21天学习android开发教程之SurfaceView

上一篇文章介绍了mediaplayer相关内容，这次用两篇文章来介绍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，我这里就直接在普通的用户界面调用surfaceholder的lockcanvas和unlockcanvasandpost。
先来看看程序运行的截图：

 

截图1主要演示了直接把正弦波绘画在surfaceview上 

 

对比上面的左右两图，右图用.lockcanvas(null)，而左图用.lockcanvas(new rect(oldx, 0, oldx + length,getwindowmanager().getdefaultdisplay().getheight()))，对比一下两个效果，由于左图是按指定rect绘画，所以效率会比右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。

接下来贴出main.xml的源码:

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

接下来贴出程序源码：

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);

    }
}

以上就是本文的全部内容，希望对大家学习android软件编程有所帮助。