自定义view 读取 属性No resource identifier found for attribute

首先看一个错误

error: No resource identifier found for attribute '' in package

这个错误主要原因是

属性不存在(注意属性区分大小写)

其中xmlns必须写, 

<com.package.name.view.LinearLayoutWithLine
xmlns:app="http://schemas.android.com/apk/res-auto"
......
app:paddingLineLeft="1dip"

不写的话读取不到属性值，如下所示 error虽然编译成功,但是取不到值

<com.package.name.view.LinearLayoutWithLine
......
paddingLineLeft="1dip"

还需要注意一个问题，如果命名空间采用老式写法

<com.package.name.view.LinearLayoutWithLine
xmlns:app="http://schemas.android.com/apk/res/com.package.name"
......
app:paddingLineLeft="1dip"

xmlns最后面是res/app的包名. 而不是v自定义的iew所在的package的路径

xmlns:app="http://schemas.android.com/apk/res/com.package.name.view"

这么写是错误的

。。。。。

完整用法如下（注意查看一下顺序）

<declare-styleable name="LinearLayoutWithLine">
<!-- 线的颜色 -->
<attr name="lineColor" format="color"/>
<attr name="paddingLineLeft" format="dimension"/>
<attr name="paddingLineTop" format="dimension"/>
<attr name="paddingLineRight" format="dimension"/>
<attr name="paddingLineBottom" format="dimension"/>
</declare-styleable>

TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.LinearLayoutWithLine);
paddlingLineLeft = (int) ta.getDimension(R.styleable.LinearLayoutWithLine_paddingLineLeft, getPaddingLeft());
paddlingLineTop = (int) ta.getDimension(R.styleable.LinearLayoutWithLine_paddingLineTop, getPaddingTop());
paddlingLineRight = (int) ta.getDimension(R.styleable.LinearLayoutWithLine_paddingLineRight, getPaddingRight());
paddlingLineBottom = (int) ta.getDimension(R.styleable.LinearLayoutWithLine_paddingLineBottom, getPaddingBottom());
ta.recycle();

ta.getDimension 的第一个参数是下标 
public static final int LinearLayoutWithLine_lineColor = 0;
public static final int LinearLayoutWithLine_paddingLineLeft = 1;
public static final int LinearLayoutWithLine_paddingLineTop = 2;

值按照declare-styleable定义的LinearLayoutWithLine中的顺序累加的

所以 取值也可以写成下列

TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.LinearLayoutWithLine);
paddlingLineLeft = (int) ta.getDimension(1, getPaddingLeft());
paddlingLineTop = (int) ta.getDimension(2, getPaddingTop());
paddlingLineRight = (int) ta.getDimension(3, getPaddingRight());
paddlingLineBottom = (int) ta.getDimension(4, getPaddingBottom());
ta.recycle();