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