可以通过重写Activity的onBackPressed()方法，并调用hide()或setVisibility(View.GONE)方法来隐藏媒体播放器控制器。

以下是示例代码：

public class MainActivity extends AppCompatActivity {
    private VideoView mVideoView;
    private MediaController mMediaController;

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

        mVideoView = findViewById(R.id.videoView);
        mMediaController = new MediaController(this);
        mVideoView.setMediaController(mMediaController);

        // 设置视频文件路径
        String videoPath = "android.resource://" + getPackageName() + "/" + R.raw.video;
        mVideoView.setVideoPath(videoPath);

        mVideoView.start();
    }

    @Override
    public void onBackPressed() {
        if (mMediaController != null && mMediaController.isShowing()) {
            mMediaController.hide();
        } else {
            super.onBackPressed();
        }
    }
}