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Android提高21篇之三：SurfaceView与多线程配合使用

       上节中简单介绍了SurfaceView的基本使用方法，本节主要讲解SurfaceView与多线程的混搭。SurfaceView与多线程混搭，是为了防止动画闪烁而实现的一种多线程应用。android的多线程用法与JAVA的多线程用法完全一样，本文不做多线程方面的介绍了。直接讲解SurfaceView与多线程的混合使用，即开一条线程专门读取图片，另外一条线程专门绘图。

       本文程序运行截图如下，左边是开单个线程读取并绘图，右边是开两个线程，一个专门读取图片，一个专门绘图：

Android提高21篇之三：SurfaceView与多线程配合使用

       对比一下，右边动画的帧速明显比左边的快，左右两者都没使用Thread.sleep()。为什么要开两个线程一个读一个画，而不去开两个线程像左边那样都“边读边画”呢？因为SurfaceView每次绘图都会锁定Canvas，也就是说同一片区域这次没画完下次就不能画，因此要提高动画播放的效率，就得开一条线程专门画图，开另外一条线程做预处理的工作。

       main.xml的源码：
XML/HTML代码
  1. <linearlayout xmlns:android="http://schemas.android.com/apk/res/android"   
  2.         android:layout_width="fill_parent" android:layout_height="fill_parent"  
  3.         android:orientation="vertical">  
  4.   
  5.         <linearlayout android:id="@+id/LinearLayout01"   
  6.                 android:layout_width="wrap_content" android:layout_height="wrap_content">  
  7.                 <button android:id="@+id/Button01" android:layout_width="wrap_content"   
  8.                         android:layout_height="wrap_content" android:text="单个独立线程">  
  9.                 <button android:id="@+id/Button02" android:layout_width="wrap_content"   
  10.                         android:layout_height="wrap_content" android:text="两个独立线程">  
  11.           
  12.         <surfaceview android:id="@+id/SurfaceView01"   
  13.                 android:layout_width="fill_parent" android:layout_height="fill_parent">  

