问如何通过中心裁剪和宽/高来适配Live墙纸中的视频？

EN

    private fun initExoMediaPlayer(): SimpleExoPlayer {
        val videoTrackSelectionFactory = AdaptiveTrackSelection.Factory(bandwidthMeter)
        val trackSelector = DefaultTrackSelector(videoTrackSelectionFactory)
        val player = ExoPlayerFactory.newSimpleInstance(this@MovieLiveWallpaperService,
                trackSelector)
        player.playWhenReady = true
        player.repeatMode = Player.REPEAT_MODE_ONE
        player.volume = 0f
        if (mode == Mode.CENTER_CROP) {
            player.videoScalingMode = C.VIDEO_SCALING_MODE_SCALE_TO_FIT_WITH_CROPPING
        } else {
            player.videoScalingMode = C.VIDEO_SCALING_MODE_SCALE_TO_FIT
        }
        if (mode == Mode.FIT_CENTER) {
            player.addVideoListener(this)
        }
        return player
    }

    override fun onSurfaceCreated(holder: SurfaceHolder) {
        super.onSurfaceCreated(holder)
        if (mode == Mode.FIT_CENTER) {
            // We need to somehow wrap the surface or set some scale factor on exo player here.
            // Most likely this will require creating a SurfaceTexture and attaching it to an
            // OpenGL context. Then for each frame, writing it to the original surface but with
            // an offset
            exoMediaPlayer.setVideoSurface(holder.surface)
        } else {
            exoMediaPlayer.setVideoSurfaceHolder(holder)
        }

        val videoUri = RawResourceDataSource.buildRawResourceUri(R.raw.small)
        val dataSourceFactory = DataSource.Factory { RawResourceDataSource(context) }
        val mediaSourceFactory = ExtractorMediaSource.Factory(dataSourceFactory)
        exoMediaPlayer.prepare(mediaSourceFactory.createMediaSource(videoUri))
    }

public class TextureVideoView extends TextureView implements TextureView.SurfaceTextureListener {

    // Indicate if logging is on
    public static final boolean LOG_ON = true;

    // Log tag
    private static final String TAG = TextureVideoView.class.getName();

    private MediaPlayer mMediaPlayer;

    private float mVideoHeight;
    private float mVideoWidth;

    private boolean mIsDataSourceSet;
    private boolean mIsViewAvailable;
    private boolean mIsVideoPrepared;
    private boolean mIsPlayCalled;

    private ScaleType mScaleType;
    private State mState;

    public enum ScaleType {
        CENTER_CROP, TOP, BOTTOM
    }

    public enum State {
        UNINITIALIZED, PLAY, STOP, PAUSE, END
    }

    public TextureVideoView(Context context) {
        super(context);
        initView();
    }

    public TextureVideoView(Context context, AttributeSet attrs) {
        super(context, attrs);
        initView();
    }

    public TextureVideoView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        initView();
    }

    private void initView() {
        initPlayer();
        setScaleType(ScaleType.CENTER_CROP);
        setSurfaceTextureListener(this);
    }

    public void setScaleType(ScaleType scaleType) {
        mScaleType = scaleType;
    }

    private void updateTextureViewSize() {
        float viewWidth = getWidth();
        float viewHeight = getHeight();

        float scaleX = 1.0f;
        float scaleY = 1.0f;

        if (mVideoWidth > viewWidth && mVideoHeight > viewHeight) {
            scaleX = mVideoWidth / viewWidth;
            scaleY = mVideoHeight / viewHeight;
        } else if (mVideoWidth < viewWidth && mVideoHeight < viewHeight) {
            scaleY = viewWidth / mVideoWidth;
            scaleX = viewHeight / mVideoHeight;
        } else if (viewWidth > mVideoWidth) {
            scaleY = (viewWidth / mVideoWidth) / (viewHeight / mVideoHeight);
        } else if (viewHeight > mVideoHeight) {
            scaleX = (viewHeight / mVideoHeight) / (viewWidth / mVideoWidth);
        }

