How to update Room database entry through UI?

Question

I have an application that allows the user to add Goats with their details such as name, breed, age and gender and additional info. I just created a function in the GoatDao to update the goatInfo parameter and it works inside the Database inspection thing.

 @Query("UPDATE goat SET goatInfo=:newInfo WHERE id=:id")
    fun updateInfoByQuery(id: Int, newInfo: String)

And this is my Goat entity ˇ

@Entity
data class Goat(
    val goatName: String,
    val goatAge: String,
    val goatBreed: String,
    val goatInfo: String,
    val goatGender: String,
    @PrimaryKey(autoGenerate = true)
    val id: Int = 0
)

I'm stuck on how I could implement the updateInfoByQuery function into UI. I want to have a dialog that launches when a goat is clicked and allows me to update it.

How do I implement that function in the UI?

@Composable
fun UpdateDialog(state: GoatState, onDismiss: () -> Unit) {

    val patrick = FontFamily(
        Font(R.font.patrick_hand_sc, FontWeight.Black, FontStyle.Normal)
    )


    Dialog(
        onDismissRequest = { onDismiss() },
        properties = DialogProperties(usePlatformDefaultWidth = false)
    ) {
        

 }
}

This is my main goat screen code:

@OptIn(ExperimentalMaterial3Api::class)
@Composable
fun GoatScreen( state: GoatState, onEvent: (GoatEvent) -> Unit) {
    val patrick = FontFamily(
        Font(R.font.patrick_hand_sc, FontWeight.Black, FontStyle.Normal)
    )



 


    Scaffold(
        containerColor = colorResource(R.color.brunswick_green),
        topBar = {
            CenterAlignedTopAppBar(
                modifier = Modifier
                    //.padding(6.dp)
                    .shadow(
                        elevation = 5.dp,
                        spotColor = Color.DarkGray,
                        shape = RoundedCornerShape(10.dp)
                    ),
                colors = topAppBarColors(
                    containerColor = colorResource(R.color.brunswick_green),
                            titleContentColor = MaterialTheme . colorScheme . primary,
                ),
                title = {

                    Text(
                        "Goats",
                        fontFamily = patrick,
                        color = colorResource(R.color.timberwolf),
                        textAlign = TextAlign.Center,
                        fontSize = 50.sp
                    )


                },

                )
        },
        floatingActionButton = {
            FloatingActionButton(onClick = { onEvent(GoatEvent.ShowDialog) }) {
                Icon(Icons.Default.Add, contentDescription = "Add")
            }
        },

    ) {
        padding ->
        if(state.isAddingGoat) {
            AddGoatDialog(state = state, onEvent = onEvent, modifier = Modifier )
        }



        LazyColumn(contentPadding = padding,
            modifier = Modifier.fillMaxSize(),
            verticalArrangement = Arrangement.spacedBy(16.dp) ) {
            item {
                Row(modifier = Modifier
                    .padding(8.dp)
                    .shadow(
                        elevation = 5.dp,
                        spotColor = Color.DarkGray,
                        shape = RoundedCornerShape(10.dp)
                    )
                    .background(color = colorResource(R.color.brunswick_green))
                    .horizontalScroll(rememberScrollState()),
                    verticalAlignment = Alignment.CenterVertically
                    ) {
                    SortType.entries.forEach { sortType ->
                        Row(modifier = Modifier.clickable { onEvent(GoatEvent.SortGoats(sortType)) }) {
                            RadioButton(selected = state.sortType == sortType, onClick = { onEvent(GoatEvent.SortGoats(sortType)) }, colors = RadioButtonDefaults.colors(Color.LightGray))
                            Text(text = sortType.name, color = colorResource(R.color.timberwolf))
                        }
                        
                    }

                }

                }


            items(state.goats) {goat ->
                Row(modifier = Modifier
                    .padding(12.dp)
                    .clickable {

                    }
                    .fillMaxWidth()
                    .background(color = Color.LightGray, shape = RoundedCornerShape(16.dp))
                    .padding(40.dp)) {



                    Column {
                        Text(text = "${goat.goatName} ${goat.goatAge}", fontFamily = patrick, fontSize = 20.sp
                        )
                    
