Android ViewModel (Kotlin)
February 27, 2019The ViewModel class is designed to store and manage UI-related data in a lifecycle conscious way. The ViewModel class allows data to survive configuration changes such as screen rotations.
dependencies {
def lifecycle_version = "2.0.0"
// ViewModel and LiveData
implementation "androidx.lifecycle:lifecycle-extensions:$lifecycle_version"
// alternatively - just ViewModel
implementation "androidx.lifecycle:lifecycle-viewmodel-ktx:$lifecycle_version"
// alternatively - just LiveData
implementation "androidx.lifecycle:lifecycle-livedata-ktx:$lifecycle_version"
kapt "androidx.lifecycle:lifecycle-compiler:$lifecycle_version"
// optional - Test helpers for LiveData
testImplementation "androidx.arch.core:core-testing:$lifecycle_version"
}
NOTE: One of my latest project seems to include androidx.lifecycle.*
libraries without explicitly importing them, perhaps some google libraries included them as depedencies.
Activity
class MainActivity : AppCompatActivity() {
private lateinit var viewModel: MainViewModel
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
viewModel = ViewModelProviders.of(this).get(MainViewModel::class.java)
}
}
ViewModel
class MainViewModel : ViewModel() {
internal var lastActiveFragmentTag: String? = null
}
NOTE: You might be interested to use Dagger2 with ViewModel.
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