SurfaceView

SurfaceView介绍
1.SurfaceView和View的区别：
View 主要适用于主动更新的情况，而 surfaceView 主要适用于被动更新，例如频繁的刷新。
View 在主线程中对画面进行刷新，而 surfaceView 通常会通过一个子线程来进行页面的刷新
View 在绘图时没有使用双缓冲机制，而 surfaceView 在底层实现机制上就已经实现了双缓冲机制。
总结就是，如果你的自定义 View 需要频繁刷新，或者刷新时数据处理量很大，考虑用 SurfaceView 来替代 View。
二.双缓存机制

三.MainActivty

//java文件

package com.example.administrator.myapplication4;

import android.media.MediaPlayer;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.MediaController;
import android.widget.VideoView;

public class Main2Activity extends AppCompatActivity {
    VideoView videoView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);
        videoView=findViewById(R.id.vv);
        //设置资源
        videoView.setVideoPath("http://wvideo.spriteapp.cn/video/2019/0812/5d50ae80664f1_wpd.mp4");
        videoView.setOnPreparedListener(new MediaPlayer.OnPreparedListener() {
            @Override
            public void onPrepared(MediaPlayer mp) {
                videoView.start();
            }
        });

        //控制器：自带进度条和播放暂停按钮
        videoView.setMediaController(new MediaController(this));
    }
}
//效果图

//MainActivity2代码

//java文件

package com.example.administrator.myapplication4;

import android.media.MediaPlayer;
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;
import android.widget.Button;
import android.widget.SeekBar;
import android.widget.TextView;

import java.io.IOException;
import java.util.Timer;
import java.util.TimerTask;

public class SurfaceViewActivity extends AppCompatActivity implements SurfaceHolder.Callback, View.OnClickListener {
    SurfaceView surfaceView;//控件 一个Surfaceview 对应一个surfaceHolder
    SurfaceHolder surfaceHolder;//持有者,不能直接操作SurfaceView,通过他的SurfaceHolder来操作，
    MediaPlayer mediaPlayer = new MediaPlayer();//媒体资源对象
    private TextView tv_current;
    private SeekBar bar;
    private TextView tv_duration;
    private Button bt_start;
    Timer timer;
    Handler handler=new Handler(){
        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            if(msg.what==101){
                int currentPosition = mediaPlayer.getCurrentPosition();//获得当前进度
                bar.setProgress(currentPosition);//给金福条设置
                int duration = mediaPlayer.getDuration();//总时长
                bar.setMax(duration);
            }
        }
    };
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_surface_view);
        initView();
        initPalyer();
        initTimer();
    }
    //定时器：每隔一段时间获取视频当前的进度
    private void initTimer() {
        timer=new Timer();
        timer.schedule(new TimerTask() {
            @Override
            public void run() {
                handler.sendEmptyMessage(101);
            }
        },0,200);//0毫秒之后执行 每隔200毫秒再执行一次
    }

    private void initView() {
        surfaceView = findViewById(R.id.surface);
        surfaceHolder = surfaceView.getHolder();
        surfaceHolder.addCallback(this);//添加接口回调,能够获取surfaceview的生命周期

        tv_current = (TextView) findViewById(R.id.tv_current);
        tv_current.setOnClickListener(this);
        bar = (SeekBar) findViewById(R.id.bar);
        bar.setOnClickListener(this);
        tv_duration = (TextView) findViewById(R.id.tv_duration);
        tv_duration.setOnClickListener(this);
        bt_start = (Button) findViewById(R.id.bt_start);
        bt_start.setOnClickListener(this);
        bar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
            @Override
            public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {

            }

            @Override
            public void onStartTrackingTouch(SeekBar seekBar) {

            }

            @Override
            public void onStopTrackingTouch(SeekBar seekBar) {
                mediaPlayer.seekTo(seekBar.getProgress());//更新视频的进度
            }
        });
    }
    //初始化mediaplayer
    private void initPalyer() {
        try {
            mediaPlayer.setDataSource("http://wvideo.spriteapp.cn/video/2019/0812/5d50ae80664f1_wpd.mp4");
            mediaPlayer.prepareAsync();
            mediaPlayer.setOnPreparedListener(new MediaPlayer.OnPreparedListener() {
                @Override
                public void onPrepared(MediaPlayer mp) {
                    //   mediaPlayer.start();

                }
            });
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    //生命周期：创建 将mediaplayer和surfaceholder绑定一起，
    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        mediaPlayer.setDisplay(surfaceHolder);//将mediapler显示在surfaceview
    }

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

    //销毁
    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {

    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.bt_start:
                if(mediaPlayer.isPlaying()){
                    mediaPlayer.pause();
                }else{
                    mediaPlayer.start();
                }
                break;
        }
    }
}

//效果图

//MainActivity3

//java文件

package com.example.administrator.myapplication4;

import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.os.Build;
import android.support.annotation.RequiresApi;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.SurfaceHolder;
import android.view.SurfaceView;

public class GraphisActivity extends AppCompatActivity implements SurfaceHolder.Callback {
    SurfaceView surfaceView;
    SurfaceHolder surfaceHolder;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_graphis);
        surfaceView=findViewById(R.id.surface_view);
        surfaceHolder=surfaceView.getHolder();
        surfaceHolder.addCallback(this);
    }
    //画画:画笔paint+画布canves
    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        //TODO 1:画笔
        Paint paint = new Paint();
        paint.setColor(Color.GREEN);//颜色
        paint.setStrokeWidth(30);//画笔宽度
        paint.setTextSize(60);//文字的大小
        paint.setAntiAlias(true);//抗锯齿，默认false
        //TODO 2：画布
        Canvas canvas = holder.lockCanvas();//锁定  我在画的时候，不让其他人的话
        //画点
        canvas.drawPoint(200,300,paint);
        //画线
        canvas.drawLine(200,300,400,500,paint);
        //画圆
        canvas.drawOval(100,200,300,400,paint);
        //画矩形
        canvas.drawRect(300,400,500,600,paint);
        //画扇形
        canvas.drawArc(500,500,700,700,20,180,true,paint);
        //画文字：歌词滚动
        canvas.drawText("我是帅哥承谦益",800,800,paint);
        //画图片
        canvas.drawBitmap(BitmapFactory.decodeResource(getResources(),R.mipmap.ic_launcher),800,900,paint);

        holder.unlockCanvasAndPost(canvas);//解除锁定
    }

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

    }
    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {

    }
}