                        Text(text = "${goat.goatBreed} ${goat.goatInfo}", fontFamily = patrick, fontSize = 20.sp)
                    }


                    
                    IconButton(onClick = { 
                        onEvent(GoatEvent.DeleteGoat(goat)) }) {
                        Icon(imageVector = Icons.Default.Delete, contentDescription = "Delete Goat")
                    }
                }
            }


        }

    }
}

EDIT: My ViewModel

package com.example.goatdatabase

import androidx.lifecycle.ViewModel
import androidx.lifecycle.viewModelScope
import kotlinx.coroutines.ExperimentalCoroutinesApi
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 GoatViewModel(private val dao: GoatDao): ViewModel() {
    private val _state = MutableStateFlow(GoatState())
    private val _sortType = MutableStateFlow(SortType.NAME)
    @OptIn(ExperimentalCoroutinesApi::class)
    private val _goats = _sortType
        .flatMapLatest { sortType ->
            when(sortType) {
                SortType.NAME -> dao.getGoatsOrderedByName()
                SortType.BREED -> dao.getGoatsOrderedByBreed()
                SortType.AGE -> dao.getGoatsOrderedByAge()
                SortType.GENDER -> dao.getGoatsOrderedByGender()
            }
        }
        .stateIn(viewModelScope, SharingStarted.WhileSubscribed(), emptyList())
    val state = combine(_state, _sortType, _goats) { state, sortType, goats ->
                state.copy(goats = goats, sortType = sortType) }
        .stateIn(viewModelScope, SharingStarted.WhileSubscribed(5000), GoatState())



    fun onEvent(event: GoatEvent) {
        when(event) {
            is GoatEvent.DeleteGoat -> {
                viewModelScope.launch { dao.deleteGoat(event.goat) }
            }
            GoatEvent.HideDialog -> {
                _state.update { it.copy(isAddingGoat = false) }
            }
            GoatEvent.SaveGoat -> {
                val goatName = state.value.goatName
                val goatAge = state.value.goatAge
                val goatBreed = state.value.goatBreed
                val goatInfo = state.value.goatInfo
                val goatGender = state.value.goatGender

                if (goatName.isBlank() || goatAge.isBlank() || goatBreed.isBlank() || goatInfo.isBlank()) {
                    return
                }

                val goat = Goat(goatName = goatName, goatAge = goatAge, goatBreed = goatBreed, goatInfo = goatInfo, goatGender = goatGender)
                viewModelScope.launch { dao.insertGoat(goat) }
                _state.update{it.copy(isAddingGoat = false,
                    goatName = "",
                    goatInfo = "",
                    goatBreed = "",
                    goatAge = ""
                    )}

            }
            is GoatEvent.SetGoatAge -> {
                _state.update {it.copy(goatAge = event.goatAge)}
            }
            is GoatEvent.SetGoatBreed -> {
                _state.update{it.copy(goatBreed = event.goatBreed)}
            }
            is GoatEvent.SetGoatInfo -> {
                _state.update { it.copy(goatInfo = event.goatInfo) }
            }
            is GoatEvent.SetGoatName -> {
                _state.update { it.copy(goatName = event.goatName) }
            }
            GoatEvent.ShowDialog -> {
                _state.update{it.copy(isAddingGoat = true)}
            }

            is GoatEvent.SortGoats -> {
                _sortType.value = event.sortType
            }

            is GoatEvent.SetGoatGender -> {
                _state.update {it.copy(goatGender = event.goatGender)}
            }

           
        }
    }
}

EDIT ::::

I updated the view model to launch a dialog for each goat but when I enter data and click save, nothing changes??

