TL;DR:
This line compiles:
int resid = android.R.layout.preference_category;
But this line does not:
int resid = android.R.layout.preference;
The error is "cannot find symbol variable preference". But both resources are clearly available in the Sdk\platforms\android-28\data\res\layout directory!
Why does this happen?
Background
I can navigate (in the IDE) to the preference_category resource, and sure enough, the preference.xml layout is right next to it, along with about a thousand other layouts that, similarly, will not compile.
My build.gradle (excerpt):
compileSdkVersion 28
defaultConfig {
minSdkVersion 18
targetSdkVersion 26
}
I recently switched my app over to AndroidX. For the most part, everything went smoothly, except I noticed my preferences had new visual styles. I wouldn't care, except that I had "subclassed" preference.xml by copying the original Android layout, making a trivial change, and then specifying that layout in my prefs.xml, e.g.:
...
<androidx.preference.CheckBoxPreference
android:key="@string/pref_audio"
android:title="Audio"
android:defaultValue="false"
android:layout="@layout/my_custom_preference"
/>
...
Preferences that I've handled in this way still look like they used to -- the way they looked before I switched to AndroidX. But all the other preferences now look drastically different.
I went back to the API level 28 folder, and checked the contents of Android's original preference.xml, to see if it had changed (since I originally copied/subclassed it). It has not! Yet, the styles of the preferences have changed.
To troubleshoot, I tried to verify that android.R.layout.preference was actually pointing to the resource I was looking at, which led me to the above mentioned compilation error.
