android学习之通过handler更新UI的例子

通过handler来更新UI：

package com.myandroid.handler;

import android.app.Activity;

import android.os.Bundle;

import android.app.Activity;

import android.content.Context;

import android.graphics.Canvas;

import android.graphics.Color;

import android.graphics.Paint;

import android.os.Bundle;

import android.os.Handler;

import android.view.View;

public class HandlerViewActivity extends Activity {

    private MyView myView;

    private Handler mHandler;

    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        myView = new MyView(this);

        mHandler = new Handler();

        mHandler.post(new Runnable() {

            @Override

            public void run() {

                myView.invalidate();

                mHandler.postDelayed(this, 5);

            }

        });www.2cto.com

        setContentView(myView);

    }

    class MyView extends View {

        private float x = 0f;

        public MyView(Context context) {

            super(context);

        }

        protected void onDraw(Canvas canvas) {

            super.onDraw(canvas);

            x += 1;

            Paint mPaint = new Paint();

            mPaint.setColor(Color.BLUE);

            canvas.drawRect(x, 40, x + 20, 48, mPaint);

            canvas.drawRect(x, 54, x + 20, 62, mPaint);

            canvas.drawCircle(x+10, 51, 6, mPaint);

            canvas.drawRect(x+10, 50, x + 20, 52, mPaint);

           

            mPaint.setColor(Color.RED);

            canvas.drawRect(x, 80, x + 20, 88, mPaint);

            canvas.drawRect(x, 94, x + 20, 102, mPaint);

            canvas.drawCircle(x+10, 91, 6, mPaint);

            canvas.drawRect(x+10, 90, x + 20, 92, mPaint);

           

            mPaint.setColor(Color.YELLOW);

            canvas.drawRect(x, 120, x + 20, 128, mPaint);

            canvas.drawRect(x, 134, x + 20, 142, mPaint);

            canvas.drawCircle(x+10, 131, 6, mPaint);

            canvas.drawRect(x+10, 130, x + 20, 132, mPaint);

           

            mPaint.setColor(Color.GREEN);

            canvas.drawRect(x, 160, x + 20, 168, mPaint);

            canvas.drawRect(x, 174, x + 20, 182, mPaint);

            canvas.drawCircle(x+10, 171, 6, mPaint);

            canvas.drawRect(x+10, 170, x + 20, 172, mPaint);

           

        }

    }

}

运行起来后看到有4个小坦克从左向右移动：