@Composable
fun UpdateDialog(onEvent: (GoatEvent) -> Unit, state: GoatState, onDismiss: () -> Unit) {

val patrick = FontFamily(
    Font(R.font.patrick_hand_sc, FontWeight.Black, FontStyle.Normal)
)
 //   val goat = Goat(state.goatName, state.goatAge, state.goatBreed, state.goatGender, state.goatInfo)


   Dialog(
      onDismissRequest = { onEvent(GoatEvent.HideNewDialog) },
        properties = DialogProperties(usePlatformDefaultWidth = false)

    ) {
        Column {


       TextField( value = state.goatInfo, onValueChange = {onEvent(GoatEvent.SetGoatInfo(it))},
           placeholder = { Text(text = "Goat Info") })

       Button(onClick = { onEvent(GoatEvent.SaveGoat) }) {
           Text(text = "Save")

       }

        }
 }
}

This down here is in the view model:

 GoatEvent.ShowNewDialog -> {
                _state.update{it.copy(isUpdatingGoat = true)}
            }

is GoatEvent.UpdateGoatInfo -> {
                dao.updateInfoByQuery(id = state.value.goatId, newInfo = state.value.goatInfo)
            }

Answer 1

From the comments, you have two different approaches

• Directly update a specific field (goatInfo) of a Goat entity in the database using a custom @Query method (updateInfoByQuery). That would require specific methods for each field you might want to update, which can lead to boilerplate code if you have many fields or complex entities.

• Replace the entire Goat entity using the @Insert method with OnConflictStrategy.REPLACE, as suggested by Leviathan. That does simplify the code by allowing the entire entity to be updated at once if the primary key matches an existing entity in the database.

Make sure your Goat entity is set up to be replaced entirely when an existing primary key is detected. That is achieved by specifying a conflict strategy in the @Insert annotation in your DAO:

@Dao
interface GoatDao {
    @Insert(onConflict = OnConflictStrategy.REPLACE)
    fun saveGoat(goat: Goat)
    
    // Other DAO methods
}

That saveGoat method will insert a new Goat into the database if the id does not exist; if the id does exist, it will replace the existing Goat with the new one you provide.

To integrate this approach with your UI, especially within the UpdateDialog, you would need to make sure your dialog collects not just the goatInfo, but potentially any other fields you want to allow the user to update. That might require additional TextField components for each field, or just the ones you expect to change frequently.

Modify your ViewModel to handle a new event that captures the intent to save or update a goat entity. That involves either creating a new event or repurposing an existing one to carry a complete Goat object.

fun onEvent(event: GoatEvent) {
    when(event) {
        is GoatEvent.SaveOrUpdateGoat -> saveOrUpdateGoat(event.goat)
        // Handle other events
    }
}

private fun saveOrUpdateGoat(goat: Goat) {
    viewModelScope.launch {
        dao.saveGoat(goat)
        // After saving, you may want to refresh your goat list or perform other UI updates
    }
}

When the user completes their updates in the UpdateDialog and clicks the save button, collect the updated goat information into a Goat object (including the id to make sure the database knows this is an update) and trigger the SaveOrUpdateGoat event with this object.

---

I just cannot get my UpdateDialog to read the goat Info value (or any other) from the goat that I clicked on.

TextField( value = state.goatInfo, onValueChange = 
 {onEvent(GoatEvent.SetGoatInfo(it))},
 placeholder = { Text(goat.goatInfo) })

The UpdateDialog is there to allow editing of a goat's details, but the current implementation struggles with displaying the selected goat's goatInfo (or other attributes) within the TextField.

Modify the state handling in your ViewModel to include a property for the currently selected goat. When a goat is selected for editing, this property should be updated to reflect the selected goat. That selected goat's information can then be used to populate the TextField values in the UpdateDialog.

The UpdateDialog should be modified to accept a Goat object directly. That way, it can use the properties of this goat object to initialize the TextField values.

@Composable
fun UpdateDialog(goat: Goat, onDismiss: () -> Unit, onUpdate: (Goat) -> Unit) {
    var updatedGoatInfo by remember { mutableStateOf(goat.goatInfo) }

    Dialog(onDismissRequest = { onDismiss() }) {
        Column {
            TextField(
                value = updatedGoatInfo,
                onValueChange = { updatedGoatInfo = it },
                label = { Text("Goat Info") },
                placeholder = { Text(goat.goatInfo) }
            )
            // Other TextFields for goatName, goatBreed, etc., as needed
            Button(onClick = { 
                // Create a new Goat object with the updated info to pass back
                val updatedGoat = goat.copy(goatInfo = updatedGoatInfo)
                onUpdate(updatedGoat)
                onDismiss()
            }) {
                Text("Save")
            }
        }
    }
}

The onUpdate lambda should trigger an event or function in your ViewModel that updates the goat's information in the database. That part of the solution focuses on using the copy function of the data class to create a new Goat instance with the updated information, which is then passed back to be saved.

