Android开发--SurfaceView的基本用法

        在Android中可以利用View来绘制一些图形，图片，但当我们开发游戏或视频时，View就不再适用，这时必须使用SurfaceView来代替View。SurfaceView相比View可以实现多线程绘图和双缓冲技术，可以使得我们的动画更加流畅。接下来简单记录一下Surface的基本用法：

        首先我们应该继承SurfaceView的类，并实现SurfaceHolder.Callback，这个接口是用来管理SurfaceView的生命周期，一共有三个方法：

             1）surfaceCreated: SurfaceView对象被创建时触发；

             2）surfaceChanged: SurfaceView的大小发生变化时触发；

             3）surfaceDestroyed: SurfaceView对象被销毁时触发；

         我们在初始化方法中得到SurfaceHolder的对象，并通过该对象的addCallback方法添加这个接口进来

private void init() {
holder = getHolder();
holder.addCallback(this);
paint = new Paint();
paint.setColor(Color.BLUE);
paint.setStyle(Paint.Style.STROKE);
}

          接下来创建我们的异步线程来进行绘图操作

private Thread myThread = new Thread(new Runnable() {

@Override
public void run() {
// TODO Auto-generated method stub
while (isLived) {
if (num <= 20) {
num++;
} else {
num = 2;
}
canvas = holder.lockCanvas();
if (canvas != null) {
canvas.drawColor(Color.BLACK);//清屏
canvas.drawCircle(100, 100, num, paint);
holder.unlockCanvasAndPost(canvas);
}
try {
Thread.sleep(1000);
} catch (Exception e) {
// TODO: handle exception
}
}
}
});

        通过lockCanvas方法我们可以得到一个加锁的Canvas，当Canvas在进行绘图时，或被锁起来。注：如果当前Canvas正在被绘制，将会返回一个null值。接下来我们绘制一个空心的圆，半径不断增加。绘制完成后将锁打开。

         然后我们在Callback接口方法中在create方法中设置标志isLived为true，然后开启线程，在destory方法中设置isLived为false

@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width,
int height) {
// TODO Auto-generated method stub

}

@Override
public void surfaceCreated(SurfaceHolder holder) {
// TODO Auto-generated method stub
isLived = true;
myThread.start();
Log.w(TAG, "surfaceCreated");
}

@Override
public void surfaceDestroyed(SurfaceHolder holder) {
// TODO Auto-generated method stub
isLived = false;
Log.w(TAG, "surfaceDestroyed");
}

附上整个类的源码

package com.example.test;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;

public class MySurfaceView extends SurfaceView implements
SurfaceHolder.Callback {

private static final String TAG = "MySurfaceView";

private SurfaceHolder holder;
private boolean isLived;
private Paint paint;
private Canvas canvas;
private int num;
private Thread myThread = new Thread(new Runnable() {

@Override
public void run() {
// TODO Auto-generated method stub
while (isLived) {
if (num <= 20) {
num++;
} else {
num = 2;
}
canvas = holder.lockCanvas();
if (canvas != null) {
canvas.drawColor(Color.BLACK);
canvas.drawCircle(100, 100, num, paint);
holder.unlockCanvasAndPost(canvas);
}
try {
Thread.sleep(1000);
} catch (Exception e) {
// TODO: handle exception
}
}
}
});

public MySurfaceView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
// TODO Auto-generated constructor stub
init();
}

public MySurfaceView(Context context, AttributeSet attrs) {
super(context, attrs);
// TODO Auto-generated constructor stub
init();
}

public MySurfaceView(Context context) {
super(context);
init();
// TODO Auto-generated constructor stub
}

private void init() {
holder = getHolder();
holder.addCallback(this);
paint = new Paint();
paint.setColor(Color.BLUE);
paint.setStyle(Paint.Style.STROKE);
}

@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width,
int height) {
// TODO Auto-generated method stub

}

@Override
public void surfaceCreated(SurfaceHolder holder) {
// TODO Auto-generated method stub
isLived = true;
myThread.start();
Log.w(TAG, "surfaceCreated");
}

@Override
public void surfaceDestroyed(SurfaceHolder holder) {
// TODO Auto-generated method stub
isLived = false;
Log.w(TAG, "surfaceDestroyed");
}

}