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:
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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="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：
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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。
