要实现不获得系统音频焦点播放视频（仅播放视频而无音频），同时不停止后台音乐，可以使用MediaPlayer和AudioManager类来控制音频焦点。以下是一个示例代码：

import android.content.Context;
import android.media.AudioManager;
import android.media.MediaPlayer;
import android.net.Uri;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.SurfaceHolder;
import android.view.SurfaceView;

import java.io.IOException;

public class MainActivity extends AppCompatActivity implements SurfaceHolder.Callback, MediaPlayer.OnPreparedListener {
    private SurfaceView mSurfaceView;
    private SurfaceHolder mSurfaceHolder;
    private MediaPlayer mMediaPlayer;
    private AudioManager mAudioManager;
    private boolean mAudioFocusGranted = false;

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

        mSurfaceView = findViewById(R.id.surfaceView);
        mSurfaceHolder = mSurfaceView.getHolder();
        mSurfaceHolder.addCallback(this);

        mMediaPlayer = new MediaPlayer();
        mMediaPlayer.setOnPreparedListener(this);

        mAudioManager = (AudioManager) getSystemService(Context.AUDIO_SERVICE);
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        mMediaPlayer.setDisplay(holder);
        playVideo("YOUR_VIDEO_URI");
    }

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

    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        mMediaPlayer.release();
    }

    @Override
    public void onPrepared(MediaPlayer mp) {
        if (mAudioFocusGranted) {
            mp.start();
        }
    }

    private void playVideo(String videoUri) {
        try {
            mMediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
            mMediaPlayer.setDataSource(this, Uri.parse(videoUri));
            mMediaPlayer.prepareAsync();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private void requestAudioFocus() {
        AudioManager.OnAudioFocusChangeListener focusChangeListener = new AudioManager.OnAudioFocusChangeListener() {
            @Override
            public void onAudioFocusChange(int focusChange) {

            }
        };

        int result = mAudioManager.requestAudioFocus(focusChangeListener, AudioManager.STREAM_MUSIC, AudioManager.AUDIOFOCUS_GAIN);
        if (result == AudioManager.AUDIOFOCUS_REQUEST_GRANTED) {
            mAudioFocusGranted = true;
        }
    }

    private void abandonAudioFocus() {
        mAudioManager.abandonAudioFocus(null);
        mAudioFocusGranted = false;
    }

    @Override
    protected void onResume() {
        super.onResume();
        requestAudioFocus();
    }

    @Override
    protected void onPause() {
        super.onPause();
        abandonAudioFocus();
        mMediaPlayer.pause();
    }
}

请注意替换示例代码中的YOUR_VIDEO_URI为实际视频的URI。此代码中的playVideo方法使用MediaPlayer类播放视频，并在准备完成后开始播放视频。requestAudioFocus方法请求音频焦点，abandonAudioFocus方法放弃音频焦点。在onResume方法中请求音频焦点，在onPause方法中放弃音频焦点并暂停视频播放。