Android提高第三篇之SurfaceView与多线程的混搭

 

本文来自http://blog.csdn.net/hellogv/ ，引用必须注明出处！

         上一篇简单介绍了SurfaceView的基本使用，这次就介绍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：

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 version="1.0" encoding="utf-8"?>  <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"      android:layout_width="fill_parent" android:layout_height="fill_parent"      android:orientation="vertical">        <LinearLayout android:id="@+id/LinearLayout01"          android:layout_width="wrap_content" android:layout_height="wrap_content">          <Button android:id="@+id/Button01" android:layout_width="wrap_content"              android:layout_height="wrap_content" android:text="单个独立线程"></Button>          <Button android:id="@+id/Button02" android:layout_width="wrap_content"              android:layout_height="wrap_content" android:text="两个独立线程"></Button>      </LinearLayout>      <SurfaceView android:id="@+id/SurfaceView01"          android:layout_width="fill_parent" android:layout_height="fill_parent"></SurfaceView>  </LinearLayout>  

本文程序的源码：

package com.testSurfaceView;    import java.lang.reflect.Field;  import java.util.ArrayList;  import android.app.Activity;  import android.graphics.Bitmap;  import android.graphics.BitmapFactory;  import android.graphics.Canvas;  import android.graphics.Paint;  import android.graphics.Rect;  import android.os.Bundle;  import android.util.Log;  import android.view.SurfaceHolder;  import android.view.SurfaceView;  import android.view.View;  import android.widget.Button;    public class testSurfaceView extends Activity {      /** Called when the activity is first created. */      Button btnSingleThread, btnDoubleThread;      SurfaceView sfv;      SurfaceHolder sfh;      ArrayList<Integer> imgList = new ArrayList<Integer>();      int imgWidth, imgHeight;      Bitmap bitmap;//独立线程读取，独立线程绘图         @Override      public void onCreate(Bundle savedInstanceState) {          super.onCreate(savedInstanceState);          setContentView(R.layout.main);            btnSingleThread = (Button) this.findViewById(R.id.Button01);          btnDoubleThread = (Button) this.findViewById(R.id.Button02);          btnSingleThread.setOnClickListener(new ClickEvent());          btnDoubleThread.setOnClickListener(new ClickEvent());          sfv = (SurfaceView) this.findViewById(R.id.SurfaceView01);          sfh = sfv.getHolder();          sfh.addCallback(new MyCallBack());// 自动运行surfaceCreated以及surfaceChanged       }        class ClickEvent implements View.OnClickListener {            @Override          public void onClick(View v) {                if (v == btnSingleThread) {                  new Load_DrawImage(0, 0).start();//开一条线程读取并绘图               } else if (v == btnDoubleThread) {                  new LoadImage().start();//开一条线程读取                   new DrawImage(imgWidth + 10, 0).start();//开一条线程绘图               }            }        }        class MyCallBack implements SurfaceHolder.Callback {            @Override          public void surfaceChanged(SurfaceHolder holder, int format, int width,                  int height) {              Log.i("Surface:", "Change");            }            @Override          public void surfaceCreated(SurfaceHolder holder) {              Log.i("Surface:", "Create");                // 用反射机制来获取资源中的图片ID和尺寸               Field[] fields = R.drawable.class.getDeclaredFields();              for (Field field : fields) {                  if (!"icon".equals(field.getName()))// 除了icon之外的图片                   {                      int index = 0;                      try {                          index = field.getInt(R.drawable.class);                      } catch (IllegalArgumentException e) {                          // TODO Auto-generated catch block                           e.printStackTrace();                      } catch (IllegalAccessException e) {                          // TODO Auto-generated catch block                           e.printStackTrace();                      }                      // 保存图片ID                       imgList.add(index);                  }              }              // 取得图像大小               Bitmap bmImg = BitmapFactory.decodeResource(getResources(),                      imgList.get(0));              imgWidth = bmImg.getWidth();              imgHeight = bmImg.getHeight();          }            @Override          public void surfaceDestroyed(SurfaceHolder holder) {              Log.i("Surface:", "Destroy");            }        }        /*      * 读取并显示图片的线程      */      class Load_DrawImage extends Thread {          int x, y;          int imgIndex = 0;            public Load_DrawImage(int x, int y) {              this.x = x;              this.y = y;          }            public void run() {              while (true) {                  Canvas c = sfh.lockCanvas(new Rect(this.x, this.y, this.x                          + imgWidth, this.y + imgHeight));                  Bitmap bmImg = BitmapFactory.decodeResource(getResources(),                          imgList.get(imgIndex));                  c.drawBitmap(bmImg, this.x, this.y, new Paint());                  imgIndex++;                  if (imgIndex == imgList.size())                      imgIndex = 0;                    sfh.unlockCanvasAndPost(c);// 更新屏幕显示内容               }          }      };        /*      * 只负责绘图的线程      */      class DrawImage extends Thread {          int x, y;            public DrawImage(int x, int y) {              this.x = x;              this.y = y;          }            public void run() {              while (true) {                  if (bitmap != null) {//如果图像有效                       Canvas c = sfh.lockCanvas(new Rect(this.x, this.y, this.x                              + imgWidth, this.y + imgHeight));                        c.drawBitmap(bitmap, this.x, this.y, new Paint());                        sfh.unlockCanvasAndPost(c);// 更新屏幕显示内容                   }              }          }      };        /*      * 只负责读取图片的线程      */      class LoadImage extends Thread {          int imgIndex = 0;            public void run() {              while (true) {                  bitmap = BitmapFactory.decodeResource(getResources(),                          imgList.get(imgIndex));                  imgIndex++;                  if (imgIndex == imgList.size())//如果到尽头则重新读取                       imgIndex = 0;              }          }      };  }