       本文程序的源码：

Java代码
  1. package com.testSurfaceView;  
  2.   
  3. import java.lang.reflect.Field;  
  4. import java.util.ArrayList;  
  5. import android.app.Activity;  
  6. import android.graphics.Bitmap;  
  7. import android.graphics.BitmapFactory;  
  8. import android.graphics.Canvas;  
  9. import android.graphics.Paint;  
  10. import android.graphics.Rect;  
  11. import android.os.Bundle;  
  12. import android.util.Log;  
  13. import android.view.SurfaceHolder;  
  14. import android.view.SurfaceView;  
  15. import android.view.View;  
  16. import android.widget.Button;  
  17.   
  18. public class testSurfaceView extends Activity {  
  19.         /** Called when the activity is first created. */  
  20.         Button btnSingleThread, btnDoubleThread;  
  21.         SurfaceView sfv;  
  22.         SurfaceHolder sfh;  
  23.         ArrayList imgList = new ArrayList();  
  24.         int imgWidth, imgHeight;  
  25.         Bitmap bitmap;//独立线程读取，独立线程绘图  
  26.   
  27.         @Override  
  28.         public void onCreate(Bundle savedInstanceState) {  
  29.                 super.onCreate(savedInstanceState);  
  30.                 setContentView(R.layout.main);  
  31.   
  32.                 btnSingleThread = (Button) this.findViewById(R.id.Button01);  
  33.                 btnDoubleThread = (Button) this.findViewById(R.id.Button02);  
  34.                 btnSingleThread.setOnClickListener(new ClickEvent());  
  35.                 btnDoubleThread.setOnClickListener(new ClickEvent());  
  36.                 sfv = (SurfaceView) this.findViewById(R.id.SurfaceView01);  
  37.                 sfh = sfv.getHolder();  
  38.                 sfh.addCallback(new MyCallBack());// 自动运行surfaceCreated以及surfaceChanged  
  39.         }  
  40.   
  41.         class ClickEvent implements View.OnClickListener {  
  42.   
  43.                 @Override  
  44.                 public void onClick(View v) {  
  45.   
  46.                         if (v == btnSingleThread) {  
  47.                                 new Load_DrawImage(0, 0).start();//开一条线程读取并绘图  
  48.                         } else if (v == btnDoubleThread) {  
  49.                                 new LoadImage().start();//开一条线程读取  
  50.                                 new DrawImage(imgWidth + 10, 0).start();//开一条线程绘图  
  51.                         }  
  52.   
  53.                 }  
  54.   
  55.         }  
  56.   
  57.         class MyCallBack implements SurfaceHolder.Callback {  
  58.   
  59.                 @Override  
  60.                 public void surfaceChanged(SurfaceHolder holder, int format, int width,  
  61.                                 int height) {  
  62.                         Log.i("Surface:", "Change");  
  63.   
  64.                 }  
  65.   
  66.                 @Override  
  67.                 public void surfaceCreated(SurfaceHolder holder) {  
  68.                         Log.i("Surface:", "Create");  
  69.   
  70.                         // 用反射机制来获取资源中的图片ID和尺寸  
  71.                         Field[] fields = R.drawable.class.getDeclaredFields();  
  72.                         for (Field field : fields) {  
  73.                                 if (!"icon".equals(field.getName()))// 除了icon之外的图片  
  74.                                 {  
  75.                                         int index = 0;  
  76.                                         try {  
  77.                                                 index = field.getInt(R.drawable.class);  
  78.                                         } catch (IllegalArgumentException e) {  
  79.                                                 // TODO Auto-generated catch block  
  80.                                                 e.printStackTrace();  
  81.                                         } catch (IllegalAccessException e) {  
  82.                                                 // TODO Auto-generated catch block  
  83.                                                 e.printStackTrace();  
  84.                                         }  
  85.                                         // 保存图片ID  
  86.                                         imgList.add(index);  
  87.                                 }  
  88.                         }  
  89.                         // 取得图像大小  
  90.                         Bitmap bmImg = BitmapFactory.decodeResource(getResources(),  
  91.                                         imgList.get(0));  
  92.                         imgWidth = bmImg.getWidth();  
  93.                         imgHeight = bmImg.getHeight();  
  94.                 }  
  95.   
  96.                 @Override  
  97.                 public void surfaceDestroyed(SurfaceHolder holder) {  
  98.                         Log.i("Surface:", "Destroy");  
  99.   
  100.                 }  
  101.   
  102.         }  
  103.   
  104.         /* 
  105.          * 读取并显示图片的线程 
  106.          */  
  107.         class Load_DrawImage extends Thread {  
  108.                 int x, y;  
  109.                 int imgIndex = 0;  
  110.   
  111.                 public Load_DrawImage(int x, int y) {  
  112.                         this.x = x;  
  113.                         this.y = y;  
  114.                 }  
  115.   
  116.                 public void run() {  
  117.                         while (true) {  
  118.                                 Canvas c = sfh.lockCanvas(new Rect(this.x, this.y, this.x  
  119.                                                 + imgWidth, this.y + imgHeight));  
  120.                                 Bitmap bmImg = BitmapFactory.decodeResource(getResources(),  
  121.                                                 imgList.get(imgIndex));  
  122.                                 c.drawBitmap(bmImg, this.x, this.y, new Paint());  
  123.                                 imgIndex++;  
  124.                                 if (imgIndex == imgList.size())  
  125.                                         imgIndex = 0;  
  126.   
  127.                                 sfh.unlockCanvasAndPost(c);// 更新屏幕显示内容  
  128.                         }  
  129.                 }  
  130.         };  
  131.   
  132.         /* 
  133.          * 只负责绘图的线程 
  134.          */  
  135.         class DrawImage extends Thread {  
  136.                 int x, y;  
  137.   
  138.                 public DrawImage(int x, int y) {  
  139.                         this.x = x;  
  140.                         this.y = y;  
  141.                 }  
  142.   
  143.                 public void run() {  
  144.                         while (true) {  
  145.                                 if (bitmap != null) {//如果图像有效  
  146.                                         Canvas c = sfh.lockCanvas(new Rect(this.x, this.y, this.x  
  147.                                                         + imgWidth, this.y + imgHeight));  
  148.   
  149.                                         c.drawBitmap(bitmap, this.x, this.y, new Paint());  
  150.   
  151.                                         sfh.unlockCanvasAndPost(c);// 更新屏幕显示内容  
  152.                                 }  
  153.                         }  
  154.                 }  
  155.         };  
  156.   
  157.         /* 
  158.          * 只负责读取图片的线程 
  159.          */  
  160.         class LoadImage extends Thread {  
  161.                 int imgIndex = 0;  
  162.   
  163.                 public void run() {  
  164.                         while (true) {  
  165.                                 bitmap = BitmapFactory.decodeResource(getResources(),  
  166.                                                 imgList.get(imgIndex));  
  167.                                 imgIndex++;  
  168.                                 if (imgIndex == imgList.size())//如果到尽头则重新读取  
  169.                                         imgIndex = 0;  
  170.                         }  
  171.                 }  
  172.         };  
  173. }  

 

Tags:SurfaceView,线程,Canvas | 2013/5/22 | 发表评论

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