前面有关自定义View中进行了绘图，但View的绘图机制存在如下缺陷：
1、View缺乏双缓冲机制。
2、当程序需要更新View上的图像时，程序必须重绘View上显示的整张图片。
3、新线程无法直接更新View组件。
由于View存在上面缺陷，所以在游戏开发中一般使用SurfaceView来进行绘制，SurfaceView一般会与SurfaceHolder结合使用，SurfaceHolder用于向与之关联的SurfaceView上绘图，调用SurfaceView的getHolder()方法即可获取SurfaceView关联的SurfaceHolder.
SurfaceHolder提供了如下方法来获取Canvas对象：
1、Canvas lockCanvas():锁定整个SurfaceView对象，获取该Surface上的Canvas.
2、Canvas lockCanvas(Rect dirty):锁定SurfaceView上Rect划分的区域，获取该Surface上的Canvas.
两个方法返回的是同一个Canvas,但是第二个方法只对圈出来的区域进行刷新，Canvas绘图完成后通过unlockCanvasAndPost(canvas)方法来释放画布，提交修改。当调用SurfaceHolder的unlockCanvasAndPost方法之后，该方法之前所绘制的图形还处于缓冲之下，下一次lockCanvas()方法锁定的区域可能会“遮挡”它。
package com.example.erweimatest;import android.app.Activity;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import android.graphics.Rect;import android.os.Bundle;import android.view.MotionEvent;import android.view.SurfaceHolder;import android.view.SurfaceHolder.Callback;import android.view.SurfaceView;import android.view.View;import android.view.View.OnTouchListener;public class SurfaceViewTest extends Activity { private SurfaceHolder holder; private Paint paint; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); paint = new Paint(); SurfaceView surface = (SurfaceView) findViewById(R.id.show); //初始化SurfaceHolder对象 holder = surface.getHolder(); holder.addCallback(new Callback() { @Override public void surfaceDestroyed(SurfaceHolder holder) { } @Override public void surfaceCreated(SurfaceHolder holder) { //锁定整个SurfaceView Canvas canvas = holder.lockCanvas(); //绘制背景 Bitmap back = BitmapFactory.decodeResource(SurfaceViewTest.this.getResources(), R.drawable.bg); //绘制背景 canvas.drawBitmap(back, 0, 0, null); //绘制完成，释放画布，提交修改 holder.unlockCanvasAndPost(canvas); //重新锁一次，“持久化”上次所绘制内容 //本次lockCanvas会遮挡上次lockCanvas holder.lockCanvas(new Rect(0, 0, 0, 0)); holder.unlockCanvasAndPost(canvas); } @Override public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) { // TODO Auto-generated method stub } }); surface.setOnTouchListener(new OnTouchListener() { @Override public boolean onTouch(View v, MotionEvent event) { if(event.getAction() == MotionEvent.ACTION_DOWN){ int cx = (int) event.getX(); int cy = (int) event.getY(); //锁定SurfaceView的布局区域，只更新局部内容 Canvas canvas = holder.lockCanvas(new Rect(cx - 50, cy - 50, cx + 50, cy + 50)); //保存canvas当前状态 canvas.save(); //旋转画布 canvas.rotate(30, cx, cy); paint.setColor(Color.RED); //绘制红色方块 canvas.drawRect(cx - 40, cy - 40, cx, cy, paint); //恢复canvas之前的保存状态 canvas.restore(); paint.setColor(Color.GREEN); //绘制绿色方块 canvas.drawRect(cx, cy, cx + 40, cy + 40, paint); //绘制完成，释放画布，提交修改 holder.unlockCanvasAndPost(canvas); } return false; } }); }}main.xml 运行效果：
基于SurfaceView开发的示波器：
package com.example.erweimatest;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;public class ShowVawe 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) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_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() { @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() { @Override public void surfaceDestroyed(SurfaceHolder holder) { // TODO Auto-generated method stub } @Override public void surfaceCreated(SurfaceHolder holder) { // TODO Auto-generated method stub } @Override public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) { // TODO Auto-generated method stub } }); } 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); }}activity_main.xml 运行结果：
当程序每次绘制正旋波、余旋波上的当前点时，程序无须重绘整个画面，SurfaceHolder只要锁定当前绘制点的小范围即可，系统更新画面时也只要更新这个范围即可。