Add view model and modify MainActivity. Should be everything needed to start testing near-basic functionality and begin tweaking as needed!

app/src/main/java/com/hyperling/expensetracker/ExpenseViewModel.kt

@@ -0,0 +1,98 @@
+package com.hyperling.expensetracker
+
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.viewModelScope
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.SharingStarted
+import kotlinx.coroutines.flow.combine
+import kotlinx.coroutines.flow.flatMapLatest
+import kotlinx.coroutines.flow.stateIn
+import kotlinx.coroutines.flow.update
+import kotlinx.coroutines.launch
+
+class ExpenseViewModel (
+    private val dao: ExpenseDao,
+): ViewModel() {
+
+    private val _sortType = MutableStateFlow(SortType.NAME)
+    private val _state = MutableStateFlow(ExpenseState())
+
+    private val _expenses = _sortType
+        .flatMapLatest { sortType ->
+            when(sortType) {
+                SortType.NAME -> dao.selectExpensesName()
+                SortType.COST -> dao.selectExpensesCost()
+                SortType.RATE -> dao.selectExpensesRate()
+            }
+        }.stateIn(viewModelScope, SharingStarted.WhileSubscribed(), emptyList())
+
+    val state = combine(_state, _sortType, _expenses) { state, sortType, expenses ->
+        state.copy(
+            expenses = expenses,
+            sortType = sortType
+        )
+    }.stateIn(viewModelScope, SharingStarted.WhileSubscribed(5000), ExpenseState())
+
+    fun onEvent(event: ExpenseEvent) {
+        when(event) {
+            is ExpenseEvent.DeleteExpense -> {
+                viewModelScope.launch {
+                    dao.deleteExpense(event.expense)
+                }
+            }
+            ExpenseEvent.HideDialog -> {
+                _state.update { it.copy(
+                    isAddingExpense = false
+                ) }
+            }
+            ExpenseEvent.SaveExpense -> {
+                val name = state.value.name
+                val cost = state.value.cost
+                val rate = state.value.rate
+
+                if (name.isBlank()
+                    || cost.isBlank()
+                    //|| rate.isBlank() # TBD, enable this once Rate is working.
+                ) {
+                    return
+                }
+
+                val expense = Expense(name, cost, rate)
+
+                viewModelScope.launch {
+                    dao.upsertExpense(expense)
+                }
+
+                _state.update { it.copy(
+                    isAddingExpense = false,
+                    name = "",
+                    cost = "",
+                    rate = Rate.MONTHLY,
+                ) }
+            }
+            is ExpenseEvent.SetName -> {
+                _state.update { it.copy(
+                    name = event.name
+                ) }
+            }
+            is ExpenseEvent.SetCost -> {
+                _state.update { it.copy(
+                    cost = event.cost
+                ) }
+            }
+            is ExpenseEvent.SetRate -> {
+                _state.update { it.copy(
+                    rate = event.rate
+                ) }
+            }
+            ExpenseEvent.ShowDialog -> {
+                _state.update { it.copy(
+                    isAddingExpense = true
+                ) }
+            }
+            is ExpenseEvent.SortExpenses -> {
+                _sortType.value = event.sortType
+            }
+        }
+    }
+}

