跟随手指运动的小球或十字型

main.xml文件：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:id="@+id/root" />

主文件MoveBall.java：

package com.ucrobotics.moveball;
 
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 MoveBall extends Activity
{
        @Override
        public void onCreate(Bundle savedInstanceState)
        {
                super.onCreate(savedInstanceState);
                setContentView(R.layout.main);
                //获取布局文件中的LinearLayout容器
                LinearLayout root = (LinearLayout)findViewById(R.id.root);
                //创建DrawView组件
                final DrawView draw = new DrawView(this);
                //设置自定义组件的最大宽度、高度
                //draw.setMinimumWidth(300);
                //draw.setMinimumHeight(500);
                //为draw组件绑定Touch事件
                draw.setOnTouchListener(new OnTouchListener()
                {
                        @Override
                        public boolean onTouch(View arg0, MotionEvent event)
                        {
                                //修改draw组件的currentX、currentY两个属性
                                draw.currentX = event.getX();
                                draw.currentY = event.getY();
                                //通知draw组件重绘
                                draw.invalidate();
                                //返回true表明处理方法已经处理该事件
                                return true;
                        }               
                });
                root.addView(draw);
        }
}

绘制小球或十字型文件DrawView.java：

package com.ucrobotics.moveball;
 
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
{
        public float currentX = 40;
        public float currentY = 50;
        /**
         * @param context
         */
        public DrawView(Context context)
        {
                super(context);
                // TODO Auto-generated constructor stub
        }
        @Override
        public void onDraw (Canvas canvas)
        {
                super.onDraw(canvas);
                //创建画笔
                Paint p = new Paint();
                //设置画笔的颜色
                p.setColor(Color.RED);
 
                //绘制一个小圆（作为小球）
                //canvas.drawCircle(currentX , currentY , 15 , p);
 
                //绘制一个“十”字型
                canvas.drawLine(currentX-25, currentY, currentX+25, currentY, p); //“十”字型横线
                canvas.drawLine(currentX, currentY-25, currentX, currentY+25, p); //“十”字型竖线
        }
}

代码最后的绘制小球和“十”字型个任选一进行测试！

执行时会出现选定的图标，然后随着手指进行运动。

参考：www.eoeandroid.com/forum.php?mod=viewthread&tid=101780