Android提高之SurfaceView的基本用法实例分析

前文介绍了android中mediaplayer用法的时候稍微介绍了surfaceview，surfaceview由于可以直接从内存或者dma等硬件接口取得图像数据，因此是个非常重要的绘图容器，这次我就来较为详细的介绍surfaceview的用法。网上介绍surfaceview的用法有很多，写法也层出不同，例如继承surfaceview类，或者继承surfaceholder.callback类等，这个可以根据功能实际需要自己选择，本文所述方法就直接在普通的用户界面调用surfaceholder的lockcanvas和unlockcanvasandpost。

先来看看程序运行效果的截图如下：

截图1主要演示了直接把正弦波绘画在surfaceview上。

再来看看下面两幅截图：

 

对比上面的上下两图，下图用.lockcanvas(null)，而上图用.lockcanvas(new rect(oldx, 0, oldx + length,
getwindowmanager().getdefaultdisplay().getheight()))，对比一下两个效果，由于上图是按指定rect绘画，所以效率会比下图的全控件绘画高些，并且在清屏之后(canvas.drawcolor(color.black))不会留有上次绘画的残留。

main.xml的源码如下:

<?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="简单绘画"></button>
 <button android:id="@+id/button02" android:layout_width="wrap_content"
 android:layout_height="wrap_content" android:text="定时器绘画"></button>
 </linearlayout>
 <surfaceview android:id="@+id/surfaceview01"
 android:layout_width="fill_parent" android:layout_height="fill_parent"></surfaceview>
</linearlayout>

接下来贴出java程序源码如下：

package com.testsurfaceview;
import java.util.timer;
import java.util.timertask;
import android.app.activity;
import android.graphics.canvas;
import android.graphics.color;
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 btnsimpledraw, btntimerdraw;
 surfaceview sfv;
 surfaceholder sfh;

 private timer mtimer;
 private mytimertask mtimertask;
 int y_axis[],//保存正弦波的y轴上的点
 centery,//中心线
 oldx,oldy,//上一个xy点 
 currentx;//当前绘制到的x轴上的点

 @override
 public void oncreate(bundle savedinstancestate) {
 super.oncreate(savedinstancestate);
 setcontentview(r.layout.main);
 btnsimpledraw = (button) this.findviewbyid(r.id.button01);
 btntimerdraw = (button) this.findviewbyid(r.id.button02);
 btnsimpledraw.setonclicklistener(new clickevent());
 btntimerdraw.setonclicklistener(new clickevent());
 sfv = (surfaceview) this.findviewbyid(r.id.surfaceview01);
 sfh = sfv.getholder();

 //动态绘制正弦波的定时器
 mtimer = new timer();
 mtimertask = new mytimertask();

 // 初始化y轴数据
 centery = (getwindowmanager().getdefaultdisplay().getheight() - sfv
 .gettop()) / 2;
 y_axis = new int[getwindowmanager().getdefaultdisplay().getwidth()];
 for (int i = 1; i < y_axis.length; i++) {// 计算正弦波
 y_axis[i - 1] = centery
 - (int) (100 * math.sin(i * 2 * math.pi / 180));
 }
 }
 class clickevent implements view.onclicklistener {

 @override
 public void onclick(view v) {

 if (v == btnsimpledraw) {
 simpledraw(y_axis.length-1);//直接绘制正弦波
 } else if (v == btntimerdraw) {
 oldy = centery;
 mtimer.schedule(mtimertask, 0, 5);//动态绘制正弦波
 }
 }
 }
 class mytimertask extends timertask {
 @override
 public void run() {

 simpledraw(currentx);
 currentx++;//往前进
 if (currentx == y_axis.length - 1) {//如果到了终点，则清屏重来
 cleardraw();
 currentx = 0;
 oldy = centery;
 }
 }
 }
 /*
 * 绘制指定区域
 */
 void simpledraw(int length) {
 if (length == 0)
 oldx = 0;
 canvas canvas = sfh.lockcanvas(new rect(oldx, 0, oldx + length,
 getwindowmanager().getdefaultdisplay().getheight()));// 关键:获取画布
 log.i("canvas:",
 string.valueof(oldx) + "," + string.valueof(oldx + length));
 paint mpaint = new paint();
 mpaint.setcolor(color.green);// 画笔为绿色
 mpaint.setstrokewidth(2);// 设置画笔粗细
 int y;
 for (int i = oldx + 1; i < length; i++) {// 绘画正弦波
 y = y_axis[i - 1];
 canvas.drawline(oldx, oldy, i, y, mpaint);
 oldx = i;
 oldy = y;
 }
 sfh.unlockcanvasandpost(canvas);// 解锁画布，提交画好的图像
 }
 void cleardraw() {
 canvas canvas = sfh.lockcanvas(null);
 canvas.drawcolor(color.black);// 清除画布
 sfh.unlockcanvasandpost(canvas);
 }
}

这里还需要注意一下： for (int i = oldx + 1; i < length; i++) {// 绘画正弦波 这句，在.lockcanvas()指定rect内减少循环画线的次数，可以提高绘图效率。