        // Calculate pivot points, in our case crop from center
        int pivotPointX;
        int pivotPointY;

        switch (mScaleType) {
            case TOP:
                pivotPointX = 0;
                pivotPointY = 0;
                break;
            case BOTTOM:
                pivotPointX = (int) (viewWidth);
                pivotPointY = (int) (viewHeight);
                break;
            case CENTER_CROP:
                pivotPointX = (int) (viewWidth / 2);
                pivotPointY = (int) (viewHeight / 2);
                break;
            default:
                pivotPointX = (int) (viewWidth / 2);
                pivotPointY = (int) (viewHeight / 2);
                break;
        }

        Matrix matrix = new Matrix();
        matrix.setScale(scaleX, scaleY, pivotPointX, pivotPointY);

        setTransform(matrix);
    }

    private void initPlayer() {
        if (mMediaPlayer == null) {
            mMediaPlayer = new MediaPlayer();
        } else {
            mMediaPlayer.reset();
        }
        mIsVideoPrepared = false;
        mIsPlayCalled = false;
        mState = State.UNINITIALIZED;
    }

    /**
     * @see MediaPlayer#setDataSource(String)
     */
    public void setDataSource(String path) {
        initPlayer();

        try {
            mMediaPlayer.setDataSource(path);
            mIsDataSourceSet = true;
            prepare();
        } catch (IOException e) {
            Log.d(TAG, e.getMessage());
        }
    }

    /**
     * @see MediaPlayer#setDataSource(Context, Uri)
     */
    public void setDataSource(Context context, Uri uri) {
        initPlayer();

        try {
            mMediaPlayer.setDataSource(context, uri);
            mIsDataSourceSet = true;
            prepare();
        } catch (IOException e) {
            Log.d(TAG, e.getMessage());
        }
    }

    /**
     * @see MediaPlayer#setDataSource(java.io.FileDescriptor)
     */
    public void setDataSource(AssetFileDescriptor afd) {
        initPlayer();

        try {
            long startOffset = afd.getStartOffset();
            long length = afd.getLength();
            mMediaPlayer.setDataSource(afd.getFileDescriptor(), startOffset, length);
            mIsDataSourceSet = true;
            prepare();
        } catch (IOException e) {
            Log.d(TAG, e.getMessage());
        }
    }

    private void prepare() {
        try {
            mMediaPlayer.setOnVideoSizeChangedListener(
                    new MediaPlayer.OnVideoSizeChangedListener() {
                        @Override
                        public void onVideoSizeChanged(MediaPlayer mp, int width, int height) {
                            mVideoWidth = width;
                            mVideoHeight = height;
                            updateTextureViewSize();
                        }
                    }
            );
            mMediaPlayer.setOnCompletionListener(new MediaPlayer.OnCompletionListener() {
                @Override
                public void onCompletion(MediaPlayer mp) {
                    mState = State.END;
                    log("Video has ended.");

                    if (mListener != null) {
                        mListener.onVideoEnd();
                    }
                }
            });

            // don't forget to call MediaPlayer.prepareAsync() method when you use constructor for
            // creating MediaPlayer
            mMediaPlayer.prepareAsync();

            // Play video when the media source is ready for playback.
            mMediaPlayer.setOnPreparedListener(new MediaPlayer.OnPreparedListener() {
                @Override
                public void onPrepared(MediaPlayer mediaPlayer) {
                    mIsVideoPrepared = true;
                    if (mIsPlayCalled && mIsViewAvailable) {
                        log("Player is prepared and play() was called.");
                        play();
                    }

                    if (mListener != null) {
                        mListener.onVideoPrepared();
                    }
                }
            });

        } catch (IllegalArgumentException e) {
            Log.d(TAG, e.getMessage());
        } catch (SecurityException e) {
            Log.d(TAG, e.getMessage());
        } catch (IllegalStateException e) {
            Log.d(TAG, e.toString());
        }
    }

