挥动的小球

编写时遇到的问题：声明int变量时没有声明public，在重写ondraw方法时。没有继承，并且没有canvas；布局时Lineration写在了外面；重绘的语句不会写；

第一个文件：

package com.android.test;

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 x;

  public  float y;

 public DrawView(Context context) {

  super(context);

  // TODO Auto-generated constructor stub

 }

 public void onDraw(Canvas canvas){

  super.onDraw(canvas);

  Paint paint =new Paint();

  paint.setColor(Color.GREEN);

  canvas.drawCircle(x,y, 15, paint);

 

 }

}

第二个文件：

package com.android.test;

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 MoveBallActivity extends Activity {

    /** Called when the activity is first created. */

    @Override

    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.main);

   

    LinearLayout layout =(LinearLayout)findViewById(R.id.root);

    final DrawView drawView =new DrawView(this);

    drawView.setMinimumHeight(400);

    drawView.setMinimumWidth(400);

    drawView.setOnTouchListener(new OnTouchListener() {

  

  @Override

  public boolean onTouch(View v, MotionEvent event) {

   drawView.x= event.getX();

   drawView.y= event.getY();

     drawView.invalidate();

   return true;

  }

 });

    layout.addView(drawView);

}

}