使用SurfaceView实现视频弹幕

package com.example.app2;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.PixelFormat;
import android.graphics.PorterDuff;
import android.media.MediaPlayer;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.text.TextUtils;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
public class MainActivity extends AppCompatActivity implements SurfaceHolder.Callback {
private SurfaceView mSvVideo;
private SurfaceView mSvDanMu;
private EditText mEd;
private MediaPlayer mediaPlayer;
private SurfaceHolder svVideoHolder, svDanMuHolder;
private boolean isPlay = true;
List<DanMuBean  list = new ArrayList< ();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// 创建MediaPlayer
initPlayer();
// 初始化视图
initView();
}
private void initPlayer() {
if (mediaPlayer == null) {
mediaPlayer = new MediaPlayer();
}
// 重置
mediaPlayer.reset();
try {
mediaPlayer.setDataSource("http://clips.vorwaerts-gmbh.de/big_buck_bunny.mp4");
mediaPlayer.prepareAsync(); //异步准备
mediaPlayer.setOnPreparedListener(new MediaPlayer.OnPreparedListener() {
@Override
public void onPrepared(MediaPlayer mp) {
mediaPlayer.setLooping(true); //是否开启循环播放
mediaPlayer.start(); //开始播放
}
});
} catch (IOException e) {
e.printStackTrace();
}
}
/**
* 发送的信息
*
* @param view
*/
public void send(View view) {
submit();
}
private void submit() {
// validate 非空判断
String edString = mEd.getText().toString().trim();
if (TextUtils.isEmpty(edString)) {
Toast.makeText(this, "edString不能为空", Toast.LENGTH_SHORT).show();
return;
}
list.add(new DanMuBean(edString)); //添加数据
mEd.setText(""); //清空
}
private void initView() {
mSvVideo = (SurfaceView) findViewById(R.id.sv_video);
mSvDanMu = (SurfaceView) findViewById(R.id.sv_danMu);
mEd = (EditText) findViewById(R.id.ed);
// 初始化 svDanMuHolder svVideoHolder
svVideoHolder = mSvVideo.getHolder();
svDanMuHolder = mSvDanMu.getHolder();
// 添加监听
svVideoHolder.addCallback(this);
svDanMuHolder.addCallback(this);
// 将弹幕显示在最上层, 并设置为透明
mSvDanMu.setZOrderOnTop(true);
svDanMuHolder.setFormat(PixelFormat.TRANSPARENT); //PixelFormat: 像素格式, TRANSPARENT(2):透明的; TRANSLUCENT(-3):半透明
}
/**
* surfaceCreated:创建
*
* @param holder
*/
@Override
public void surfaceCreated(SurfaceHolder holder) {
if (holder == svVideoHolder) {
mediaPlayer.setDisplay(svVideoHolder); //将内容显示在 svVideoHolder上
} else if (holder == svDanMuHolder) {
// 弹幕设置 开启线程
new Thread(new Runnable() {
@Override
public void run() {
while (isPlay) { //死循环
// 得到画笔, 设置属性
Paint paint = new Paint();
paint.setStrokeWidth(5); //设置笔画宽度
paint.setTextSize(30); //设置字体大小
paint.setColor(Color.GREEN); // 设置颜色
// 得到画布 通过lockCanvas
Canvas canvas = svDanMuHolder.lockCanvas();
if (canvas == null) {
break;
}
// 填充画布的颜色
canvas.drawColor(PixelFormat.TRANSPARENT, PorterDuff.Mode.CLEAR); //参数1: 设为透明, 参2: PorterDuff.Mode.CLEAR: 所绘制不会提交到画布上
// 设置弹幕内容
for (int i = 0; i < list.size(); i++) {
String text = list.get(i).text;
canvas.drawText(text, list.get(i).x += 1, list.get(i).y, paint);
if (list.get(i).x   mSvVideo.getWidth()) {
list.get(i).x = 0;
}
}
// 提交
svDanMuHolder.unlockCanvasAndPost(canvas);
}
}
}).start();
}
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
isPlay = false;
}
}

<?xml version="1.0" encoding="utf-8"? 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context=".MainActivity" 
<FrameLayout
android:layout_width="match_parent"
android:layout_height="wrap_content" 
<SurfaceView
android:id="@+id/sv_video"
android:layout_width="match_parent"
android:layout_height="280dp" / 
<SurfaceView
android:id="@+id/sv_danMu"
android:layout_width="match_parent"
android:layout_height="280dp" / 
</FrameLayout 
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content" 
<EditText
android:id="@+id/ed"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1" / 
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="send"
android:text="弹幕" / 
</LinearLayout 
</LinearLayout