Unresolved reference for synthetic view when layout is in library module

Question

using Kotlin 1.20.20 (not that it matters, older versions behaves the same)

When layout is in separate library module Android Studio has no problem finding and refer

Answer 1

The solution is far simpler than imagined, Kotlin synthetic sugars are a part of Kotlin Android Extensions and you just have to apply the plugin manually (Android Studio applies this automatically only to application modules):

Add the following to your library / feature module's build Gradle:

apply plugin: 'kotlin-android-extensions'

Now enjoy Kotlin synthetic sugars in your Kotlin code! ;)

Answer 2

My scenario was : I needed base class (from lib) view references in child classes (app module) and had minimum number of view references from Library Module's base classes.

I would say, it's kind a fix and not a solution.

Solution #1 Get a view reference from Base class

//lib module snippet
import kotlinx.android.synthetic.main.view_user_input.*

class LibModuleBaseActivity : AppCompatActivity() {

   override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.view_user_input)
   }

    protected val vFirstName: TextView by lazy { tvFirstName }
    ...........
}


//app module snippet
class AppModuleActivity : LibModuleBaseActivity() {

    fun setUserDetails(name: String) {
        vFirstName.text = name
    }
}

Solution #2 Get the task done by Base Class

//lib module snippet
import kotlinx.android.synthetic.main.view_user_input.*

class LibModuleBaseActivity : AppCompatActivity() {
    protected fun setUserDetails(name: String) {
        tvFirstName.text = name
    }
    ...........
}


//app module snippet
class AppModuleActivity : LibModuleBaseActivity() {
    ............
    setUserDetails("user_name")
}

Note: This works only if you are inheriting from lib module and where your Base class is inflating views.

Answer 3

Update:

Synthetic view references have been deprecated and will not be supported in the future.

The current recommended solution is to use ViewBinding (or wait for Jetpack Compose)

Original Answer:

One way to solve this is to create an "alias" property that can be consumed from other modules:

// SyntheticExports.kt
package com.example.synthetic.exported

import kotlinx.android.synthetic.main.layout_in_library.*

inline val Activity.exported_text_view get() = text_view

Then on the other module:

// MainActivity.kt
import com.example.synthetic.exported.exported_text_view

exported_text_view.text = "example"

That works for us. Have to create different extensions for view, fragment, etc. It's a bit tedious to have to do them manually but this is the simplest workaround we found.

Extra: This is also a decent method to export synthetic extensions as part of a public library too, not just in an internal module.

Answer 4

None of the above answers actually helped me . Add both these plugins in your library module's build.gradle file on top :

apply plugin: 'kotlin-android-extensions'
apply plugin: 'kotlin-android'

This should solve the issue .