app/src/main/java/com/hyperling/expensetracker/MainActivity-OLD.kt

@@ -0,0 +1,140 @@
+package com.hyperling.expensetracker
+
+import android.content.Context
+import android.content.Intent
+import android.os.Bundle
+import androidx.activity.ComponentActivity
+import androidx.activity.compose.setContent
+import androidx.activity.enableEdgeToEdge
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.padding
+import androidx.compose.material3.Button
+import androidx.compose.material3.FloatingActionButton
+import androidx.compose.material3.Scaffold
+import androidx.compose.material3.Surface
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.setValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.platform.LocalContext
+import androidx.compose.ui.tooling.preview.Preview
+import androidx.core.content.ContextCompat
+import androidx.core.content.ContextCompat.startActivity
+import com.hyperling.expensetracker.ui.theme.ExpenseTrackerTheme
+
+class MainActivityOLD : ComponentActivity() {
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        enableEdgeToEdge()
+        setContent {
+            ExpenseTrackerTheme {
+                Surface {
+                    Main()
+                }
+            }
+        }
+    }
+}
+
+// This seems like a great tutorial for what I need to do!
+// https://www.answertopia.com/jetpack-compose/a-jetpack-compose-room-database-and-repository-tutorial/
+
+@Composable
+fun Main() {
+    val context = LocalContext.current
+
+    var sumDaily by remember { mutableStateOf(0.0) }
+    var sumWeekly by remember { mutableStateOf(0.0) }
+    var sumMonthly by remember { mutableStateOf(0.0) }
+    var sumYearly by remember { mutableStateOf(0.0) }
+
+    val sums = mapOf(
+        "Daily" to sumDaily,
+        "Weekly" to sumWeekly,
+        "Monthly" to sumMonthly,
+        "Yearly" to sumYearly,
+    )
+
+    Column (
+        horizontalAlignment = Alignment.CenterHorizontally,
+        verticalArrangement = Arrangement.Center,
+        modifier = Modifier.fillMaxSize()
+    ) {
+
+        Text(
+            text = "Current Expense Summary"
+        )
+
+        //for ((name, value) in sums) {
+        sums.forEach { (name, value) ->
+            Row (
+                horizontalArrangement = Arrangement.End,
+            ){
+                Text(text = name + ": ")
+                Text(text = value.toString())
+            }
+        }
+
+        // FORTESTING
+        Text (text = String.format("%.2f",sumDaily))
+        Text (text = String.format("%.2f",sumWeekly))
+        Text (text = String.format("%.2f",sumMonthly))
+        Text (text = String.format("%.2f",sumYearly))
+
+        Row (
+            verticalAlignment = Alignment.CenterVertically,
+            horizontalArrangement = Arrangement.Center,
+        ) {
+            Button(onClick = {
+                val intent = Intent(context, NewExpenseActivity::class.java)
+                context.startActivity(intent)
+            }) {
+                Text(text = "Create New Expense")
+            }
+        }
+
+        Text(text = "Expenses")
+        // https://medium.com/@rowaido.game/implementing-the-room-library-with-jetpack-compose-590d13101fa7
+        /* TODO:
+            ForEach over all DB records, show it, and add its value to the summary.
+         */
+        val expenseArray = listOf(
+            Expense("Test", 180.0, 'Y', "My notes."),
+            Expense("Test2", 20.0, 'M', "My notes, 2!"),
+        )
+        expenseArray.forEach { expense ->
+            when (expense.freq) {
+                'D' -> sumYearly += (expense.cost * 365.25)
+                'W' -> sumYearly += (expense.cost * (365.25 / 7))
+                'M' -> sumYearly += (expense.cost * 12)
+                'Y' -> sumYearly += (expense.cost)
+            }
+
+            sumDaily = sumYearly / 365.25
+            sumWeekly = sumYearly / (365.25 / 7)
+            sumMonthly = sumYearly / 12
+        }
+
+        // FORTESTING
+        Text (text = String.format("$ %.2f",sumDaily))
+        Text (text = String.format("$ %.2f",sumWeekly))
+        Text (text = String.format("$ %.2f",sumMonthly))
+        Text (text = String.format("$ %.2f",sumYearly))
+    }
+}
+
+@Preview(showBackground = true)
+@Composable
+fun MainPreview() {
+    ExpenseTrackerTheme {
+        Main()
+    }
+}

app/src/main/java/com/hyperling/expensetracker/MainActivity.kt

@@ -1,140 +1,66 @@
 package com.hyperling.expensetracker
 
-import android.content.Context
+import com.hyperling.expensetracker.ui.theme.ExpenseTrackerTheme
-import android.content.Intent
 import android.os.Bundle
 import androidx.activity.ComponentActivity
 import androidx.activity.compose.setContent
 import androidx.activity.enableEdgeToEdge
-import androidx.compose.foundation.layout.Arrangement
+import androidx.activity.viewModels
-import androidx.compose.foundation.layout.Column
-import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.fillMaxSize
-import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.padding
-import androidx.compose.material3.Button
-import androidx.compose.material3.FloatingActionButton
 import androidx.compose.material3.Scaffold
 import androidx.compose.material3.Surface
 import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.collectAsState
 import androidx.compose.runtime.getValue
-import androidx.compose.runtime.mutableStateOf
-import androidx.compose.runtime.remember
-import androidx.compose.runtime.setValue
-import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
-import androidx.compose.ui.platform.LocalContext
 import androidx.compose.ui.tooling.preview.Preview
-import androidx.core.content.ContextCompat
+import androidx.lifecycle.ViewModel
-import androidx.core.content.ContextCompat.startActivity
+import androidx.lifecycle.ViewModelProvider
-import com.hyperling.expensetracker.ui.theme.ExpenseTrackerTheme
+import androidx.room.Room
+import androidx.compose.material3.Surface
 
