SurfaceView

介绍

使用场景：
播放视频
绘制滚动图形
画板功能
歌词滚动
飞机大战

特点：

频繁的更新UI，内有双缓冲机制

代码

布局：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <SurfaceView
        android:id="@+id/surfaceview"
        android:layout_above="@id/buttonGroup"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />
    <LinearLayout
        android:id="@+id/buttonGroup"
        android:layout_alignParentBottom="true"
        android:layout_width="match_parent"
        android:orientation="vertical"
        android:layout_height="wrap_content">
        <SeekBar
            android:id="@+id/seekbar"
            android:layout_width="match_parent"
            android:layout_height="wrap_content" />
        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content">
            <Button
                android:id="@+id/last"
                android:layout_weight="1"
                android:onClick="click"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="倒退"/>
            <Button
                android:id="@+id/play"
                android:layout_weight="1"
                android:onClick="click"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="播放"/>
            <Button
                android:id="@+id/stop"
                android:layout_weight="1"
                android:onClick="click"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="停止"/>
            <Button
                android:id="@+id/nest"
                android:layout_weight="1"
                android:onClick="click"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="快进"/>
        </LinearLayout>

    </LinearLayout>

</RelativeLayout>

MainActivity:：

surfaceview：一个SurfaceView对应一个SurfaceHolder
surfaceholder：持有者，不能直接操作SurfaceView，通过SurfaceHolder控制

画画：paint+canves
new Paint():
setColor();
setStrokeWidth() 画笔宽度（画图）
setTextSize() 文字大小
setAntiAlias(); 抗锯齿 默认false
.
holder.lockCanves() 锁定画布
unlockCanvasAndPost();解除锁定
canves.drawPiont(X,Y,paint)

package com.example.day11;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;

import android.media.MediaPlayer;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;
import android.widget.SeekBar;

import java.io.IOException;

public class MainActivity extends AppCompatActivity implements SurfaceHolder.Callback {

    SurfaceView surfaceView;
    MediaPlayer mediaPlayer=new MediaPlayer();
    SurfaceHolder surfaceHolder;

    SeekBar seekBar;

    int isPlay=0;

    Handler handler=new Handler(){
        @Override
        public void handleMessage(@NonNull Message msg) {
            super.handleMessage(msg);
            if (msg.what==101) {
                Log.i("yu", "设置进度条： "+isPlay);
                seekBar.setProgress(isPlay);
            }
        }
    };
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        seekBar=findViewById(R.id.seekbar);

        initvideo();
        initplay();

        seekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
            int aa=0;
            @Override
            public void onProgressChanged(SeekBar seekBar, int i, boolean b) {
                aa=i;
            }

            @Override
            public void onStartTrackingTouch(SeekBar seekBar) {

            }

            @Override
            public void onStopTrackingTouch(SeekBar seekBar) {
                isPlay=aa;
                mediaPlayer.seekTo(isPlay);
            }
        });

    }

    private void setProgress() {
        //视频长度
        int max = mediaPlayer.getDuration();
        seekBar.setMax(max);
    }

    private void initplay() {
        try {
            mediaPlayer.setDataSource("http://uvideo.spriteapp.cn/video/2019/0512/56488d0a-7465-11e9-b91b-1866daeb0df1_wpd.mp4");
            mediaPlayer.prepareAsync();
            mediaPlayer.setOnPreparedListener(new MediaPlayer.OnPreparedListener() {
                @Override
                public void onPrepared(MediaPlayer mediaPlayer) {
                    setProgress();
                }
            });
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private void initvideo() {
        surfaceView=findViewById(R.id.surfaceview);
        surfaceHolder=surfaceView.getHolder();
        surfaceHolder.addCallback(this);
    }

    //创建
    @Override
    public void surfaceCreated(SurfaceHolder surfaceHolder) {
        mediaPlayer.setDisplay(surfaceHolder);
    }
    //改变
    @Override
    public void surfaceChanged(SurfaceHolder surfaceHolder, int i, int i1, int i2) {

    }
    //销毁
    @Override
    public void surfaceDestroyed(SurfaceHolder surfaceHolder) {
        if (mediaPlayer!=null) {
            mediaPlayer.stop();
            mediaPlayer.release();//释放资源
            mediaPlayer=null;
        }

    }

    public void click(View view) {
        switch (view.getId()){
            //倒退
            case R.id.last:


                break;
                //播放
            case R.id.play:
                if (!mediaPlayer.isPlaying()) {
                    mediaPlayer.start();
                    new MyThread().start();
                }else if(mediaPlayer.isPlaying()){
                    mediaPlayer.pause();
                }
                break;
                //停止
            case R.id.stop:
                if (mediaPlayer.isPlaying()) {
                    mediaPlayer.stop();
                }

                break;
                //快进
            case R.id.nest:

                break;

        }
    }

    private class MyThread extends Thread{
        @Override
        public void run() {

            while (mediaPlayer.isPlaying()) {
                isPlay = mediaPlayer.getCurrentPosition();
                Log.i("yu", "不断读取； "+isPlay);
                handler.sendEmptyMessage(101);
                try {
                    Thread.sleep(500);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

滚动歌词

package com.example.day11_1;

import androidx.appcompat.app.AppCompatActivity;

import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.PorterDuff;
import android.os.Bundle;
import android.view.Surface;
import android.view.SurfaceHolder;
import android.view.SurfaceView;

public class MainActivity extends AppCompatActivity implements SurfaceHolder.Callback {


    SurfaceView surfaceView;
    SurfaceHolder holder;

    int x=0;
    int y=100;

    int x1=200;
    int y1=300;

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

        init();

    }

    private void init() {
        surfaceView=findViewById(R.id.surfaceview);
        holder=surfaceView.getHolder();
        holder.addCallback(this);
    }

    @Override
    public void surfaceCreated(SurfaceHolder surfaceHolder) {
        new MyThread().start();
    }

    @Override
    public void surfaceChanged(SurfaceHolder surfaceHolder, int i, int i1, int i2) {

    }

    @Override
    public void surfaceDestroyed(SurfaceHolder surfaceHolder) {

    }

    private class MyThread extends Thread{
        @Override
        public void run() {
            Paint paint = new Paint();
            paint.setTextSize(50);//字体大小
            paint.setStrokeWidth(30); //画笔宽度
            paint.setColor(Color.BLUE);//颜色
            paint.setAntiAlias(true);//抗锯齿


            while (true) {
                Canvas canvas = holder.lockCanvas();

                if (canvas==null) {
                    break;
                }
                if (x==getWindowManager().getDefaultDisplay().getWidth()) {
                    x=0;
                }

                if (y1==getWindowManager().getDefaultDisplay().getHeight()) {
                    y1=0;
                }
                //擦除之前的
                canvas.drawColor(Color.WHITE, PorterDuff.Mode.CLEAR);

                canvas.drawText("aaa",x+=5,y,paint);
                canvas.drawBitmap(BitmapFactory.decodeResource(getResources(),R.mipmap.ic_launcher),x1,y1+=5,paint);

                holder.unlockCanvasAndPost(canvas);
            }

        }
    }
}