Android SurfaceView概述

简介：SurfaceView继承自View，但它与View不同，View是在UI主线程中更新画面，而SurfaceView是在一个新线程中更新画面，View的特性决定了其不适合做动画，因为如果更新画面时间过长，那么UI线程就会被正在画的函数阻塞，所以Android通常用SurfaceView做动画效果。

下面给出一个使用SurfaceView做的简单例子：

package com.yw.myapiupdate.mydraw;

import android.app.Activity;
import android.os.Bundle;
import android.view.Display;

/**
 *
 * @author yw-tony
 *
 */
public class MyDrawActivity extends Activity{
    private SurfaceViewBall ball ;
    private int width = 0;
    private int height = 0;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Display display = getWindowManager().getDefaultDisplay();
        width = display.getWidth();
        height = display.getHeight();

        ball = new SurfaceViewBall(this,width,height);
        /*ball.setOnTouchListener(new OnTouchListener() {
            float x = 0;
            float y = 0;
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                switch(event.getAction()){
                case MotionEvent.ACTION_DOWN://按下

                    ball.drawThread.top += event.getY();
                    ball.drawThread.left += event.getX();
                    ball.drawThread.buttom += event.getY();
                    ball.drawThread.right += event.getX();
                    break;
                case MotionEvent.ACTION_MOVE://移动
                    //基于xy为圆心移动
                    //得到手指的坐标(x,y)
                    x = event.getRawX();
                    y = event.getRawY();
                    x = ((ball.drawThread.right - ball.drawThread.left)/2);
                    y = (ball.drawThread.buttom - ball.drawThread.top)/2;

                    ball.drawThread.top = (int) (event.getRawY()+y);
                    ball.drawThread.left = (int) (event.getRawX()+x);
                    ball.drawThread.right = (int)(200+event.getX()+x);
                    ball.drawThread.buttom = (int)(200+event.getY()+y);

                    log.e("getRawX", ""+event.getRawX());
                    log.e("getRawY", ""+event.getRawY());
                    log.e("getX", ""+event.getX());
                    log.e("getRawY", ""+event.getY());

//                    ball.drawThread.top += 20;
//                    ball.drawThread.left += event.getRawX();
//                    ball.drawThread.buttom += event.getRawY();
//                    ball.drawThread.right += event.getRawX();
                    break;
                case MotionEvent.ACTION_UP://弹起
                    ball.drawThread.top += 20;
                    ball.drawThread.buttom += 20;
                    ball.drawThread.top += event.getRawY();
                    ball.drawThread.left += event.getRawX();
                    ball.drawThread.buttom += event.getRawY();
                    ball.drawThread.right += event.getRawX();
                    break;
                }
                return true;
            }
        });*/
        setContentView(ball);
    }
    /**
     * 屏幕触摸事件
     */
    /*@Override
    public boolean onTouchEvent(MotionEvent event) {
        switch(event.getAction()){
        case MotionEvent.ACTION_DOWN://按下
            ball.drawThread.top += event.getY();
            ball.drawThread.left += event.getX();
            ball.drawThread.buttom += event.getY();
            ball.drawThread.right += event.getX();
            break;
        case MotionEvent.ACTION_MOVE://移动
            ball.drawThread.top += event.getRawY();
//            ball.drawThread.left += event.getRawX();
//            ball.drawThread.buttom += event.getRawY();
//            ball.drawThread.right += event.getRawX();
            break;
        case MotionEvent.ACTION_UP://弹起
            ball.drawThread.top += event.getRawY();
            ball.drawThread.left += event.getRawX();
            ball.drawThread.buttom += event.getRawY();
            ball.drawThread.right += event.getRawX();
            break;
        }

        return true;
    }*/
    @Override
    public void onBackPressed() {
        ball.drawThread.isRun = false;
        super.onBackPressed();
    }
}

MySurfaceView.java

package com.yw.myapiupdate.mydraw;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Rect;
import android.view.SurfaceHolder;
import android.view.SurfaceView;

public class SurfaceViewBall extends SurfaceView implements SurfaceHolder.Callback{
    private SurfaceHolder holder;
    public DrawThread drawThread ;
    private int width = 0;//屏幕宽度
    private int height = 0;//屏幕高度
    public SurfaceViewBall(Context context,int width ,int height) {
        super(context);
        holder = this.getHolder();//得到surfaceHolder对象
        //给holder添加回调函数
        holder.addCallback(this);
        drawThread = new DrawThread(holder);
        this.width = width;
        this.height = height;
    }
    /**
     * 当视图发生改变时执行
     */
    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width,
            int height) {

    }
    /**
     * 当创建视图时执行
     */
    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        drawThread.isRun = true;
        drawThread.start();
    }
    /**
     * 当视图销毁时执行
     */
    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        drawThread.isRun = false;
    }
    /**
     * 绘制图像的线程
     * @author yw-tony
     *
     */
    class DrawThread extends Thread{
        private SurfaceHolder drawHolder;
        public boolean isRun;
        public int top = 50;
        public int buttom = 250;
        public int left = 100;
        public int right = 300 ;
        public DrawThread(SurfaceHolder drawHolder){
            this.drawHolder = drawHolder;
        }
        @Override
        public void run() {
            int count = 0;
            boolean target = false;
            boolean targetHeightFlag = false;
            while(isRun){
                Canvas canvas = null;
                try{
                    synchronized (SurfaceViewBall.class) {
                        canvas = drawHolder.lockCanvas();//锁定画布
                        canvas.drawColor(Color.BLACK);//设置画布颜色
                        //创建画笔
                        Paint paint = new Paint();
                        paint.setTextSize(20.00f);
                        //设置画笔颜色为白色
                        paint.setColor(Color.WHITE);
                        //创建矩形区域
                        /*left = left +20;
                        right = right + 20;*/
                        /*对矩形左右两边进行碰撞检测*/
                        if(left <= 0){//如果碰到左边界，则向右边移动
                            left = left +20;
                            right = right +20;
                            target   = false;
                        }else if(right >= width){//如果碰到右边界则向左边移动
                            left = left -20;
                            right = right - 20;
                            target = true;
                        }else{
                            if(target){
                                left = left -20;
                                right = right - 20;
                            }else{
                                left = left +20;
                                right = right + 20;
                            }

                        }
                        /*对矩形上下两边进行碰撞检测*/
                        if(top<=0){//如果矩形碰到顶部
                            top = top+10;
                            buttom = buttom + 10;
                            targetHeightFlag = false;
                        }else if(buttom >= height){//如果矩形碰到底部
                            top = top-10;
                            buttom = buttom - 10;
                            targetHeightFlag = true;
                        }else{//按正常流程执行
                            if(targetHeightFlag){
                                top = top-10;
                                buttom = buttom - 10;
                            }else{
                                top = top+10;
                                buttom = buttom + 10;
                            }
                        }

                        Rect rect = new Rect(left,top,right,buttom);
                        //绘制矩形区域
                        canvas.drawRect(rect, paint);
                        //绘制字体
                        canvas.drawText("这是第"+(count++)+"秒", 100, 300, paint);
                        //休眠时间为1秒
                        if(canvas != null){
                            holder.unlockCanvasAndPost(canvas);//结束画布锁定，并提交改变
                        }
                        Thread.sleep(50);
                    }
                }catch(Exception e){

                }finally{
                }
            }
        }
    }

}