Android的“?colorPrimary"对比“?attr/colorPrimary"? [英] Android "?colorPrimary" vs "?attr/colorPrimary"?

问题描述

我找不到有关以下两者之间差异的任何信息:

I can't find any information about the differences between:

android:textColor="?attr/colorPrimary"

vs

android:textColor="?colorPrimary"

我已经读到?attr"表示当前主题中指定的属性值，但没有"attr"时，它给出的结果相同(=主题中定义的颜色).它的行为与其他属性相似吗?

I have read that "?attr" means attribute value specified in the current theme, but without "attr" it gives the same result (=color defined in my theme). It behaves similar with other attributes?

例如:

是android:background="?attr/selectableItemBackground" 等于android:background="?selectableItemBackground"吗?

​​这里被告知与众不同.

非常感谢.

推荐答案

好，我终于在文档中找到了

Ok, I have finally found in the docs:

由于系统资源工具知道在这种情况下需要属性资源，因此您无需显式声明类型(类型为android:attr/textColorSecondary)，可以排除attr类型.

Because the system resource tool knows that an attribute resource is expected in this context, you do not need to explicitly state the type (which would be ?android:attr/textColorSecondary)—you can exclude the attr type.

因此，我得出这样的结论:AppCompat库属性被视为自定义属性，因此，我们用问号将其指向而没有"android"关键字. "attr"是资源的类型，对于平台属性和自定义属性都是可选的(来自docs). Android文档

So, I deducted it's like this: the AppCompat library attributes are treated as custom attributes and as a result we point them by a question mark without "android" keyword. And "attr" is type of resource which is optional for both platform and custom attributes (from docs). Android documentation

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