多個類定義attr屬性重複的問題:Attribute "xxx" has already been defined

如果從單獨開發app的話，可能不會遇到多個自定義類的attribute 的名字重複的問題。但是如果是團隊合作開發的話，可能會碰到這樣的問題，A和B自定義的兩個類都用了同一個名字來定義屬性，這時系統會報出警告，Attribute "xxx" has already been defined. A和B又都不想修改自己的名字，這時就很頭痛。

下面舉個例子，在values文件夾下定義一個上面的attrs.xml的文件，eclipse即會報錯：Attribute "icon" has already been defined。因爲在PreferenceHeader, Preference兩個屬性集裏定義了兩個相同的屬性。

<? xml version = "1.0" encoding = "utf-8" ?>
< resources >
     < declare-styleable name= "PreferenceHeader" >
        <!-- Identifier value for the header. -->
        < attr name= "id" format = "integer"/>
        < attr name= "icon" format = "integer" />
        <!-- The fragment that is displayed when the user selects this item. -->
    </declare-styleable >
    < declare-styleable name= "Preference" >
        < attr name= "icon" format = "integer" />
        <!-- The key to store the Preference value. -->
        < attr name= "key" format = "string" />
    </declare-styleable >
</ resources >

解決方案：

1.在xml文件裏前面先聲明屬性

2.然後在屬性集合裏引用聲明的屬性即可。

以上面的文件爲例來修改，如下：

<? xml version = "1.0" encoding = "utf-8" ?>
< resources >
     < attr name = "icon" format = "integer" />
     < declare-styleable name= "PreferenceHeader" >
        <!-- Identifier value for the header. -->
        < attr name= "id" format = "integer"/>
        < attr name= "icon" />
        <!-- The fragment that is displayed when the user selects this item. -->
    </declare-styleable >
    < declare-styleable name= "Preference" >
        < attr name= "icon"  />
        <!-- The key to store the Preference value. -->
        < attr name= "key" format = "string" />
    </declare-styleable >
</ resources >