Android SurfaceView 详解(三)

SurfaceView 示波器的例子：直接上代码了就

该程序会根据单击的按钮在屏幕上自动绘制正弦波和余弦波形。程序每次绘制时只需要绘制(更新)当前点的波形，前面已经绘制的波形无须更新，利用了SurfaceHolder的lockCanvas(Rect r)方法

1.布局文件Layout/show_wave.xml:

<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation ="vertical" android:layout_width="wrap_content" android:layout_height="wrap_content"> <Button android:id="@+id/sin" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="正弦曲线" /> <Button android:id="@+id/cos" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="余弦曲线" /> <SurfaceView android:id="@+id/show" android:layout_width="wrap_content" android:layout_height="wrap_content" /> </LinearLayout>

2.主界面Activity：ShowWave

package com.infy.configuration; 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.view.SurfaceHolder; import android.view.SurfaceView; import android.view.View; import android.view.SurfaceHolder.Callback; import android.view.View.OnClickListener; import android.widget.Button; public class ShowWave extends Activity{ private SurfaceHolder holder; private Paint paint; final int HEIGHT=320; final int WIDTH=320; final int X_OFFSET = 5; private int cx = X_OFFSET; //实际的Y轴的位置 int centerY = HEIGHT /2; Timer timer = new Timer(); TimerTask task = null; @Override protected void onCreate(Bundle savedInstanceState) { // TODO Auto-generated method stub super.onCreate(savedInstanceState); setContentView(R.layout.show_wave); final SurfaceView surface = (SurfaceView)findViewById(R.id.show); //初始化SurfaceHolder对象 holder = surface.getHolder(); paint = new Paint(); paint.setColor(Color.GREEN); paint.setStrokeWidth(3); Button sin =(Button)findViewById(R.id.sin); Button cos =(Button)findViewById(R.id.cos); OnClickListener listener = (new OnClickListener() { @Override public void onClick(final View source) { // TODO Auto-generated method stub drawBack(holder); cx = X_OFFSET; if(task != null){ task.cancel(); } task = new TimerTask() { @Override public void run() { int cy = source.getId() == R.id.sin ? centerY -(int)(100 * Math.sin((cx -5) *2 * Math.PI/150)): centerY -(int)(100 * Math.cos((cx-5)*2*Math.PI/150)); Canvas canvas = holder.lockCanvas(new Rect(cx,cy-2,cx+2,cy+2)); canvas.drawPoint(cx, cy, paint); cx++; if(cx >WIDTH){ task.cancel(); task = null; } holder.unlockCanvasAndPost(canvas); } }; timer.schedule(task, 0,30); } }); sin.setOnClickListener(listener); cos.setOnClickListener(listener); holder.addCallback(new Callback() { public void surfaceChanged(SurfaceHolder holder,int format,int width,int height){ drawBack(holder); } @Override public void surfaceCreated(SurfaceHolder holder) { // TODO Auto-generated method stub } @Override public void surfaceDestroyed(SurfaceHolder holder) { // TODO Auto-generated method stub timer.cancel(); } }); } private void drawBack(SurfaceHolder holder){ Canvas canvas = holder.lockCanvas(); //绘制白色背景 canvas.drawColor(Color.WHITE); Paint p = new Paint(); p.setColor(Color.BLACK); p.setStrokeWidth(2); //绘制坐标轴 canvas.drawLine(X_OFFSET, centerY, WIDTH, centerY, p); canvas.drawLine(X_OFFSET, 40, X_OFFSET, HEIGHT, p); holder.unlockCanvasAndPost(canvas); holder.lockCanvas(new Rect(0,0,0,0)); holder.unlockCanvasAndPost(canvas); } }

3.最后显示结果：

a.正弦曲线

b.余弦曲线：