我正在尝试使用MediaProjectionAPI 录制屏幕，但我似乎总是只得到一个黑色视频（整个视频长度显示为黑色），我对原因一无所知。我startRecording()在初始化MediaProjectionManager之后打电话，然后打电话releaseEncoders()停止录音。这是我的代码：
@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;
}