SurfaceView实现双缓冲避免游戏闪屏

双缓冲技术是游戏开发中的一个重要的技术，主要原理是：当一个动画争先显示时，程序又在改变它，前面还没有显示完，程序又请求重新绘制，这样屏幕就会不停地闪烁。而双驵冲技术是把要处理的图片在内存中处理好之后，再将其显示在屏幕上

双缓冲是为了防止动画闪烁而实现的一种多线程应用，基于SurfaceView的双缓冲实现很简单，开一条线程并在其中绘图即可。本文介绍基于SurfaceView的双缓冲实现，以及介绍类似的更高效的实现方法。 

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，因此要提高双缓冲的效率，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。

[1].[图片] 程序运行截图 

[2].[代码] main.xml 

01<?xml version="1.0" encoding="utf-8"?>

02<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

03    android:layout_width="fill_parent" android:layout_height="fill_parent"

04    android:orientation="vertical">

05 

06    <LinearLayout android:id="@+id/LinearLayout01"

07        android:layout_width="wrap_content" android:layout_height="wrap_content">

08        <Button android:id="@+id/Button01" android:layout_width="wrap_content"

09            android:layout_height="wrap_content" android:text="单个独立线程"></Button>

10        <Button android:id="@+id/Button02" android:layout_width="wrap_content"

11            android:layout_height="wrap_content" android:text="两个独立线程"></Button>

12    </LinearLayout>

13    <SurfaceView android:id="@+id/SurfaceView01"

14        android:layout_width="fill_parent" android:layout_height="fill_parent"></SurfaceView>

15</LinearLayout>

[3].[代码] TestSurfaceView.java 

001package com.testSurfaceView;

002 

003import java.lang.reflect.Field;

004import java.util.ArrayList;

005import android.app.Activity;

006import android.graphics.Bitmap;

007import android.graphics.BitmapFactory;

008import android.graphics.Canvas;

009import android.graphics.Paint;

010import android.graphics.Rect;

011import android.os.Bundle;

012import android.util.Log;

013import android.view.SurfaceHolder;

014import android.view.SurfaceView;

015import android.view.View;

016import android.widget.Button;

017 

018public class TestSurfaceView extends Activity {

019    /** Called when the activity is first created. */

020    Button btnSingleThread, btnDoubleThread;

021    SurfaceView sfv;

022    SurfaceHolder sfh;

023    ArrayList<Integer> imgList = new ArrayList<Integer>();

024    int imgWidth, imgHeight;

025    Bitmap bitmap;//独立线程读取，独立线程绘图

026 

027    @Override

028    public void onCreate(Bundle savedInstanceState) {

029        super.onCreate(savedInstanceState);

030        setContentView(R.layout.main);

031 

032        btnSingleThread = (Button) this.findViewById(R.id.Button01);

033        btnDoubleThread = (Button) this.findViewById(R.id.Button02);

034        btnSingleThread.setOnClickListener(new ClickEvent());

035        btnDoubleThread.setOnClickListener(new ClickEvent());

036        sfv = (SurfaceView) this.findViewById(R.id.SurfaceView01);

037        sfh = sfv.getHolder();

038        sfh.addCallback(new MyCallBack());// 自动运行surfaceCreated以及surfaceChanged

039    }

040 

041    class ClickEvent implements View.OnClickListener {

042 

043        @Override

044        public void onClick(View v) {

045 

046            if (v == btnSingleThread) {

047                new Load_DrawImage(0, 0).start();//开一条线程读取并绘图

048            } else if (v == btnDoubleThread) {

049                new LoadImage().start();//开一条线程读取

050                new DrawImage(imgWidth + 10, 0).start();//开一条线程绘图

051            }

052 

053        }

054 

055    }

056 

057    class MyCallBack implements SurfaceHolder.Callback {

058 

059        @Override

060        public void surfaceChanged(SurfaceHolder holder, int format, int width,

061                int height) {

062            Log.i("Surface:", "Change");

063 

064        }

065 

066        @Override

067        public void surfaceCreated(SurfaceHolder holder) {

068            Log.i("Surface:", "Create");

069 

070            // 用反射机制来获取资源中的图片ID和尺寸

071            Field[] fields = R.drawable.class.getDeclaredFields();

072            for (Field field : fields) {

073                if (!"icon".equals(field.getName()))// 除了icon之外的图片

074                {

075                    int index = 0;

076                    try {

077                        index = field.getInt(R.drawable.class);

078                    } catch (IllegalArgumentException e) {

079                        // TODO Auto-generated catch block

080                        e.printStackTrace();

081                    } catch (IllegalAccessException e) {

082                        // TODO Auto-generated catch block

083                        e.printStackTrace();

084                    }

085                    // 保存图片ID

086                    imgList.add(index);

087                }

088            }

089            // 取得图像大小

090            Bitmap bmImg = BitmapFactory.decodeResource(getResources(),

091                    imgList.get(0));

092            imgWidth = bmImg.getWidth();

093            imgHeight = bmImg.getHeight();

094        }

095 

096        @Override

097        public void surfaceDestroyed(SurfaceHolder holder) {

098            Log.i("Surface:", "Destroy");

099 

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}