问题：xml中使用自定义的类的时候，出现了XML file line #10: Binary XML file line #10: Error inflating class com.ui.demo.custom.DrawView异常。

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="com.ui.demo.custom.CustomView">

 <com.ui.demo.custom.DrawView
    android:id="@+id/test"
     android:layout_width="match_parent"
     android:layout_height="match_parent"/>
</LinearLayout>

package com.ui.demo.custom;

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

/**
 * <p>
 * Description:
 * </p>
 *
 * @author dailei
 * @version V1.0.0
 * @className DrawView
 * @date 2016/6/7
 */
public class DrawView extends View
{
    public float currentX = 40;
    public float currentY = 50;

    Paint p = new Paint();

    public DrawView(Context context)
    {
        super(context);
    }

//    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);
    }

    @Override public boolean onTouchEvent(MotionEvent event)
    {
        currentX = event.getX();
        currentY = event.getY();
        invalidate();  //通知当前组件重新绘自己
        return true;
    }
}