Android-自定义View

自定义一个跟随手指的小球

DrawView.java文件

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

public class DrawView extends View{
 
    
    public float currentX=40;
    public float currentY=50;
    
    Paint p=new Paint();//定义画笔
    
    public DrawView(Context context) {
        super(context);
        
    }
    //构造器一定要有否则报错
     public DrawView(Context context, AttributeSet attrs){  
            super(context, attrs);  
        }  
    
    @Override
    protected void onDraw(Canvas canvas) {
        
        super.onDraw(canvas);
        p.setColor(Color.RED);
        canvas.drawCircle(currentX, currentY, 15, p);//画圆形
        
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        
        currentX=event.getX();
        currentY=event.getY();
        
        //通知组件重绘制
        this.invalidate(); 
        return true;
    }


    
}

layout.xml加入

 <com.layer.study3027.DrawView 
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        
        
        
        />