Move lifecycle logic to base classes

hichamboushaba · Oct 30, 2021 · 346d0f9 · 346d0f9
1 parent 58f77f2
commit 346d0f9
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Showing 4 changed files with 56 additions and 33 deletions.
diff --git a/app/src/main/java/com/hicham/flowlifecycle/BaseFragment.kt b/app/src/main/java/com/hicham/flowlifecycle/BaseFragment.kt
@@ -0,0 +1,16 @@
+package com.hicham.flowlifecycle
+
+import android.os.Bundle
+import android.view.View
+import androidx.annotation.LayoutRes
+import androidx.fragment.app.Fragment
+
+abstract class BaseFragment<T : BaseViewModel>(@LayoutRes contentLayoutId: Int) :
+    Fragment(contentLayoutId) {
+    protected abstract val viewModel: T
+
+    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
+        super.onViewCreated(view, savedInstanceState)
+        viewModel.startObservingLifecycle(viewLifecycleOwner)
+    }
+}
diff --git a/app/src/main/java/com/hicham/flowlifecycle/BaseViewModel.kt b/app/src/main/java/com/hicham/flowlifecycle/BaseViewModel.kt
@@ -0,0 +1,37 @@
+package com.hicham.flowlifecycle
+
+import android.app.Application
+import androidx.lifecycle.AndroidViewModel
+import androidx.lifecycle.Lifecycle
+import androidx.lifecycle.LifecycleEventObserver
+import androidx.lifecycle.LifecycleOwner
+import kotlinx.coroutines.channels.BufferOverflow
+import kotlinx.coroutines.flow.*
+
+open class BaseViewModel(application: Application): AndroidViewModel(application) {
+    private val lifeCycleState = MutableSharedFlow<Lifecycle.State>(
+        replay = 1,
+        onBufferOverflow = BufferOverflow.DROP_OLDEST
+    )
+
+    private val lifecycleObserver = object : LifecycleEventObserver {
+        override fun onStateChanged(source: LifecycleOwner, event: Lifecycle.Event) {
+            lifeCycleState.tryEmit(source.lifecycle.currentState)
+            if (source.lifecycle.currentState == Lifecycle.State.DESTROYED) {
+                source.lifecycle.removeObserver(this)
+            }
+        }
+    }
+
+    fun startObservingLifecycle(lifecycleOwner: LifecycleOwner) {
+        lifecycleOwner.lifecycle.addObserver(lifecycleObserver)
+    }
+
+    protected fun <T> Flow<T>.whenAtLeast(requiredState: Lifecycle.State): Flow<T> {
+        return lifeCycleState.map { state -> state.isAtLeast(requiredState) }
+            .distinctUntilChanged()
+            .flatMapLatest {
+                if (it) this else emptyFlow()
+            }
+    }
+}
diff --git a/app/src/main/java/com/hicham/flowlifecycle/MainFragment.kt b/app/src/main/java/com/hicham/flowlifecycle/MainFragment.kt
@@ -6,15 +6,14 @@ import android.os.Bundle
 import android.view.View
 import androidx.activity.result.contract.ActivityResultContracts
 import androidx.core.view.isVisible
-import androidx.fragment.app.Fragment
 import androidx.fragment.app.viewModels
 import androidx.lifecycle.lifecycleScope
 import com.hicham.flowlifecycle.databinding.FragmentMainBinding
 import kotlinx.coroutines.flow.launchIn
 import kotlinx.coroutines.flow.onEach
 
-class MainFragment : Fragment(R.layout.fragment_main) {
-    private val viewModel: MainViewModel by viewModels()
+class MainFragment : BaseFragment<MainViewModel>(R.layout.fragment_main) {
+    override val viewModel: MainViewModel by viewModels()
 
     private val requestPermissionLauncher =
         registerForActivityResult(
@@ -29,13 +28,10 @@ class MainFragment : Fragment(R.layout.fragment_main) {
 
     override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
         super.onViewCreated(view, savedInstanceState)
-        viewModel.startObservingLifecycle(viewLifecycleOwner)
-
         val binding = FragmentMainBinding.bind(view)
 
         val hasLocationPermission =
             requireContext().checkSelfPermission(Manifest.permission.ACCESS_FINE_LOCATION) == PERMISSION_GRANTED
-
         if (hasLocationPermission) {
             viewModel.onLocationPermissionGranted()
         } else {

diff --git a/app/src/main/java/com/hicham/flowlifecycle/MainViewModel.kt b/app/src/main/java/com/hicham/flowlifecycle/MainViewModel.kt
@@ -6,26 +6,12 @@ import androidx.lifecycle.*
 import kotlinx.coroutines.channels.BufferOverflow
 import kotlinx.coroutines.flow.*
 
-class MainViewModel(application: Application) : AndroidViewModel(application) {
+class MainViewModel(application: Application) : BaseViewModel(application) {
     private val locationObserver = LocationObserver(application)
     private val api: FakeApi = FakeApi()
 
     private val hasLocationPermission = MutableStateFlow(false)
 
-    private val lifeCycleState = MutableSharedFlow<Lifecycle.State>(
-        replay = 1,
-        onBufferOverflow = BufferOverflow.DROP_OLDEST
-    )
-
-    private val lifecycleObserver = object : LifecycleEventObserver {
-        override fun onStateChanged(source: LifecycleOwner, event: Lifecycle.Event) {
-            lifeCycleState.tryEmit(source.lifecycle.currentState)
-            if (source.lifecycle.currentState == Lifecycle.State.DESTROYED) {
-                source.lifecycle.removeObserver(this)
-            }
-        }
-    }
-
     private val locationUpdates: Flow<Location> = hasLocationPermission
         .filter { it }
         .flatMapLatest { locationObserver.observeLocationUpdates() }
@@ -50,18 +36,6 @@ class MainViewModel(application: Application) : AndroidViewModel(application) {
     fun onLocationPermissionGranted() {
         hasLocationPermission.value = true
     }
-
-    fun startObservingLifecycle(lifecycleOwner: LifecycleOwner) {
-        lifecycleOwner.lifecycle.addObserver(lifecycleObserver)
-    }
-
-    private fun <T> Flow<T>.whenAtLeast(requiredState: Lifecycle.State): Flow<T> {
-        return lifeCycleState.map { state -> state.isAtLeast(requiredState) }
-            .distinctUntilChanged()
-            .flatMapLatest {
-                if (it) this else emptyFlow()
-            }
-    }
 }
 
 data class ViewState(