MediaPlayer.setLooping(true)

如果你想让MediaPlayer循环播放视频，可以使用`setLooping(true)`方法。这样设置后，当视频播放完毕时，MediaPlayer会自动重新开始播放。

下面是修改后的示例代码：

import android.media.MediaPlayer;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

import androidx.appcompat.app.AppCompatActivity;

public class VideoPlayerActivity extends AppCompatActivity implements View.OnClickListener {

    private MediaPlayer mediaPlayer;

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

        Button button1 = findViewById(R.id.button1);
        Button button2 = findViewById(R.id.button2);
        Button button3 = findViewById(R.id.button3);

        button1.setOnClickListener(this);
        button2.setOnClickListener(this);
        button3.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.button1:
                playVideo(R.raw.video1);
                break;
            case R.id.button2:
                playVideo(R.raw.video2);
                break;
            case R.id.button3:
                playVideo(R.raw.video3);
                break;
        }
    }

    private void playVideo(int resourceId) {
        if (mediaPlayer != null && mediaPlayer.isPlaying()) {
            mediaPlayer.stop();
            mediaPlayer.release();
            mediaPlayer = null;
        }

        mediaPlayer = MediaPlayer.create(this, resourceId);
        mediaPlayer.setLooping(true);  // 设置循环播放
        mediaPlayer.start();
    }
}

现在当你点击按钮播放视频时，MediaPlayer会循环播放视频直到手动停止。