Android 录制MP4添加时间水印

要在 Android 上录制 MP4 并添加时间水印，你可以使用 MediaRecorder 和 Canvas 对象。下面是一个简单的示例代码：

public class MainActivity extends AppCompatActivity {

    private static final String TAG = "MainActivity";

    private MediaRecorder mediaRecorder;
    private SurfaceView surfaceView;
    private SurfaceHolder surfaceHolder;

    private boolean isRecording = false;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // 初始化 SurfaceView 和 SurfaceHolder
        surfaceView = findViewById(R.id.surface_view);
        surfaceHolder = surfaceView.getHolder();
        surfaceHolder.addCallback(new SurfaceHolder.Callback() {
            @Override
            public void surfaceCreated(SurfaceHolder holder) {
                // 初始化 MediaRecorder
                mediaRecorder = new MediaRecorder();
                mediaRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
                mediaRecorder.setVideoSource(MediaRecorder.VideoSource.SURFACE);
                mediaRecorder.setOutputFormat(MediaRecorder.OutputFormat.MPEG_4);
                mediaRecorder.setVideoEncodingBitRate(10000000);
                mediaRecorder.setVideoFrameRate(30);
                mediaRecorder.setVideoSize(1280, 720);
                mediaRecorder.setOutputFile(getOutputFile().getAbsolutePath());
                mediaRecorder.setOrientationHint(90);
                mediaRecorder.setVideoEncoder(MediaRecorder.VideoEncoder.H264);
                mediaRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AAC);

                try {
                    mediaRecorder.prepare();
                } catch (IOException e) {
                    Log.e(TAG, "prepare() failed: " + e.getMessage());
                }
            }

            @Override
            public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
            }

            @Override
            public void surfaceDestroyed(SurfaceHolder holder) {
                releaseMediaRecorder();
            }
        });
    }

    private File getOutputFile() {
        File dir = new File(Environment.getExternalStorageDirectory(), "MyVideo");
        if (!dir.exists()) {
            dir.mkdirs();
        }
        SimpleDateFormat dateFormat = new SimpleDateFormat("yyyyMMdd_HHmmss", Locale.getDefault());
        String currentTimeStamp = dateFormat.format(new Date());
        return new File(dir.getAbsolutePath() + File.separator + "VID_" + currentTimeStamp + ".mp4");
    }

    private void releaseMediaRecorder() {
        if (mediaRecorder != null) {
            try {
                mediaRecorder.stop();
                mediaRecorder.reset();
                mediaRecorder.release();
                mediaRecorder = null;
            } catch (Exception e) {
                Log.e(TAG, "releaseMediaRecorder() failed: " + e.getMessage());
            }
        }
    }

    private void startRecording() {
        mediaRecorder.start();
        isRecording = true;

        // 开始绘制时间水印
        new Thread(new Runnable() {
            @Override
            public void run() {
                Canvas canvas = surfaceHolder.lockCanvas();
                Paint paint = new Paint();
                paint.setColor(Color.RED);
                paint.setTextSize(60);
                while (isRecording) {
                    canvas.drawText(getCurrentTime(), 100, 100, paint);
                    surfaceHolder.unlockCanvasAndPost(canvas);
                    SystemClock.sleep(1000);
                }
            }
        }).start();
    }

    private void stopRecording() {
        isRecording = false;
        releaseMediaRecorder();
    }

    private String getCurrentTime() {
        SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss", Locale.getDefault());
        return dateFormat.format(new Date());
    }

    public void onRecordBtnClick(View view) {
        if (isRecording) {
            stopRecording();
            ((Button) view).setText("Record");
        } else {
            startRecording();
            ((Button) view).setText("Stop");
        }
    }
}

上面的代码中，我们首先使用 MediaRecorder 和 SurfaceHolder 来初始化录制器和 SurfaceView。然后，我们在 surfaceCreated() 方法中初始化了 MediaRecorder 并将其准备好。在录制开始时，我们使用 Canvas 对象绘制时间水印，并将其加入到 SurfaceView 中。在录制结束时，我们释放了 MediaRecorder 并停止了绘制水印的线程。

需要注意的是，为了在 Android 上录制视频，你需要在 AndroidManifest.xml 文件中添加以下权限：

<uses-permission android:name="android.permission.RECORD_AUDIO" />
<uses-permission android:name="android.permission.CAMERA" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

同时，你也需要在运行时请求这些权限。