Make sure your ViewModel and the event handling mechanism are set up to handle this updated Goat object. The event or function triggered by onUpdate should result in a database update, either by calling the saveGoat method directly (if using @Insert(onConflict = OnConflictStrategy.REPLACE)) or by another appropriate mechanism.

---

How do I tell the view model that it's the specified goat object we're talking about?

Modify the state handling in your ViewModel to include a property for the currently selected goat. When a goat is selected for editing, this property should be updated to reflect the selected goat.
That selected goat's information can then be used to populate the TextField values in the UpdateDialog.

First, you would need a way to keep track of which goat has been selected for editing. That involves adding a property in your ViewModel that can hold the currently selected goat. That property can be part of your existing state or a separate MutableStateFlow or LiveData:

class GoatViewModel(private val dao: GoatDao) : ViewModel() {
    // Assuming GoatState is your UI state class
    private val _selectedGoat = MutableStateFlow<Goat?>(null)
    val selectedGoat: StateFlow<Goat?> = _selectedGoat.asStateFlow()

    // Your existing code
}

When a goat is selected (clicked on) in the UI, you should update this _selectedGoat property. You can do this by defining an event or function in your ViewModel that sets the selected goat:

fun selectGoat(goat: Goat) {
    _selectedGoat.value = goat
}

Now that your ViewModel knows which goat is selected, you can use this information to populate the UpdateDialog fields. You will show the UpdateDialog when _selectedGoat is not null and pass the selected goat to it:

@Composable
fun YourComposable(viewModel: GoatViewModel) {
    // Observing the selectedGoat state
    val selectedGoat by viewModel.selectedGoat.collectAsState()

    // When a goat is selected, show the UpdateDialog
    selectedGoat?.let { goat ->
        UpdateDialog(
            goat = goat,
            onDismiss = { viewModel.selectGoat(null) }, // Clear the selection on dismiss
            onUpdate = { updatedGoat -> 
                viewModel.updateGoat(updatedGoat) // Implement this in ViewModel
            }
        )
    }
}

When the "Save" button is clicked in the UpdateDialog, the onUpdate lambda should trigger a function in your ViewModel that updates the goat's information in the database:

fun updateGoat(updatedGoat: Goat) {
    viewModelScope.launch {
        dao.saveGoat(updatedGoat) // Assuming you are using the @Insert(onConflict = REPLACE) strategy
        _selectedGoat.value = null // Optionally clear the selected goat after update
    }
}

Your workflow would be:

User Interface (UI)                     ViewModel                          Database
     |                                      |                                  |
     | --- Select Goat for Editing ------>  |                                  |
     |                                      |                                  |
     |                                      | --- Update _selectedGoat ----->  |
     |                                      |        (MutableStateFlow)        |
     |                                      |                                  |
     | <--- Observe _selectedGoat -------   |                                  |
     |      (Collect as State)              |                                  |
     |                                      |                                  |
     |                                      |                                  |
     | --- Show UpdateDialog with ------->  |                                  |
     |     Selected Goat's Info             |                                  |
     |                                      |                                  |
     |                                      |                                  |
     | --- User Updates Goat Info ------->  |                                  |
     |     and Clicks Save                  |                                  |
     |                                      |                                  |
     |                                      | --- Update Goat in Database -->  |
     |                                      |     (saveGoat/Update Query)      |
     |                                      |                                  |
     |                                      | <--- Optionally Clear ---------  |
     |                                      |     _selectedGoat                |
     |                                      |                                  |

1. A goat is selected for editing, updating the ViewModel's selectedGoat.
2. The UpdateDialog displays, pre-filled with the selected goat's information.
3. Changes made in the dialog are saved back to the database through the ViewModel.

That does illustrate a basic state management and ViewModel patterns but also demonstrates how to manipulate and display dynamic data based on user interaction in a Jetpack Compose application.