<?xml version="1.0" encoding="utf-8"?>

<resources>

    <declare-styleable name="MyCircle">

        <attr name="radius" format="integer"/>

        <attr name="mycolor" format="reference|color"/>

    </declare-styleable>

</resources>

package com.ch.myviews;

import com.ch.myviewattr.R;

import android.content.Context;

import android.content.res.TypedArray;

import android.graphics.Canvas;

import android.graphics.Color;

import android.graphics.Paint;

import android.util.AttributeSet;

import android.view.View;

public class MyCircle extends View {

    private Paint paint;

    private int radius;

    public MyCircle(Context context, AttributeSet attrs) {

        super(context, attrs);

        // TODO Auto-generated constructor stub

        //获得自定义的属性，即获得自定义的半径

        TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.MyCircle);

        radius = ta.getInt(R.styleable.MyCircle_radius, 0);

    }

    //绘制的方法

    @Override

    protected void onDraw(Canvas canvas) {

        // TODO Auto-generated method stub

        paint = new Paint();

        paint.setColor(Color.RED);

//        canvas.drawColor(Color.BLACK);

        canvas.drawCircle(getMeasuredWidth()/2, getMeasuredHeight()/2, radius, paint);

        super.onDraw(canvas);

    }

}

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

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

    xmlns:myattr="http://schemas.android.com/apk/res/com.ch.myviewattr"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    tools:context=".MainActivity" >

    <com.ch.myviews.MyCircle

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_centerHorizontal="true"

        android:layout_centerVertical="true"

        myattr:radius="200"

        />

</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>

<resources>

    <declare-styleable name="MyCircle">

        <attr name="radius" format="integer"/>

        <attr name="mycolor" format="reference|color"/>

    </declare-styleable>

</resources>

package com.ch.myviews;

import com.ch.myviewattr.R;

import android.content.Context;

import android.content.res.TypedArray;

import android.graphics.Canvas;

import android.graphics.Color;

import android.graphics.Paint;

import android.util.AttributeSet;

import android.view.View;

public class MyCircle extends View {

    private Paint paint;

    private int radius;

    private final static String NAMESPACE = "aaa1407a";

    public MyCircle(Context context, AttributeSet attrs) {

        super(context, attrs);

        // TODO Auto-generated constructor stub

        //获得自定义的属性，即获得自定义的半径

        radius = attrs.getAttributeIntValue(NAMESPACE, "radius", 0);

    }

    //绘制的方法

    @Override

    protected void onDraw(Canvas canvas) {

        // TODO Auto-generated method stub

        paint = new Paint();

        paint.setColor(Color.RED);

//        canvas.drawColor(Color.BLACK);

        canvas.drawCircle(getMeasuredWidth()/2, getMeasuredHeight()/2, radius, paint);

        super.onDraw(canvas);

    }

}

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

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

    xmlns:myattr="aaa1407a"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    tools:context=".MainActivity" >

    <com.ch.myviews.MyCircle

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_centerHorizontal="true"

        android:layout_centerVertical="true"

        myattr:radius="200"

        />

</RelativeLayout>