SurfaceView的操作类

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写一个类，继承SurfaceView，在其构造方法中，获取surfaceHolder，并得到SurfaceView的生命周期。在surfaceCreated方法里，开启绘制线程，在surfaceDestory方法里，关闭线程。在线程里，每隔50s绘制一次。绘制方法用try catch方法包起来，因为可能canvas会报空指针，在进入主屏幕的时候，或者线程没有停止，但SurfaceView已经关闭的情况下。

下面是代码

package com.example.roundprogressbar;import android.content.Context;import android.graphics.Canvas;import android.util.AttributeSet;import android.view.SurfaceHolder;import android.view.SurfaceHolder.Callback;import android.view.SurfaceView;public class MySurfaceView extends SurfaceView implements Callback, Runnable {private SurfaceHolder mSurfaceHolder;private Canvas mcCanvas;/** * 绘制线程 */private Thread mThread;/** * 线程是否在执行 */private boolean isRunning;public MySurfaceView(Context context, AttributeSet attrs) {this(context, attrs, 0);}public MySurfaceView(Context context, AttributeSet attrs, int defStyle) {super(context, attrs, defStyle);mSurfaceHolder = getHolder();mSurfaceHolder.addCallback(this);// 可获得焦点setFocusable(true);setFocusableInTouchMode(true);// 设置屏幕常亮setKeepScreenOn(true);}public MySurfaceView(Context context) {this(context, null, 0);}@Overridepublic void surfaceCreated(SurfaceHolder holder) {// 在这里开启线程isRunning = true;mThread = new Thread(this);mThread.start();}@Overridepublic void surfaceChanged(SurfaceHolder holder, int format, int width,int height) {}@Overridepublic void surfaceDestroyed(SurfaceHolder holder) {isRunning = false;}@Overridepublic void run() {while (isRunning) {//每隔50ms绘制一次long startTime=System.currentTimeMillis();draw();long endTime=System.currentTimeMillis();if(endTime-startTime<50){try {Thread.sleep(50-(endTime-startTime));} catch (InterruptedException e) {e.printStackTrace();}}}}private void draw() {try {mcCanvas = mSurfaceHolder.lockCanvas();if (mcCanvas != null) {// 在这里进行绘制操作}} catch (Exception e) {e.printStackTrace();} finally {if (mcCanvas != null) {mSurfaceHolder.unlockCanvasAndPost(mcCanvas);}}}}

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