    /**
     * Play or resume video. Video will be played as soon as view is available and media player is
     * prepared.
     *
     * If video is stopped or ended and play() method was called, video will start over.
     */
    public void play() {
        if (!mIsDataSourceSet) {
            log("play() was called but data source was not set.");
            return;
        }

        mIsPlayCalled = true;

        if (!mIsVideoPrepared) {
            log("play() was called but video is not prepared yet, waiting.");
            return;
        }

        if (!mIsViewAvailable) {
            log("play() was called but view is not available yet, waiting.");
            return;
        }

        if (mState == State.PLAY) {
            log("play() was called but video is already playing.");
            return;
        }

        if (mState == State.PAUSE) {
            log("play() was called but video is paused, resuming.");
            mState = State.PLAY;
            mMediaPlayer.start();
            return;
        }

        if (mState == State.END || mState == State.STOP) {
            log("play() was called but video already ended, starting over.");
            mState = State.PLAY;
            mMediaPlayer.seekTo(0);
            mMediaPlayer.start();
            return;
        }

        mState = State.PLAY;
        mMediaPlayer.start();
    }

    /**
     * Pause video. If video is already paused, stopped or ended nothing will happen.
     */
    public void pause() {
        if (mState == State.PAUSE) {
            log("pause() was called but video already paused.");
            return;
        }

        if (mState == State.STOP) {
            log("pause() was called but video already stopped.");
            return;
        }

        if (mState == State.END) {
            log("pause() was called but video already ended.");
            return;
        }

        mState = State.PAUSE;
        if (mMediaPlayer.isPlaying()) {
            mMediaPlayer.pause();
        }
    }

    /**
     * Stop video (pause and seek to beginning). If video is already stopped or ended nothing will
     * happen.
     */
    public void stop() {
        if (mState == State.STOP) {
            log("stop() was called but video already stopped.");
            return;
        }

        if (mState == State.END) {
            log("stop() was called but video already ended.");
            return;
        }

        mState = State.STOP;
        if (mMediaPlayer.isPlaying()) {
            mMediaPlayer.pause();
            mMediaPlayer.seekTo(0);
        }
    }

    /**
     * @see MediaPlayer#setLooping(boolean)
     */
    public void setLooping(boolean looping) {
        mMediaPlayer.setLooping(looping);
    }

    /**
     * @see MediaPlayer#seekTo(int)
     */
    public void seekTo(int milliseconds) {
        mMediaPlayer.seekTo(milliseconds);
    }

    /**
     * @see MediaPlayer#getDuration()
     */
    public int getDuration() {
        return mMediaPlayer.getDuration();
    }

    static void log(String message) {
        if (LOG_ON) {
            Log.d(TAG, message);
        }
    }

    private MediaPlayerListener mListener;

    /**
     * Listener trigger 'onVideoPrepared' and `onVideoEnd` events
     */
    public void setListener(MediaPlayerListener listener) {
        mListener = listener;
    }

    public interface MediaPlayerListener {

        public void onVideoPrepared();

        public void onVideoEnd();
    }

    @Override
    public void onSurfaceTextureAvailable(SurfaceTexture surfaceTexture, int width, int height) {
        Surface surface = new Surface(surfaceTexture);
        mMediaPlayer.setSurface(surface);
        mIsViewAvailable = true;
        if (mIsDataSourceSet && mIsPlayCalled && mIsVideoPrepared) {
            log("View is available and play() was called.");
            play();
        }
    }

    @Override
    public void onSurfaceTextureSizeChanged(SurfaceTexture surface, int width, int height) {

    }

    @Override
    public boolean onSurfaceTextureDestroyed(SurfaceTexture surface) {
        return false;
    }

    @Override
    public void onSurfaceTextureUpdated(SurfaceTexture surface) {

    }
}

public class MainActivity extends AppCompatActivity implements View.OnClickListener,
        ActionBar.OnNavigationListener {

