android - "@+id/idname"格式的@在android中是什么意思？

Question

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他们说:

The at sign (@) is required when you're referring to any resource object from XML. It is followed by the resource type (id in this case), a slash, then the resource name (edit_message).

不太明白@是什么意思，谁能给个更具体的解释？

Answer 1

如果 ID 尚未创建，则 + 将创建它。只有在第一次引用该 ID 时才需要它。

来自文档:

The plus sign (+) before the resource type is needed only when you're defining a resource ID for the first time. When you compile the app, the SDK tools use the ID name to create a new resource ID in your project's gen/R.java file that refers to the EditText element. With the resource ID declared once this way, other references to the ID do not need the plus sign.

如文档所述，@ 符号表示您正在引用 xml 资源。例如:@string/edit_message 表示您正在尝试引用一个在 xml 文件中定义了 id edit_message 的字符串。