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>> 这里和双缓冲没有什么关系,要注意!
请不要误导大众.这个不是双缓冲.
为什么会比左边的速度快,可能你自己都没明白。
双线程实现相当于是跳帧,装载速度大于绘制速度,某些图片没有进行绘制。而单线程实现,则每个图片都绘制。
例:当装载完第3个图片时,才刚刚完成绘制图片1
这时,绘制线程再次循环,则绘制的图片会是图片3,而图片2,则没进行绘制
>>
本文来自 ,引用必须注明出处!
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 {
-
- Button btnSingleThread, btnDoubleThread;
- SurfaceView sfv;
- SurfaceHolder sfh;
- ArrayList<Integer> imgList = new ArrayList<Integer>();
- int imgWidth, imgHeight;
- Bitmap bitmap;
-
- @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());
- }
-
- class ClickEvent implements View.OnClickListener {
-
- @Override
- public void onClick(View v) {
-
- if (v == btnSingleThread) {
- new Load_DrawImage(0, 0).start();
- } else if (v == btnDoubleThread) {
- new LoadImage().start();
- new DrawImage(imgWidth + 10, 0).start();
- }
-
- }
-
- }
-
- 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");
-
-
- Field[] fields = R.drawable.class.getDeclaredFields();
- for (Field field : fields) {
- if (!"icon".equals(field.getName()))
- {
- int index = 0;
- try {
- index = field.getInt(R.drawable.class);
- } catch (IllegalArgumentException e) {
-
- e.printStackTrace();
- } catch (IllegalAccessException e) {
-
- e.printStackTrace();
- }
-
- imgList.add(index);
- }
- }
-
- Bitmap bmImg = BitmapFactory.decodeResource(getResources(),
- imgList.get(0));
- imgWidth = bmImg.getWidth();
- imgHeight = bmImg.getHeight();
- }
-
- @Override
- public void surfaceDestroyed(SurfaceHolder holder) {
- Log.i("Surface:", "Destroy");
-
- }
-
- }
-
-
-
-
- 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);
- }
- }
- };
-
-
-
-
- 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) {
- 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);
- }
- }
- }
- };
-
-
-
-
- class LoadImage extends Thread {
- int imgIndex = 0;
-
- public void run() {
- while (true) {
- bitmap = BitmapFactory.decodeResource(getResources(),
- imgList.get(imgIndex));
- imgIndex++;
- if (imgIndex == imgList.size())
- imgIndex = 0;
- }
- }
- };
- }
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