如何定制自己的View

关于如何定制自己的View,查了相关的文档也看了一些例子，现在把自己的理解总结一下，和大家分享。
制定自己的View,一般要继承自某一类的View,然后完成构造方法，以及对onDraw()的重写，构造方法里面涉及到一些自定义的属性，自定义的属性在res/values下新建一个attrs.xml中申明，如下所示：

arrts.xml
<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name="MyView" >
    	<attr name="text_color" format="color" />
    	<attr name="text_size" format="dimension" />
    </declare-styleable >
</resources>

在构造方法中属性的引用格式是：属性集合名_属性名，如这里要引用text_color属性，则是R.stylebale.MyView_text_color
接下来的重点就是自定义自己的View，先上代码：

package com.lee.view;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Paint.Style;
import android.util.AttributeSet;
import android.view.View;

public class MyView extends View {
	private Paint myPaint;//画笔
	private static final String BLOG = "http://xueyilee.iteye.com";
	
	public MyView(Context context) {
		super(context);
		myPaint = new Paint();
	}

/*
Constructor that is called when inflating a view from XML. This is called when a view is being constructed from an XML file, supplying attributes that were specified in the XML file. This version uses a default style of 0, so the only attribute values applied are those in the Context's Theme and the given AttributeSet.xml布局文件有该View时就调用此构造方法,属性会传给attrs
*/	
	public MyView(Context context, AttributeSet attrs) {
		super(context, attrs);
		myPaint = new Paint();
		
		//获得TypedArray接口容器,通过它可以检索自定义的属性
		TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.MyView);
		
		//检索属性值，第二个参数是默认值，如果没有定义则返回默认值
		int textColor = ta.getColor(R.styleable.MyView_text_color, 0xff0000);
		float textSize = ta.getDimension(R.styleable.MyView_text_size, 30);
		
		myPaint.setColor(textColor);
		myPaint.setTextSize(textSize);
		ta.recycle();//这个回收方法一定不要忘了
	}
	
	/*当View渲染它的内容的时候调用此方法*/
	@Override
	protected void onDraw(Canvas canvas) {
		super.onDraw(canvas);
		myPaint.setStyle(Style.FILL);//设置填充
		myPaint.setAntiAlias(true);//消除锯齿
		canvas.drawCircle(50, 50, 30, myPaint);
		myPaint.setColor(Color.BLUE);
		canvas.drawText(BLOG, 20, 100, myPaint);
	}


}

接下来就是布局文件了。

main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 
	xmlns:android="http://schemas.android.com/apk/res/android"
        
//这个命名空间部分千万不要忘了，它是自定义属性前缀
	xmlns:lee="http://schemas.android.com/apk/res/com.lee.view"

	android:orientation="vertical"
	android:layout_width="match_parent"
	android:layout_height="match_parent"
    >

	<com.lee.view.MyView
		android:layout_width="match_parent"
		android:layout_height="wrap_content"
		lee:text_color="#00ff00"
		lee:text_size="20px"
		/>
			
</LinearLayout>

差不多就这么多了，下面是程序运行后的结果：