android中View类的开发框架

package com.gamesurfaceview;

import android.R.integer;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.KeyEvent;

public class Activity01 extends Activity
{
private static final int REFRESH = 0x000001;
private GameSurfaceView mGameSurfaceView = null;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.mGameSurfaceView = new GameSurfaceView(this);
setContentView(mGameSurfaceView);
//start the thread
new Thread(new GameThread()).start();
}
Handler myHandler = new Handler()
{
public void handleMessage(Message msg)
{
switch (msg.what)
{
case Activity01.REFRESH:
mGameSurfaceView.invalidate();
break;
}
super.handleMessage(msg);
}
};
class GameThread implements Runnable
{
public void run()
{
while (!Thread.currentThread().isInterrupted())
{
Message message = new Message();
message.what = Activity01.REFRESH;
//send message
Activity01.this.myHandler.sendMessage(message);
try {
Thread.sleep(100);
} catch (InterruptedException e) {
// TODO: handle exception
Thread.currentThread().interrupted();
}
}
}
}
public boolean onKeyUp(int keyCode, KeyEvent event)
{
switch (keyCode)
{
case KeyEvent.KEYCODE_DPAD_UP:
mGameSurfaceView.y-=3;
break;
case KeyEvent.KEYCODE_DPAD_DOWN:
mGameSurfaceView.y+=3;
break;
}
return true;
}
}

package com.gameview;

import android.R.drawable;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.Rect;
import android.graphics.RectF;
import android.util.Log;
import android.view.View;

public class GameView extends View {

int miCount = 0;
int y = 0;
public GameView(Context context) {
super(context);
// TODO Auto-generated constructor stub
}
public void onDraw(Canvas canvas)
{
if(miCount<100)
{
miCount++;
}
else
{
miCount = 0;
}
Paint mPaint = new Paint();
switch (miCount%4)
{
case 0:
mPaint.setColor(Color.BLUE);
break;
case 1:
mPaint.setColor(Color.GREEN);
break;
case 2:
mPaint.setColor(Color.RED);
break;
case 3:
mPaint.setColor(Color.YELLOW);
break;
default:
mPaint.setColor(Color.WHITE);
break;
}
//paint the rectangle
canvas.drawRect((500-80)/2, y, (500-80)/2+80, y+40, mPaint);
}
}

我们通过onDraw来绘制图，用invalidate的方法来实现界面的刷新，注意invalidate不能直接在进程中调用，因为它违背了单线程的模式：android的UI操作并不是线程安全的，并且这些操作必须在UI线程当中执行，因此android中最常用的方法是利用Handler来实现UI进程的更新