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;   }  } };}

           

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