Remember the last program that was running (#123)

Author: jblebrun

app/build.gradle.kts

@@ -73,6 +73,7 @@ dependencies {
     implementation(libs.androidx.room.ktx)
     ksp(libs.androidx.room.compiler)
 
+    implementation(libs.androidx.datastore.preferences)
 
     implementation(libs.androidx.core.ktx)
     implementation(libs.androidx.lifecycle.runtime.ktx)

app/src/main/java/com/emerjbl/ultra8/Ultra8Application.kt

@@ -1,6 +1,10 @@
 package com.emerjbl.ultra8
 
 import android.app.Application
+import android.content.Context
+import androidx.datastore.core.DataStore
+import androidx.datastore.preferences.core.Preferences
+import androidx.datastore.preferences.preferencesDataStore
 import androidx.room.RoomDatabase
 import com.emerjbl.ultra8.data.Chip8StateStore
 import com.emerjbl.ultra8.data.ProgramStore
@@ -10,8 +14,11 @@ interface Provider {
     val chip8StateStore: Chip8StateStore
     val programStore: ProgramStore
     val db: RoomDatabase
+
 }
 
+val Context.preferences: DataStore<Preferences> by preferencesDataStore(name = "settings")
+
 class Ultra8Application : Application() {
     val provider = object : Provider {
         override val chip8StateStore by lazy { Chip8StateStore(db.chip8StateDao()) }

app/src/main/java/com/emerjbl/ultra8/data/ProgramStore.kt

@@ -3,14 +3,18 @@ package com.emerjbl.ultra8.data
 import android.content.Context
 import android.net.Uri
 import android.provider.MediaStore.MediaColumns
+import androidx.datastore.preferences.core.edit
+import androidx.datastore.preferences.core.stringPreferencesKey
 import androidx.room.Dao
 import androidx.room.Delete
 import androidx.room.Entity
 import androidx.room.PrimaryKey
 import androidx.room.Query
 import androidx.room.Upsert
+import com.emerjbl.ultra8.preferences
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.withContext
 
 /** A single program entry. */
@@ -55,6 +59,17 @@ class ProgramStore(
 ) {
     fun programsFlow(): Flow<List<Program>> = programDao.allFlow()
 
+    val selectedProgram = context.preferences.data.map {
+        (it[SELECTED_PROGRAM_KEY] ?: DEFAULT_PROGRAM_NAME)
+    }
+
+    suspend fun setSelectedProgram(name: String) {
+        context.preferences.edit {
+            it[SELECTED_PROGRAM_KEY] = name
+        }
+    }
+
+
     suspend fun addForUri(uri: Uri): Program =
         withContext(Dispatchers.IO) {
             val name = withContext(Dispatchers.IO) {
@@ -87,4 +102,9 @@ class ProgramStore(
         programDao.updateCyclesPerTick(name, cyclesPerTick)
 
     suspend fun remove(name: String) = programDao.remove(Program(name, false, 0))
+
+    companion object {
+        private val SELECTED_PROGRAM_KEY = stringPreferencesKey("lastProgram")
+        private const val DEFAULT_PROGRAM_NAME = "breakout"
+    }
 }

app/src/main/java/com/emerjbl/ultra8/ui/screen/AppEntryPoint.kt

@@ -28,6 +28,10 @@ fun AppEntryPoint() {
     val programs = topLevelViewModel.programs.collectAsState(emptyList())
     val selectedProgram = topLevelViewModel.selectedProgram.collectAsState("")
 
+    if (selectedProgram.value == "") {
+        // TODO - Maybe show some splash screen kind of thing
+        return
+    }
     val drawerState = rememberDrawerState(initialValue = DrawerValue.Closed)
 
     val windowFocused = LocalWindowInfo.current.isWindowFocused
@@ -55,8 +59,8 @@ fun AppEntryPoint() {
                         scope.launch {
                             drawerState.close()
                         }
-                        if (topLevelViewModel.selectedProgram.value != program.name) {
-                            topLevelViewModel.selectedProgram.value = program.name
+                        if (selectedProgram.value != program.name) {
+                            topLevelViewModel.setSelectedProgram(program.name)
                             navController.navigate(PlayGame(program.name))
                         }
                     },

app/src/main/java/com/emerjbl/ultra8/ui/screen/Ultra8NavHost.kt

@@ -17,7 +17,7 @@ fun Ultra8NavHost(
     resetEvents: Flow<Unit>,
     onDrawerOpen: () -> Unit,
 ) {
-    NavHost(navController, startDestination = PlayGame("breakout")) {
+    NavHost(navController, startDestination = PlayGame(selectedProgram)) {
         composable<PlayGame> { entry ->
             val routeProgram = entry.toRoute<PlayGame>().programName
             // During navigation, the previous route is still in composition for a few

app/src/main/java/com/emerjbl/ultra8/ui/viewmodel/TopLevelViewModel.kt

@@ -10,20 +10,26 @@ import com.emerjbl.ultra8.data.Program
 import com.emerjbl.ultra8.data.ProgramStore
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.MutableSharedFlow
-import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.launch
 
 class TopLevelViewModel(
     private val programStore: ProgramStore,
 ) : ViewModel() {
+
     val programs: Flow<List<Program>> = programStore.programsFlow()
 
     // Pass reset events from the navigation drawer down to gameplay children.
     // This is one case where I feel like it's OK to break unidirectional dataflow.
     // But I'll probably find a better approach eventually.
     val resetEvents = MutableSharedFlow<Unit>(extraBufferCapacity = 1)
 
-    val selectedProgram = MutableStateFlow("")
+    val selectedProgram = programStore.selectedProgram
+
+    fun setSelectedProgram(name: String) {
+        viewModelScope.launch {
+            programStore.setSelectedProgram(name)
+        }
+    }
 
     fun removeProgram(name: String) {
         viewModelScope.launch {

gradle/libs.versions.toml

@@ -1,5 +1,6 @@
 [versions]
 agp = "8.7.1"
+datastorePreferences = "1.1.1"
 kotlin = "2.0.21"
 coreKtx = "1.13.1"
 junit = "4.13.2"
@@ -29,6 +30,7 @@ ksp = "2.0.21-1.0.25"
 
 [libraries]
 androidx-core-ktx = { group = "androidx.core", name = "core-ktx", version.ref = "coreKtx" }
+androidx-datastore-preferences = { module = "androidx.datastore:datastore-preferences", version.ref = "datastorePreferences" }
 androidx-lifecycle-viewmodel-compose = { module = "androidx.lifecycle:lifecycle-viewmodel-compose", version.ref = "lifecycleViewmodelCompose" }
 androidx-room-compiler = { module = "androidx.room:room-compiler", version.ref = "roomRuntime" }
 androidx-room-runtime = { module = "androidx.room:room-runtime", version.ref = "roomRuntime" }