Android跟随手指运动的小球 适合新手的很好的Demo

为了实现一个跟随手指的小球，我们运用自定义的View组件
；这个UI组件将会在指定的位置绘制一个小球 ，这个位置可以动态改变 。当用户通过手指在屏幕上拖动时，程序监听这个手指动作，并把手指动作位置传给自定义UI组件，并通知组件重绘。

自定义UI组件 DrawView.java：

package yuhee.mars;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.view.View;

public class DrawView  extends View{
        
        /* (non-Javadoc)
         * @see android.view.View#onDraw(android.graphics.Canvas)
         */
        

        public float currentx = 40 ;
        public  float currenty = 50 ;
        /**
         * 
         * @param context
         */
        public DrawView(Context context) {
                super(context);
                // TODO Auto-generated constructor stub
        }
        @Override
        protected void onDraw(Canvas canvas) {
                // TODO Auto-generated method stub
                super.onDraw(canvas);
                //创建画笔 ;
                Paint p = new Paint() ;
                p.setColor(Color.GREEN) ;
                //绘制一个小球 ；
                canvas.drawCircle(currentx, currenty, 15, p) ;
    }
        }

下面是该应用的Activity类：

package yuhee.mars;

import android.app.Activity;
import android.os.Bundle;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.widget.LinearLayout;

public class Activity_06Activity extends Activity {
    /** Called when the activity is first created. */
    @Override
            public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        LinearLayout main = (LinearLayout)findViewById(R.id.root) ;
        final DrawView draw = new DrawView(this) ;
        draw.setMinimumWidth(300) ;
        draw.setMinimumHeight(500) ;
        draw.setOnTouchListener(new OnTouchListener()
        {

                        @Override
                        public boolean onTouch(View arg0, MotionEvent event) {
                                // TODO Auto-generated method stub
                                draw.currentx = event.getX() ;
                                draw.currenty = event.getY() ;
                                //通知Draw组件重绘 ;
                                draw.invalidate() ;
                                return true ;
                                
                        }
                
        }) ;
        main.addView(draw) ;
        }
}

看下效果图：欢迎各位拍砖