Android兑现局部重绘

转载自http://www.cnblogs.com/SkyD/archive/2010/11/08/1871423.html，对原作者表示感谢

首先我们来看一下本例需要用到的两个素材图片：

bj.jpg就是一个渐变图，用作背景。

question.png是一个半透明的图像，我们希望将它放在上面，围绕其圆心不断旋转。

实现代码如下package SkyD.SurfaceViewTest;

 import android.app.Activity;import android.content.Context;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.graphics.Canvas;import android.graphics.Matrix;import android.graphics.Paint;import android.os.Bundle;import android.view.SurfaceHolder;import android.view.SurfaceView; public class Main extends Activity {     @Override    public void onCreate(Bundle savedInstanceState) {       super.onCreate(savedInstanceState);       setContentView(new MySurfaceView(this));    }     // 自定义的SurfaceView子类    class MySurfaceView extends SurfaceView implements SurfaceHolder.Callback {        // 背景图       private Bitmap BackgroundImage;       // 问号图       private Bitmap QuestionImage;        SurfaceHolder Holder;        public MySurfaceView(Context context) {           super(context);           BackgroundImage = BitmapFactory.decodeResource(getResources(),                  R.drawable.bg);           QuestionImage = BitmapFactory.decodeResource(getResources(),                  R.drawable.question);            Holder = this.getHolder();// 获取holder           Holder.addCallback(this);       }        @Override       public void surfaceChanged(SurfaceHolder holder, int format, int width,              int height) {           // TODO Auto-generated method stub        }        @Override       public void surfaceCreated(SurfaceHolder holder) {           // 启动自定义线程           new Thread(new MyThread()).start();       }        @Override       public void surfaceDestroyed(SurfaceHolder holder) {           // TODO Auto-generated method stub        }        // 自定义线程类       class MyThread implements Runnable {            @Override           public void run() {              Canvas canvas = null;              int rotate = 0;// 旋转角度变量              while (true) {                  try {                     canvas = Holder.lockCanvas();// 获取画布                     Paint mPaint = new Paint();                     // 绘制背景                     canvas.drawBitmap(BackgroundImage, 0, 0, mPaint);                     // 创建矩阵以控制图片旋转和平移                     Matrix m = new Matrix();                     // 设置旋转角度                     m.postRotate((rotate += 48) % 360,                            QuestionImage.getWidth() / 2,                            QuestionImage.getHeight() / 2);                     // 设置左边距和上边距                     m.postTranslate(47, 47);                     // 绘制问号图                     canvas.drawBitmap(QuestionImage, m, mPaint);                     // 休眠以控制最大帧频为每秒约30帧                     Thread.sleep(33);                  } catch (Exception e) {                  } finally {                     Holder.unlockCanvasAndPost(canvas);// 解锁画布，提交画好的图像                  }              }           }        }     }}