SurfaceView的使用方法

1. 首先获取 SurfaceCiew对象：

    final SurfaceView surface = (SurfaceView)findViewById(R.id.show);

2. 通过surface对象 获取 SurfaceHolder对象：

             holder = surface.getHolder();

3. 一旦有了 surface和holder对象，就可以进行绘图操作

   例如：

 （1） Canvas canvas = holder.lockCanvas(new Rect(cx , cy - 2  , cx + 2, cy + 2));  //或者不带参数的，表示锁定整个surface对象，获取该对象上的Canvas对象。

 （2） canvas.drawPoint(cx , cy , paint);  // 进行绘制操作

 （3） holder.unlockCanvasAndPost(canvas); //绘制完成，释放画布，提交修改，图形显示

 （4） holder.lockCanvas(new Rect(0 , 0 , 0 , 0)); //重新锁一次，“持久化”上次绘制的内容

 （5） holder.unlockCanvasAndPost(canvas);  //

----------- 示例 

package org.crazyit.image;

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.SurfaceHolder.Callback;
import android.view.SurfaceView;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;


/**
 * Description:
 * <br/>site: <a href="http://www.crazyit.org">crazyit.org</a>
 * <br/>Copyright (C), 2001-2014, Yeeku.H.Lee
 * <br/>This program is protected by copyright laws.
 * <br/>Program Name:
 * <br/>Date:
 * @author  Yeeku.H.Lee [e-mail]
 * @version  1.0
 */
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
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
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)
{
//drawBack(holder);
cx = X_OFFSET;
if(task != null)
{
task.cancel();
}
task = new TimerTask()
{
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()
{
@Override
public void surfaceChanged(SurfaceHolder holder, int format,
int width, int height)
{
drawBack(holder);
}


@Override
public void surfaceCreated(final SurfaceHolder myHolder)
{
}


@Override
public void surfaceDestroyed(SurfaceHolder holder)
{
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);
}
}