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Android 的 SurfaceView 双缓冲应用
来源:互联网   发布日期:2015-10-13 07:37:59   浏览:1878次  

导读: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......

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。

[图片] 程序运行截图

[代码] main.xml

<?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>

[代码] TestSurfaceView.java

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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相关热词: 双缓冲 缓冲 SurfaceView

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