Show location updates when the app is active

app/build.gradle

@@ -38,6 +38,7 @@ dependencies {
     implementation 'androidx.appcompat:appcompat:1.3.1'
     implementation 'com.google.android.material:material:1.4.0'
     implementation "androidx.lifecycle:lifecycle-viewmodel-ktx:2.4.0"
+    implementation "androidx.lifecycle:lifecycle-runtime-ktx:2.4.0"
     implementation "androidx.fragment:fragment-ktx:1.3.6"
     implementation 'com.google.android.gms:play-services-location:18.0.0'
     implementation 'androidx.constraintlayout:constraintlayout:2.1.1'

app/src/main/java/com/hicham/flowlifecycle/MainFragment.kt

@@ -1,12 +1,51 @@
 package com.hicham.flowlifecycle
 
+import android.Manifest
+import android.content.pm.PackageManager.PERMISSION_GRANTED
 import android.os.Bundle
 import android.view.View
+import androidx.activity.result.contract.ActivityResultContracts
 import androidx.fragment.app.Fragment
+import androidx.fragment.app.viewModels
+import androidx.lifecycle.flowWithLifecycle
+import androidx.lifecycle.lifecycleScope
+import com.hicham.flowlifecycle.databinding.FragmentMainBinding
+import kotlinx.coroutines.flow.launchIn
+import kotlinx.coroutines.flow.onEach
+import kotlinx.coroutines.launch
 
-class MainFragment: Fragment(R.layout.fragment_main) {
+class MainFragment : Fragment(R.layout.fragment_main) {
+    private val viewModel: MainViewModel by viewModels()
+
+    val requestPermissionLauncher =
+        registerForActivityResult(
+            ActivityResultContracts.RequestPermission()
+        ) { isGranted: Boolean ->
+            if (isGranted) {
+                viewModel.onLocationPermissionGranted()
+            } else {
+                // TODO
+            }
+        }
 
     override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
         super.onViewCreated(view, savedInstanceState)
+        val binding = FragmentMainBinding.bind(view)
+
+        val hasLocationPermission =
+            requireContext().checkSelfPermission(Manifest.permission.ACCESS_FINE_LOCATION) == PERMISSION_GRANTED
+
+        if (hasLocationPermission) {
+            viewModel.onLocationPermissionGranted()
+        } else {
+            requestPermissionLauncher.launch(Manifest.permission.ACCESS_FINE_LOCATION)
+        }
+
+        viewLifecycleOwner.lifecycleScope.launch {
+            viewModel.locationUpdates
+                .flowWithLifecycle(viewLifecycleOwner.lifecycle)
+                .onEach { binding.location.text = "${it.latitude} ${it.longitude}" }
+                .launchIn(this)
+        }
     }
 }

app/src/main/java/com/hicham/flowlifecycle/MainViewModel.kt

@@ -0,0 +1,30 @@
+package com.hicham.flowlifecycle
+
+import android.annotation.SuppressLint
+import android.app.Application
+import android.location.Location
+import androidx.lifecycle.AndroidViewModel
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.filter
+import kotlinx.coroutines.flow.flatMapLatest
+
+class MainViewModel(application: Application) : AndroidViewModel(application) {
+    private val locationObserver = LocationObserver(application)
+
+    private val hasLocationPermission = MutableStateFlow(false)
+
+    @SuppressLint("MissingPermission")
+    val locationUpdates: Flow<Location> = hasLocationPermission
+        .filter { it }
+        .flatMapLatest { locationObserver.observeLocationUpdates() }
+
+    fun onLocationPermissionGranted() {
+        hasLocationPermission.value = true
+    }
+}
+
+data class ViewState(
+    val location: Location,
+    val nearbyLocations: List<String>
+)

app/src/main/res/layout/activity_main.xml

@@ -7,13 +7,13 @@
     tools:context=".MainActivity">
 
     <androidx.fragment.app.FragmentContainerView
+        android:id="@+id/fragment_container"
+        android:name="com.hicham.flowlifecycle.MainFragment"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
-        android:text="Hello World!"
         app:layout_constraintBottom_toBottomOf="parent"
         app:layout_constraintLeft_toLeftOf="parent"
         app:layout_constraintRight_toRightOf="parent"
-        app:layout_constraintTop_toTopOf="parent"
-        android:name="com.hicham.flowlifecycle.MainFragment"/>
+        app:layout_constraintTop_toTopOf="parent" />
 
 </androidx.constraintlayout.widget.ConstraintLayout>

app/src/main/res/layout/fragment_main.xml

@@ -1,6 +1,16 @@
 <?xml version="1.0" encoding="utf-8"?>
 <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
     android:layout_width="match_parent"
     android:layout_height="match_parent">
 
+    <androidx.appcompat.widget.AppCompatTextView
+        android:id="@+id/location"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        app:layout_constraintBottom_toBottomOf="parent"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent" />
+
 </androidx.constraintlayout.widget.ConstraintLayout>