Data-Binding fails with "couldn't make a guess"

Question

Since the update to Android Studio 3.2.0 I face the following issue:

Execution failed for task ':mobile:dataBindingGenBaseClassesDebug'.

> couldn't make a guess for com.ACME.database.model.Order

also seen this answer, which hints for that "package-names must start with a lower-case letter".

... it seems alike, as if this variable assignment would be the cause:

<data class=".databinding.OrderFragmentBinding">
    <variable name="order" type="com.ACME.database.model.Order"/>
    ...
</data>

found: New data binding compiler for binding classes, which does not explain the change in behavior.

Q: are such assignments also affected by that naming convention? I mean, is there any chance (beside changing the uppercase package-name) to make that data-binding v2 "guess" work out?

Answer 1

A case where you will run into this error:

<data>
    <variable
        name="something"
        type=""/>
</data>

Empty type or undefined Type

Answer 2

Its because of your class name or package name which use databinding. These classes( which use databinding) has to started with capital letter and packages started with lowercase.

Answer 3

Had a similar problem. Solved by renaming the data class by starting with capital letters.

Answer 4

these settings in the gradle.properties do enable the androidx data-binding compiler:

android.databinding.enableV2 = false
android.enableExperimentalFeatureDatabinding = true

one can see that by the fetched package:

Download https://dl.google.com/dl/android/maven2/androidx/databinding/databinding-compiler/3.2.0/databinding-compiler-3.2.0.pom
Download https://dl.google.com/dl/android/maven2/androidx/databinding/databinding-compiler/3.2.0/databinding-compiler-3.2.0.jar

and it complains:

WARNING: The option setting 'android.databinding.enableV2=false' is experimental and unsupported.
The current default is 'true'

WARNING: The option setting 'android.enableExperimentalFeatureDatabinding=true' is experimental and unsupported.
The current default is 'false'

most likely androidx.fragment.app.Fragment instead of android.support.v4.app.Fragment would be required, in order to data-bind a Fragment with the default v2 data-binding compiler. this is also just a temporary solution - but still better than to revert to the v1 data-binding compiler.

---

Update:

Since com.android.tools.build:gradle:3.5.0 the above workaround does not work anymore; One has to refactor the XML files. It works best when not adding any class="" attribute into the <data /> tag - and also adding this tag into any existing <layout> tag. Duplicate id on data-bound <include> tags may also prevent the generation (the id has to be set on the <include> tag, not in the included layout).