无法使用数据绑定Android从ViewModel与XML通信

Question

I am trying to communicate with viewmodel from xml and vice versa using MVVM pattern. I have worked on databinding before and successfully worked with Live Data - Dagger - MVVM . Recently, I have tried to create a new project and since then I cannot track the response with XML and viewmodel. Neither the onClick from XML -> ViewModel nor the assigning value to the textview from View -> XML is working. But there is no crash or anything, just it is not working. I have added all associated files [ MainActivity, activity_main, viewModel, Dagger Module, build.gradle ]

I will really appreciate if anyone can tell me what is going wrong here.

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools">

<data>
    <variable
        name="viewmodel"
        type="aveek.com.vm.ui.home.MainActivityViewModel"/>
</data>
<android.support.constraint.ConstraintLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

 <TextView

        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@{viewmodel.balanceText}"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        android:clickable="true"
        android:onClick="@{() -> viewmodel.clickData()}"
        app:layout_constraintTop_toTopOf="parent" />
...
</layout>

MainActivity.kt

class MainActivity : AppCompatActivity(),LifecycleOwner {

@Inject
lateinit var binding : ActivityMainBinding

override fun onCreate(savedInstanceState: Bundle?) {
    AndroidInjection.inject(this)
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)
    binding.setLifecycleOwner(this) 
    with(binding){
        this.viewmodel?.let {
            it.balanceText.set( "Aveek testing")
            it.data.observe(this@MainActivity, Observer {
                Toast.makeText(this@MainActivity, "Data is now : $it", Toast.LENGTH_SHORT).show()
            })
           }
         }
       }

MainActivityViewModel.kt

class MainActivityViewModel : ViewModel() {
val data = MutableLiveData<Boolean>()
val balanceText = ObservableField<String>()
 fun clickData(){
    data.value = false
 }
}

MainActivityModule.kt

@Module
class  MainActivityModule{

/**
 * provides binding to  Main Activity from respective XML
 * @property viewModel
 * @property context
 * @return binding of the view
 */
@Provides
fun binding(context: MainActivity, viewModel : MainActivityViewModel) : 
ActivityMainBinding {
    val binding = DataBindingUtil.setContentView<ActivityMainBinding>(context, 
    R.layout.activity_main)
    binding.viewmodel = viewModel
    return binding
 }
}

build.gradle

apply plugin: 'com.android.application'

apply plugin: 'kotlin-android'

apply plugin: 'kotlin-android-extensions'

apply plugin: 'kotlin-kapt'

android {
   compileSdkVersion 27
   defaultConfig {
    applicationId "aveek.test"
    minSdkVersion 15
    targetSdkVersion 27
    versionCode 1
    versionName "1.0"
    testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    vectorDrawables.useSupportLibrary = true
   }
   dataBinding {
    enabled = true
   }
   buildTypes {
    release {
        minifyEnabled false
        proguardFiles getDefaultProguardFile('proguard-android.txt'), 
     'proguard-rules.pro'
    }
    }
    compileOptions {
     sourceCompatibility JavaVersion.VERSION_1_8
     targetCompatibility JavaVersion.VERSION_1_8
    }
   }

kapt {
  generateStubs = true
}

dependencies {
implementation fileTree(dir: 'libs', include: ['*.jar'])
implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
implementation 'com.android.support:appcompat-v7:27.1.1'
implementation 'com.android.support.constraint:constraint-layout:1.1.3'
implementation 'com.android.support:multidex:1.0.2'
implementation 'com.android.support:design:27.1.1'
implementation "android.arch.lifecycle:extensions:1.1.0"
//    annotationProcessor "android.arch.lifecycle:compiler:1.1.0"

kapt "com.android.databinding:compiler:$androidPluginVersion"

annotationProcessor "com.google.dagger:dagger-compiler:$daggerVersion"
annotationProcessor "com.google.dagger:dagger-android-processor:$daggerVersion"
kapt "com.google.dagger:dagger-compiler:$daggerVersion"
kapt "com.google.dagger:dagger-android-processor:$daggerVersion"


implementation "com.google.dagger:dagger:$daggerVersion"
implementation "com.google.dagger:dagger-android:$daggerVersion"
implementation "com.google.dagger:dagger-android-support:$daggerVersion"
kapt "com.google.dagger:dagger-compiler:$daggerVersion"

testImplementation 'junit:junit:4.12'
androidTestImplementation 'com.android.support.test:runner:1.0.2'
androidTestImplementation 'com.android.support.test.espresso:espresso- 
core:3.0.2'

}


ext{
    kotlin_version = '1.2.31'
    androidPluginVersion = '3.1.0'
    daggerVersion = '2.13'
}

Answer 1

您将无法使用任何生成的方法来将变量设置为绑定，因为除了ViewDataBinding之外没有通用的超类，因此您将被迫使用反射，或者可以使用便捷方法setVariable（）：

binding.setVariable(BR.viewModel, viewModel);

Answer 2

As I suspected, the problem is with Dagger injection. Maybe I have implemented in a wrong approach but the viewmodel is perfectly fine if running without DI.

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

    viewModel = ViewModelProviders.of(this).get(MainActivityViewModel::class.java)
    binding = DataBindingUtil.setContentView(this, R.layout.activity_main)
    binding.viewmodel = viewModel

    binding.setLifecycleOwner(this)
    mLifecycleRegistry = LifecycleRegistry(this).apply {
        markState(Lifecycle.State.CREATED)
    }
    with(binding){
        this.viewmodel?.let {
            it.balanceText.set( "Aveek testing")
            it.data.observe(this@MainActivity, Observer {
                Toast.makeText(this@MainActivity, "Data is now : $it", 
          Toast.LENGTH_SHORT).show()
            })
        }
    }
}

So, I have gone through the DI code and found out that in MainActivity.onCreate() I was doing this

AndroidInjection.inject(this)
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)

which basically overriding the databinding behaviour. So I have updated the code like this

AndroidInjection.inject(this)
super.onCreate(savedInstanceState)
//setContentView(R.layout.activity_main)
// and initiated binding here as injecting binding from module before setting content won't be effective
val binding = DataBindingUtil.setContentView<ActivityMainBinding>(this, R.layout.activity_main)

And removed

//    @Inject
//    lateinit var binding : ActivityMainBinding

Now it works perfectly fine..