Android提高之SurfaceView与多线程的混搭实例

前文简单介绍了Android中SurfaceView的基本使用，本文就来介绍一下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：

对比一下可以看出，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的源码如下：

<?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>

Java程序的源码如下：

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;
  }
 }
 };
}

希望本文所述示例能对大家进行Android的SurfaceView与多线程的混搭编程有所帮助。