跟随手指的小球实现

文件是wlw.com然后建立RrawView.java文件

RrawView.java代码如下：

package com.example.wlw.com;
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 = 300;
     public float currentY = 500;
      
     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);
      Paint p = new Paint();
      p.setColor(Color.RED);
      canvas.drawCircle(currentX, currentY, 15, p);
     }
      
      
    }

MainActivity.java代码如下：

package com.example.wlw.com;

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;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_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 v, MotionEvent event) {
            draw.currentX = event.getX();
            draw.currentY = event.getY();
            draw.invalidate();
            return true;
           }
          });
             main.addView(draw);
         }
          
        }

acticity_main.xml代码如下：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  

    xmlns:tools="http://schemas.android.com/tools"  

    android:layout_width="fill_parent"

    android:layout_height="fill_parent"

    android:orientation="vertical"  

    android:background="#99FFCC"

    android:id="@+id/root">
       

    </LinearLayout>  

最后运行截图：