生成安卓短视频的实现代码

生成安卓短视频的实现代码可以分为以下几个步骤：

1. 导入必要的依赖库：

dependencies {
    implementation 'com.google.android.material:material:1.2.0'
    implementation 'com.github.rtoshiro.mflibrary:mflibrary:1.0.0'
    implementation "com.googlecode.mp4parser:isoparser:1.1.22"
    implementation 'com.googlecode.mp4parser:muxer:1.1.2'
    implementation 'com.googlecode.mp4parser:splitter:1.1.2'
}

2. 创建一个视频录制的 Activity，并在布局文件中添加相机预览和录制按钮等控件：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

  <FrameLayout
      android:id="@+id/camera_preview"
      android:layout_width="match_parent"
      android:layout_height="match_parent" />

  <ImageButton
      android:id="@+id/btn_record"
      android:layout_width="80dp"
      android:layout_height="80dp"
      android:layout_centerInParent="true"
      android:src="@drawable/ic_camera_record"
      android:background="@drawable/selector_camera_record_button" />

</RelativeLayout>

3. 在 Activity 中实现相机预览和录制逻辑：

public class VideoRecorderActivity extends AppCompatActivity implements SurfaceHolder.Callback, Camera.PreviewCallback {

    private Camera mCamera;
    private SurfaceHolder mHolder;
    private VideoCapture mVideoCapture;
    private boolean mIsRecording;
    private long mStartTime;

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

        SurfaceView preview = findViewById(R.id.camera_preview);
        mHolder = preview.getHolder();
        mHolder.addCallback(this);

        ImageButton recordButton = findViewById(R.id.btn_record);
        recordButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (mIsRecording) {
                    stopRecording();
                } else {
                    startRecording();
                }
            }
        });
    }

    private void startRecording() {
        try {
            mVideoCapture = new VideoCapture.Builder()
                    .setVideoSize(640, 480)
                    .setVideoCodec(MediaRecorder.VideoEncoder.H264)
                    .setAudioCodec(MediaRecorder.AudioEncoder.AAC)
                    .setOutputFile(getVideoFile())
                    .build();

            mVideoCapture.prepare();
            mVideoCapture.start();
            mIsRecording = true;
            mStartTime = System.currentTimeMillis();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private void stopRecording() {
        try {
            mVideoCapture.stop();
            mVideoCapture.release();
            mIsRecording = false;
            long duration = System.currentTimeMillis() - mStartTime;
            Toast.makeText(this, "录制完成，时长：" + duration / 1000 + "秒", Toast.LENGTH_SHORT).show();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private String getVideoFile() {
        File dir = new File(Environment.getExternalStorageDirectory(), "video");
        if (!dir.exists()) {
            dir.mkdirs();
        }
        return new File(dir, "video.mp4").getAbsolutePath();
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        try {
            mCamera = Camera.open();
            mCamera.setPreviewDisplay(holder);
            mCamera.setPreviewCallback(this);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
        Camera.Parameters params = mCamera.getParameters();
        params.setPreviewSize(width, height);
        params.setFocusMode(Camera.Parameters.FOCUS_MODE_AUTO);
        mCamera.setParameters(params);
        mCamera.startPreview();
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        mCamera.setPreviewCallback(null);
        mCamera.stopPreview();
        mCamera.release();
        mCamera = null;
    }

    @Override
    public void onPreviewFrame(byte[] data, Camera camera) {
        if (mIsRecording) {
            mVideoCapture.writeVideoData(data);
        }
    }
}

4. 使用 Mp4Parser 库把录制的视频文件合并成一个短视频：

public class VideoMerger {

    public static String merge(List<String> videoPaths, String outputFilePath) throws IOException {
        Movie[] movies = new Movie[videoPaths.size()];
        for (int i = 0; i < videoPaths.size(); i++) {
            movies[i] = MovieCreator.build(videoPaths.get(i));
        }

        List<Track> videoTracks = new LinkedList<>();
        List<Track> audioTracks = new LinkedList<>();

        for (Movie movie : movies) {
            for (Track track : movie.getTracks()) {
                if (track.getHandler().equals("soun")) {
                    audioTracks.add(track);
                }
                if (track.getHandler().equals("vide")) {
                    videoTracks.add(track);
                }
            }
        }

        Movie result = new Movie();

        if (!audioTracks.isEmpty()) {
            result.addTrack(new AppendTrack(audioTracks.toArray(new Track[audioTracks.size()])));
        }
        if (!videoTracks.isEmpty()) {
            result.addTrack(new AppendTrack(videoTracks.toArray(new Track[videoTracks.size()])));
        }

        Container out = new DefaultMp4Builder().build(result);
        FileOutputStream fos = new FileOutputStream(outputFilePath);
        FileChannel fc = fos.getChannel();
        out.writeContainer(fc);
        fc.close();
        fos.close();

        return outputFilePath;
    }
}

以上就是生成安卓短视频的实现代码，需要注意的是，这只是一个简单的示例，并没有考虑到多个视频的拼接、视频编辑等复杂功能。