException("couldn't fetch buffer at index " + bufferIndex);
            }
            if ((mVideoBufferInfo.flags & MediaCodec.BUFFER_FLAG_CODEC_CONFIG) != 0) {
                mVideoBufferInfo.size = 0;
            }
            if (mVideoBufferInfo.size != 0) {
                if (mMuxerStarted) {
                    encodedData.position(mVideoBufferInfo.offset);
                    encodedData.limit(mVideoBufferInfo.offset + mVideoBufferInfo.size);
                    mMuxer.writeSampleData(mTrackIndex, encodedData, mVideoBufferInfo);
                } else {
                    // muxer not started
                }
            }
            mVideoEncoder.releaseOutputBuffer(bufferIndex, false);
            if ((mVideoBufferInfo.flags & MediaCodec.BUFFER_FLAG_END_OF_STREAM) != 0) {
                break;
            }
        }
    }
    mDrainHandler.postDelayed(mDrainEncoderRunnable, 10);
    return false;
}
private void releaseEncoders() {
    mDrainHandler.removeCallbacks(mDrainEncoderRunnable);
    Toast.makeText(this, "Stopping recording", Toast.LENGTH_SHORT).show();
    if (mMuxer != null) {
        if (mMuxerStarted) {
            mMuxer.stop();
        }
        mMuxer.release();
        mMuxer = null;
        mMuxerStarted = false;
    }
    if (mVideoEncoder != null) {
        mVideoEncoder.stop();
        mVideoEncoder.release();
        mVideoEncoder = null;
    }
    if (mInputSurface != null) {
        mInputSurface.release();
        mInputSurface = null;
    }
    if (mMediaProjection != null) {
        mMediaProjection.stop();
        mMediaProjection = null;
    }
    mVideoBufferInfo = null;
    mDrainEncoderRunnable = null;
    mTrackIndex = -1;
}

Answer 1

这就解决了我的问题。

private static final String TAG = "MainActivity";
private static final int REQUEST_CODE = 1000;
private int mScreenDensity;
private MediaProjectionManager mProjectionManager;
private static final int DISPLAY_WIDTH = 720;
private static final int DISPLAY_HEIGHT = 1280;
private MediaProjection mMediaProjection;
private VirtualDisplay mVirtualDisplay;
private MediaProjectionCallback mMediaProjectionCallback;
private ToggleButton mToggleButton;
private MediaRecorder mMediaRecorder;
private static final SparseIntArray ORIENTATIONS = new SparseIntArray();
private static final int REQUEST_PERMISSIONS = 10;
static {
    ORIENTATIONS.append(Surface.ROTATION_0, 90);
    ORIENTATIONS.append(Surface.ROTATION_90, 0);
    ORIENTATIONS.append(Surface.ROTATION_180, 270);
    ORIENTATIONS.append(Surface.ROTATION_270, 180);
}
@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode != REQUEST_CODE) {
        Log.e(TAG, "Unknown request code: " + requestCode);
        return;
    }
    if (resultCode != RESULT_OK) {
        Toast.makeText(this,
                "Screen Cast Permission Denied", Toast.LENGTH_SHORT).show();
        mToggleButton.setChecked(false);
        return;
    }
    mMediaProjectionCallback = new MediaProjectionCallback();
    mMediaProjection = mProjectionManager.getMediaProjection(resultCode, data);
    mMediaProjection.registerCallback(mMediaProjectionCallback, null);
    mVirtualDisplay = createVirtualDisplay();
    mMediaRecorder.start();
}
public void onToggleScreenShare(View view) {
    if (((ToggleButton) view).isChecked()) {
        initRecorder();
        shareScreen();
    } else {
        mMediaRecorder.stop();
        mMediaRecorder.reset();
        Log.v(TAG, "Stopping Recording");
        stopScreenSharing();
    }
}
private void shareScreen() {
    if (mMediaProjection == null) {
        startActivityForResult(mProjectionManager.createScreenCaptureIntent(), REQUEST_CODE);
        return;
    }
    mVirtualDisplay = createVirtualDisplay();
    mMediaRecorder.start();
}
private VirtualDisplay createVirtualDisplay() {
    return mMediaProjection.createVirtualDisplay("MainActivity",
            DISPLAY_WIDTH, DISPLAY_HEIGHT, mScreenDensity,
            DisplayManager.VIRTUAL_DISPLAY_FLAG_AUTO_MIRROR,
            mMediaRecorder.getSurface(), null /*Callbacks*/, null
            /*Handler*/);
}
private void initRecorder() {
    try {
        mMediaRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
        mMediaRecorder.setVideoSource(MediaRecorder.VideoSource.SURFACE);
        mMediaRecorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
        mMediaRecorder.setOutputFile(Environment
                .getExternalStoragePublicDirectory(Environment
                        .DIRECTORY_DOWNLOADS) + "/video.mp4");
        mMediaRecorder.setVideoSize(DISPLAY_WIDTH, DISPLAY_HEIGHT);
        mMediaRecorder.setVideoEncoder(MediaRecorder.VideoEncoder.H264);
        mMediaRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
        mMediaRecorder.setVideoEncodingBitRate(512 * 1000);
        mMediaRecorder.setVideoFrameRate(30);
        int rotation = getWindowManager().getDefaultDisplay().getRotation();
        int orientation = ORIENTATIONS.get(rotation + 90);
        mMediaRecorder.setOrientationHint(orientation);
        mMediaRecorder.prepare();
    } catch (IOException e) {
        e.printStackTrace();
    }
}
private class MediaProjectionCallback extends MediaProjection.Callback {
    @Override
    public void onStop() {
        if (mToggleButton.isChecked()) {
            mToggleButton.setChecked(false);
            mMediaRecorder.stop();
            mMediaRecorder.reset();
            Log.v(TAG, "Recording Stopped");
        }
        mMediaProjection = null;
        stopScreenSharing();
    }
}
private void stopScreenSharing() {
    if (mVirtualDisplay == null) {
        return;
    }
    mVirtualDisplay.release();
    //mMediaRecorder.release(); //If used: mMediaRecorder object cannot
    // be reused again
    destroyMediaProjection();
}
@Override
public void onDestroy() {
    super.onDestroy();
    destroyMediaProjection();
}
private void destroyMediaProjection() {
    if (mMediaProjection != null) {
        mMediaProjection.unregisterCallback(mMediaProjectionCallback);
        mMediaProjection.stop();
        mMediaProjection = null;
    }
    Log.i(TAG, "MediaProjection Stopped");
}

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