 class MainActivity : ComponentActivity() {
+
+    private val _db by lazy {
+        Room.databaseBuilder(
+            applicationContext,
+            ExpenseDatabase::class.java,
+            "expenses.db"
+        ).build()
+    }
+    private val _viewModel by viewModels<ExpenseViewModel> (
+        factoryProducer = {
+            object : ViewModelProvider.Factory {
+                override fun <T : ViewModel> create(modelClass: Class<T>): T {
+                    return ExpenseViewModel(_db.dao) as T
+                }
+            }
+        }
+    )
+
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         enableEdgeToEdge()
         setContent {
             ExpenseTrackerTheme {
-                Surface {
+                val state by _viewModel.state.collectAsState()
-                    Main()
+                ExpenseScreen(
-                }
+                    state = state,
+                    onEvent = _viewModel::onEvent
+                )
             }
         }
     }
 }
 
-// This seems like a great tutorial for what I need to do!
+/*
-// https://www.answertopia.com/jetpack-compose/a-jetpack-compose-room-database-and-repository-tutorial/
-
-@Composable
-fun Main() {
-    val context = LocalContext.current
-
-    var sumDaily by remember { mutableStateOf(0.0) }
-    var sumWeekly by remember { mutableStateOf(0.0) }
-    var sumMonthly by remember { mutableStateOf(0.0) }
-    var sumYearly by remember { mutableStateOf(0.0) }
-
-    val sums = mapOf(
-        "Daily" to sumDaily,
-        "Weekly" to sumWeekly,
-        "Monthly" to sumMonthly,
-        "Yearly" to sumYearly,
-    )
-
-    Column (
-        horizontalAlignment = Alignment.CenterHorizontally,
-        verticalArrangement = Arrangement.Center,
-        modifier = Modifier.fillMaxSize()
-    ) {
-
-        Text(
-            text = "Current Expense Summary"
-        )
-
-        //for ((name, value) in sums) {
-        sums.forEach { (name, value) ->
-            Row (
-                horizontalArrangement = Arrangement.End,
-            ){
-                Text(text = name + ": ")
-                Text(text = value.toString())
-            }
-        }
-
-        // FORTESTING
-        Text (text = String.format("%.2f",sumDaily))
-        Text (text = String.format("%.2f",sumWeekly))
-        Text (text = String.format("%.2f",sumMonthly))
-        Text (text = String.format("%.2f",sumYearly))
-
-        Row (
-            verticalAlignment = Alignment.CenterVertically,
-            horizontalArrangement = Arrangement.Center,
-        ) {
-            Button(onClick = {
-                val intent = Intent(context, NewExpenseActivity::class.java)
-                context.startActivity(intent)
-            }) {
-                Text(text = "Create New Expense")
-            }
-        }
-
-        Text(text = "Expenses")
-        // https://medium.com/@rowaido.game/implementing-the-room-library-with-jetpack-compose-590d13101fa7
-        /* TODO:
-            ForEach over all DB records, show it, and add its value to the summary.
-         */
-        val expenseArray = listOf(
-            Expense("Test", 180.0, 'Y', "My notes."),
-            Expense("Test2", 20.0, 'M', "My notes, 2!"),
-        )
-        expenseArray.forEach { expense ->
-            when (expense.freq) {
-                'D' -> sumYearly += (expense.cost * 365.25)
-                'W' -> sumYearly += (expense.cost * (365.25 / 7))
-                'M' -> sumYearly += (expense.cost * 12)
-                'Y' -> sumYearly += (expense.cost)
-            }
-
-            sumDaily = sumYearly / 365.25
-            sumWeekly = sumYearly / (365.25 / 7)
-            sumMonthly = sumYearly / 12
-        }
-
-        // FORTESTING
-        Text (text = String.format("$ %.2f",sumDaily))
-        Text (text = String.format("$ %.2f",sumWeekly))
-        Text (text = String.format("$ %.2f",sumMonthly))
-        Text (text = String.format("$ %.2f",sumYearly))
-    }
-}
-
 @Preview(showBackground = true)
 @Composable
 fun MainPreview() {
     ExpenseTrackerTheme {
         Main()
     }
-}
+}
+*/