Reference attribute enum value

问题:

Is it possible to reference an enum value when supplying style parameters?
For example, we can do:

<!-- layouts.xml -->
<TextView
    android:text="@string/str" />

<!-- values.xml -->
<item type="string" name="str">hi</item>

This works fine with strings, integers, dimensions and so on but I need to reference an enum value - for example the visibility attribute. I'm looking for something like:

<!-- layouts.xml -->
<TextView
    android:visibility="@????/viz" />

<!-- values.xml -->
<item type="?????" name="viz">gone</item>

visibility is only an example - it could be any other enum based attribute.

The only workaround I have found so far is by using styles

<!-- layouts.xml -->
<TextView
    android:style="@styles/theStyle" />

<!-- styles.xml -->
<style name="theStyle">
    <item name="android:visibility">gone</item>
</style>

But this is somehow restrictive because it becomes increasingly complicated if you need to use real styles with the TextViews and this special style which is only used to control a single attribute.

Another option would be if there is a way to reference individual style items. Something like:

<TextView
    android:visibility="@styles/theStyle/visibility" />

But I think that the above is even less likely to be possible.

回答1:

Each enum is actually a set of named integers. For example, visibility attribute is declared as follows:

<attr name="visibility">
    <enum name="visible" value="0" />
    <enum name="invisible" value="1" />
    <enum name="gone" value="2" />
</attr>

So you can reference to enum item directly by its value. Something like this:

<!-- values.xml -->
<item name="viz" type="integer">1</item>

<!-- layouts.xml -->
<TextView
    android:visibility="@integer/viz"/>

I just checked it on my phone and it works well.