Android Databinding in Sub-module

Question

I have an application module, let's say "Test". The "Test" module depends on a sub-module B. Both enable databinding. In library module B, I create a simple activity using databinding, its purpose is for reusability, for example: I can create a base Login screen and use it in many apps later. Below is sample code in Package B.

package com.test.packageb

      open class MainActivity : AppCompatActivity() {

        lateinit var binding : ActivityMainBinding

        override fun onCreate(savedInstanceState: Bundle?) {
            super.onCreate(savedInstanceState)
            binding = DataBindingUtil.setContentView(this, R.layout.activity_main)
        }
    }

and then in "Test" module, I can just simply inherit MainActivity class to do customize things, like this:

class MainActivity1 : MainActivity(){

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
    }

    fun doSomething(){
        binding.rootLayout.setBackgroundResource(R.color.colorPrimary)
    }
}

However, when I try to run "Test" application, I got this error

Error:(17, 9) Cannot access class 'com.test.packageb.databinding.ActivityMainBinding'. Check your module classpath for missing or conflicting dependencies
Error:(17, 17) Unresolved reference: rootLayout

What did I miss? Is there anything else need to be implemented?

Test app build.gradle

apply plugin: 'com.android.application'

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

android {
    compileSdkVersion 26
    buildToolsVersion "26.0.1"
    defaultConfig {
        applicationId "com.test.testapplication"
        minSdkVersion 15
        targetSdkVersion 26
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }

    dataBinding{
        enabled true
    }

    buildTypes {
        debug {

        }
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    kapt 'com.android.databinding:compiler:3.0.0-beta4'
    implementation fileTree(include: ['*.jar'], dir: 'libs')
    implementation 'com.android.support:appcompat-v7:26.0.2'
    implementation 'com.android.support.constraint:constraint-layout:1.0.2'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation('com.android.support.test.espresso:espresso-core:3.0.1', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jre7:$kotlin_version"
    implementation project(':packageb')
}

Package B build.gradle

apply plugin: 'com.android.library'
apply plugin: 'kotlin-android'
apply plugin: 'kotlin-android-extensions'
apply plugin: 'kotlin-kapt'
android {
    compileSdkVersion 26
    buildToolsVersion "26.0.1"


    defaultConfig {
        minSdkVersion 15
        targetSdkVersion 26
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"

    }
    dataBinding{
        enabled true
    }
    buildTypes {
        debug {
            minifyEnabled false
        }
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }

}

dependencies {
    kapt 'com.android.databinding:compiler:3.0.0-beta4'
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:26.0.2'
    implementation 'com.android.support.constraint:constraint-layout:1.0.2'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation('com.android.support.test.espresso:espresso-core:3.0.1', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jre7:$kotlin_version"
}

Answer 1

Not sure if the issue is relevant to you but I managed to find some kind of the solution.

To make it work base class should have generic

class A<BINDING extends ViewDataBinding> {
    protected ABinding binding;

    void init(){
        binding = (ABinding) DataBindingUtil.setContentView(this, R.layout.a);
    }
}

and pass the same binding to the child class from the submodule

class B<ABinding> {
    // you can use instance in this class
}

The main problem here that you can't drastically change the UI, only hiding existing elements or add new at runtime. But I suppose in such case easier create a totally new class.