3.SurfaceView与多线程的混搭

上一篇简单介绍了SurfaceView的基本使用，这篇就介绍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技术。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。

先看效果图，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：

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<?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

            android:id="@+id/Button02"

            android:layout_width="wrap_content"

            android:layout_height="wrap_content"

            android:text="两个独立线程"

            />

    </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：

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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, intwidth,

                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;

            }

        }

    };

}

本文转自：http://blog.csdn.net/hellogv/article/details/5986835