android backstack adjustments

Author: Patrick Jackson

android/src/main/java/com/jackson/openlibrary/AndroidNavigator.kt

@@ -5,6 +5,9 @@ import android.app.Application
 import android.os.Bundle
 import androidx.appcompat.app.AppCompatActivity
 import androidx.fragment.app.Fragment
+import androidx.navigation.NavDirections
+import androidx.navigation.NavOptions
+import androidx.navigation.NavOptionsBuilder
 import androidx.navigation.findNavController
 import com.jackson.openlibrary.store.CompletedFragment
 import com.jackson.openlibrary.store.DetailsFragment
@@ -34,16 +37,17 @@ class AndroidNavigator : Navigator, Application.ActivityLifecycleCallbacks {
         } else {
             val navController = currentActivity!!.findNavController(R.id.nav_host_fragment)
 
+            val navOptions = NavOptions.Builder()
+                    .setPopUpTo(navController.currentDestination!!.id, true)
+                    .build()
 
-            navController.navigate(
-                    when (screen) {
-                        Screen.BOOK_DETAILS -> R.id.detailsFragment
-                        Screen.COMPLETED_LIST -> R.id.completedListFragment
-                        Screen.READING_LIST -> R.id.readingListFragment
-                        Screen.SEARCH -> R.id.searchFragment
-                        else -> throw IllegalArgumentException("Screen $screen is not handled in AndroidNavigator")
-                    }
-            )
+            when (screen) {
+                Screen.BOOK_DETAILS -> navController.navigate(R.id.detailsFragment)
+                Screen.COMPLETED_LIST -> navController.navigate(R.id.completedListFragment, null, navOptions)
+                Screen.READING_LIST -> navController.navigate(R.id.readingListFragment, null, navOptions)
+                Screen.SEARCH -> navController.navigate(R.id.searchFragment)
+                else -> throw IllegalArgumentException("Screen $screen is not handled in AndroidNavigator")
+            }
         }
     }
 

android/src/main/res/navigation/nav_graph.xml

@@ -4,11 +4,7 @@
     xmlns:tools="http://schemas.android.com/tools"
     app:startDestination="@id/readingListFragment">
 
-    <activity
-        android:id="@+id/mainActivity"
-        android:name="com.jackson.openlibrary.MainActivity"
-        android:label="fragment_search"
-        tools:layout="@layout/activity_main" />
+
     <fragment
         android:id="@+id/readingListFragment"
         android:name="com.jackson.openlibrary.store.ReadingListFragment"

common/src/commonMain/kotlin/com/willowtreeapps/common/AppState.kt

@@ -1,5 +1,6 @@
 package com.willowtreeapps.common
 
+import com.willowtreeapps.common.middleware.Screen
 import com.willowtreeapps.common.repo.Book
 import kotlin.reflect.KProperty0
 
@@ -12,6 +13,7 @@ data class AppState(val isLoadingItems: Boolean = false,
                     val completed: Set<Book> = setOf(),
                     val currentList: KProperty0<Set<Book>>? = null,
                     val errorMsg: String = "",
+                    val currentScreen: Screen = Screen.READING_LIST,
                     val settings: UserSettings = UserSettings.defaults()) {
     companion object {
         val INITIAL_STATE = AppState()

common/src/commonMain/kotlin/com/willowtreeapps/common/LibraryApp.kt

@@ -11,6 +11,7 @@ import com.willowtreeapps.common.ui.LibraryView
 import com.willowtreeapps.common.ui.PresenterFactory
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.launch
+import org.reduxkotlin.combineReducers
 import kotlin.coroutines.CoroutineContext
 
 class LibraryApp(navigator: Navigator,
@@ -25,7 +26,7 @@ class LibraryApp(navigator: Navigator,
     override val networkThunks = NetworkThunks(networkContext, bookRepository)
 
     val store by lazy {
-        createStore(reducer, AppState.INITIAL_STATE, applyMiddleware(createThunkMiddleware2(),
+        createStore(combineReducers(reducer, navigationReducer), AppState.INITIAL_STATE, applyMiddleware(createThunkMiddleware2(),
                 uiActionMiddleware(networkThunks),
                 databaseMiddleware.middleware,
                 navigationMiddleware::dispatch,
@@ -35,6 +36,7 @@ class LibraryApp(navigator: Navigator,
     init {
         CoroutineScope(uiContext).launch {
             //do any initialization here
+            dispatch(NavigationActions.GotoScreen(state.currentScreen))
         }
     }
 

common/src/commonMain/kotlin/com/willowtreeapps/common/NavigationReducer.kt

@@ -0,0 +1,10 @@
+package com.willowtreeapps.common
+
+
+val navigationReducer = castingReducer { state: AppState, action ->
+    if (action is NavigationActions.GotoScreen) {
+        state.copy(currentScreen = action.screen)
+    } else {
+        state
+    }
+}

common/src/commonMain/kotlin/com/willowtreeapps/common/Reducers.kt

@@ -29,13 +29,14 @@ val reducer = castingReducer { state: AppState, action ->
         is PrevBook -> state.copy(selectedBook = state.searchBooks[state.currentSearchIndex() - 1])
         is NextBook -> state.copy(selectedBook = state.searchBooks[state.currentSearchIndex() + 1])
 
-
         else -> {
 //            Logger.d("Action ${action::class.simpleName} not handled")
             state
         }
     }
 }
+
+
 inline fun <reified T> castingReducer(crossinline reducer: ((T, Any) -> Any)): Reducer = { state: Any, action: Any ->
     if (state is T) {
         reducer(state as T, action)