“@id/"之间的区别和“@+id/"在安卓中 [英] Difference between "@id/" and "@+id/" in Android

问题描述

@id/ 和 @+id/ 有什么区别?

在 @+id/ 中，加号 + 指示创建一个新的资源名称并添加到 R 中.java 文件，但是 @id/ 呢?来自 ID:引用Android资源ID时，不需要加号，但必须添加android包命名空间，如下所示:

In @+id/ the plus symbol + instructs to create a new resource name and add in to the R.java file but what about @id/? From the documentation of ID: when referencing an Android resource ID, you do not need the plus symbol, but must add the android package namespace, like so:

android:id="@android:id/list"

但是在下面的图片中，Eclipse 不建议使用任何类型的 @android:id/.

But in the image below Eclipse doesn't suggest any kind of @android:id/.

@id/ 和 @android:id/ 是否相同?

推荐答案

你参考了Android资源，Android系统中已经定义好了，@android:id/.. 而要访问您在项目中定义/创建的资源，您可以使用 @id/..

you refer to Android resources , which are already defined in Android system, with @android:id/.. while to access resources that you have defined/created in your project, you use @id/..

更多信息

根据你在聊天中的澄清，你说你有这样的问题:

As per your clarifications in the chat, you said you have a problem like this :

如果我们使用 android:id="@id/layout_item_id" 它不起作用.相反 @+id/ 有效，那么这里有什么区别?这就是我最初的问题.

If we use android:id="@id/layout_item_id" it doesn't work. Instead @+id/ works so what's the difference here? And that was my original question.

嗯，这取决于上下文，当您使用 android:id 的 XML 属性时，您将指定一个新的 id，并指示解析器(或称其为builder) 在 R.java 中创建一个新条目，因此你必须包含一个 + 符号.

Well, it depends on the context, when you're using the XML attribute of android:id, then you're specifying a new id, and are instructing the parser (or call it the builder) to create a new entry in R.java, thus you have to include a + sign.

而在另一种情况下，例如 android:layout_below="@id/myTextView" ，您指的是已创建的 id，因此解析器将其链接到已创建的 id在 R.java.

While in the other case, like android:layout_below="@id/myTextView" , you're referring to an id that has already been created, so parser links this to the already created id in R.java.

再次了解更多信息

正如您在聊天中所说，请注意 android:layout_below="@id/myTextView" 将无法识别具有 id myTextView 的元素，如果它写在您在其中使用它的元素.

As you said in your chat, note that android:layout_below="@id/myTextView" won't recognize an element with id myTextViewif it is written after the element you're using it in.

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