    // Video file url
    private static final String FILE_URL = "http://techslides.com/demos/sample-videos/small.mp4";
    private TextureVideoView mTextureVideoView;

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

        initView();
        initActionBar();

        if (!isWIFIOn(getBaseContext())) {
            Toast.makeText(getBaseContext(), "You need internet connection to stream video",
                    Toast.LENGTH_LONG).show();
        }
    }

    private void initActionBar() {
        ActionBar actionBar = getSupportActionBar();
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_LIST);
        actionBar.setDisplayShowTitleEnabled(false);

        SpinnerAdapter mSpinnerAdapter = ArrayAdapter.createFromResource(this, R.array.action_list,
                android.R.layout.simple_spinner_dropdown_item);
        actionBar.setListNavigationCallbacks(mSpinnerAdapter, this);
    }

    private void initView() {
        mTextureVideoView = (TextureVideoView) findViewById(R.id.cropTextureView);

        findViewById(R.id.btnPlay).setOnClickListener(this);
        findViewById(R.id.btnPause).setOnClickListener(this);
        findViewById(R.id.btnStop).setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.btnPlay:
                mTextureVideoView.play();
                break;
            case R.id.btnPause:
                mTextureVideoView.pause();
                break;
            case R.id.btnStop:
                mTextureVideoView.stop();
                break;
        }
    }

    final int indexCropCenter = 0;
    final int indexCropTop = 1;
    final int indexCropBottom = 2;

    @Override
    public boolean onNavigationItemSelected(int itemPosition, long itemId) {
        switch (itemPosition) {
            case indexCropCenter:
                mTextureVideoView.stop();
                mTextureVideoView.setScaleType(TextureVideoView.ScaleType.CENTER_CROP);
                mTextureVideoView.setDataSource(FILE_URL);
                mTextureVideoView.play();
                break;
            case indexCropTop:
                mTextureVideoView.stop();
                mTextureVideoView.setScaleType(TextureVideoView.ScaleType.TOP);
                mTextureVideoView.setDataSource(FILE_URL);
                mTextureVideoView.play();
                break;
            case indexCropBottom:
                mTextureVideoView.stop();
                mTextureVideoView.setScaleType(TextureVideoView.ScaleType.BOTTOM);
                mTextureVideoView.setDataSource(FILE_URL);
                mTextureVideoView.play();
                break;
        }
        return true;
    }

    public static boolean isWIFIOn(Context context) {
        ConnectivityManager connMgr =
                (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo networkInfo = connMgr.getNetworkInfo(ConnectivityManager.TYPE_WIFI);

        return (networkInfo != null && networkInfo.isConnected());
    }
}

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

    <com.example.videocropdemo.crop.TextureVideoView
        android:id="@+id/cropTextureView"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:layout_centerInParent="true" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_margin="16dp"
        android:orientation="horizontal">

        <Button
            android:id="@+id/btnPlay"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Play" />

        <Button
            android:id="@+id/btnPause"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Pause" />

        <Button
            android:id="@+id/btnStop"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Stop" />
    </LinearLayout>
</RelativeLayout>

public class GLWallpaperService extends WallpaperService {
...

    class GLWallpaperEngine extends Engine {
...

        private class GLWallpaperSurfaceView extends GLSurfaceView {
            @SuppressWarnings("unused")
            private static final String TAG = "GLWallpaperSurface";

            public GLWallpaperSurfaceView(Context context) {
                super(context);
            }

            /**
             * This is a hack. Because Android Live Wallpaper only has a Surface.
             * So we create a GLSurfaceView, and when drawing to its Surface,
             * we replace it with WallpaperEngine's Surface.
             */
            @Override
            public SurfaceHolder getHolder() {
                return getSurfaceHolder();
            }

            void onDestroy() {
                super.onDetachedFromWindow();
            }
        }