SurfaceView和View的明显不同在于Surface不需要通过线程来更新视图，但在绘制之前必须使用lockCanvas方法锁定画布，并得 到画布，然后绘制，完成后用unlockCanvasAndPost方法解锁画布。SurfaceView类的事件处理和View一样。
首先来看一个简单的框架。
绘制界面类：
[java]
package com.example.bonusball;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.RectF;
import android.util.AttributeSet;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
public class CanvasView extends SurfaceView implements SurfaceHolder.Callback
{
private SurfaceHolder myHolder;
private Paint ballPaint; // Paint used to draw the cannonball
private int screenWidth; // width of the screen
private int screenHeight; // height of the screen
private int ballRadius;
private CanvasThread myThread;
//控制循环
private boolean isLoop;
public CanvasView(Context context) {
super(context);
// TODO Auto-generated constructor stub
myHolder=this.getHolder();
myHolder.addCallback(this);
ballPaint=new Paint();
ballPaint.setColor(Color.BLUE);
isLoop = true;
}
public void fireBall(float startX,float startY)
{
System.out.println("Fire");
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width,
int height) {
// TODO Auto-generated method stub
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh)
{
super.onSizeChanged(w, h, oldw, oldh);
screenWidth = w; // store the width
screenHeight = h; // store the height
ballRadius=w/10;
}
@Override
public void surfaceCreated(SurfaceHolder holder) {
// TODO Auto-generated method stub
myThread = new CanvasThread();
System.out.println("SurfaceCreated!");
myThread.start();
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
// TODO Auto-generated method stub
// 停止循环
isLoop = false;
}
public void drawGameElements(Canvas canvas)
{
canvas.drawCircle(100, 100,ballRadius,ballPaint);
}
private class CanvasThread extends Thread
{
@Override
public void run()
{
while(true)
{
synchronized( myHolder )
{
Canvas canvas = myHolder.lockCanvas(null);//获取画布
drawGameElements(canvas);
myHolder.unlockCanvasAndPost(canvas);//解锁画布，提交画好的图像
//System.out.println("run");
}
}
}
}
}
package com.example.bonusball;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.RectF;
import android.util.AttributeSet;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
public class CanvasView extends SurfaceView implements SurfaceHolder.Callback
{
private SurfaceHolder myHolder;
private Paint ballPaint; // Paint used to draw the cannonball
private int screenWidth; // width of the screen
private int screenHeight; // height of the screen
private int ballRadius;
private CanvasThread myThread;
//控制循环
private boolean isLoop;
public CanvasView(Context context) {
super(context);
// TODO Auto-generated constructor stub
myHolder=this.getHolder();
myHolder.addCallback(this);
ballPaint=new Paint();
ballPaint.setColor(Color.BLUE);
isLoop = true;
}
public void fireBall(float startX,float startY)
{
System.out.println("Fire");
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width,
int height) {
// TODO Auto-generated method stub
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh)
{
super.onSizeChanged(w, h, oldw, oldh);
screenWidth = w; // store the width
screenHeight = h; // store the height
ballRadius=w/10;
}
@Override
public void surfaceCreated(SurfaceHolder holder) {
// TODO Auto-generated method stub
myThread = new CanvasThread();
System.out.println("SurfaceCreated!");
myThread.start();
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
// TODO Auto-generated method stub
// 停止循环
isLoop = false;
}
public void drawGameElements(Canvas canvas)
{
canvas.drawCircle(100, 100,ballRadius,ballPaint);
}
private class CanvasThread extends Thread
{
@Override
public void run()
{
while(true)
{
synchronized( myHolder )
{
Canvas canvas = myHolder.lockCanvas(null);//获取画布
drawGameElements(canvas);
myHolder.unlockCanvasAndPost(canvas);//解锁画布，提交画好的图像
//System.out.println("run");
}
}
}
}
}
事件处理 类：
[java]
package com.example.bonusball;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Rect;
import android.view.GestureDetector;
import android.view.GestureDetector.SimpleOnGestureListener;
import android.view.MotionEvent;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.widget.Toast;
public class BallActivity extends Activity {
private GestureDetector myGestureDetector;//监听手势
private CanvasView myCanvas;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
myCanvas=new CanvasView(this);
setContentView(myCanvas);
myGestureDetector = new GestureDetector(this, new MyGestureListener());
}
@Override
public boolean onTouchEvent(MotionEvent event)
{
return myGestureDetector.onTouchEvent(event);
}
private class MyGestureListener extends SimpleOnGestureListener
{
public boolean onDown(MotionEvent e1) {
Toast.makeText(getApplicationContext(), "onDown", Toast.LENGTH_SHORT).show();
return true;
}
@Override
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY)
{
System.out.println("Fling");
return true;
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.activity_ball, menu);
return true;
}
}
package com.example.bonusball;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Rect;
import android.view.GestureDetector;
import android.view.GestureDetector.SimpleOnGestureListener;
import android.view.MotionEvent;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.widget.Toast;
public class BallActivity extends Activity {
private GestureDetector myGestureDetector;//监听手势
private CanvasView myCanvas;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
myCanvas=new CanvasView(this);
setContentView(myCanvas);
myGestureDetector = new GestureDetector(this, new MyGestureListener());
}
@Override
public boolean onTouchEvent(MotionEvent event)
{
return myGestureDetector.onTouchEvent(event);
}
private class MyGestureListener extends SimpleOnGestureListener
{
public boolean onDown(MotionEvent e1) {
Toast.makeText(getApplicationContext(), "onDown", Toast.LENGTH_SHORT).show();
return true;
}
@Override
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY)
{
System.out.println("Fling");
return true;
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.activity_ball, menu);
return true;
}
}
解释几个 概念 ：
callback接口:
只要继承SurfaceView类并实现SurfaceHolder.Callback接口就可以实现一个自定义的SurfaceView 了，SurfaceHolder.Callback在底层的Surface状态发生变化的时候通知 View，SurfaceHolder.Callback具有如下的接口：
surfaceCreated(SurfaceHolder holder)：当Surface第一次创建后会立即调用该函数。程序可以在该函数中做些和绘制界面相关的初始化工作，一般情况下都是在另外的线程来绘制界面，所以不要在这个函数中绘制Surface。
surfaceChanged(SurfaceHolder holder, int format, int width,int height)：当Surface的状态（大小和格式）发生变化的时候会调用该函数，在surfaceCreated调用后该函数至少会被调用一次。
SurfaceHolder 类：
它是一个用于控制surface的接口，它提供了控制surface 的大小，格式，上面的像素，即监视其改变的。
SurfaceView的getHolder()函数可以获取SurfaceHolder对象，Surface 就在SurfaceHolder对象内。虽然Surface保存了当前窗口的像素数据，但是在使用过程中是不直接和Surface打交道的，由SurfaceHolder的Canvas lockCanvas()或 则Canvas lockCanvas()函数来获取Canvas对象，通过在Canvas上绘制内容来修改Surface中的数据。如果Surface不可编辑或则尚未 创建调用该函数会返回null，在 unlockCanvas() 和 lockCanvas()中Surface的内容是不缓存的，所以需要完全重绘Surface的内容，为了提高效率只重绘变化的部分则可以调用 lockCanvas(Rect rect)函数来指定一个rect区域，这样该区域外的内容会缓存起来。在调用lockCanvas函数获取Canvas后，SurfaceView会获 取Surface的一个同步锁直到调用unlockCanvasAndPost(Canvas canvas)函数才释放该锁，这里的同步机制保证在Surface绘制过程中不会被改变（被摧毁、修改）。
最后来看一个复杂一些的例子 ，结合了之前的手势操作。
