I have a Text function and want the value to chang...

# compose

[Guy Bieber]

I have a Text function and want the value to change when I change the state. There is no onChange for Text. Is there another composable I should use.

[Guy Bieber]

Changing the mutable state does not change the value. This is a pretty basic use case that used to work with Model. Any help would be appreciated.

[romainguy]

Just do Text("my state is ${myValue}"

[romainguy]

Unless I misunderstand what you're trying to achieve

[Guy Bieber]

I am changing myValue and the Text is not recomposing.

[Guy Bieber]

I get a value change over bluetooth and want the new value displayed in a Text element.

[Mark Murphy]

How are you declaring myValue?

[Guy Bieber]

class BasicStatusDataModel<T> (
    ...
    value : T, // wrapped mutable
    ...
) {

    var value by mutableStateOf(value)

[Guy Bieber]

This is ugly but works:

package com.nikolamotor.test

import android.os.Bundle
import android.os.Handler
import androidx.appcompat.app.AppCompatActivity
import androidx.compose.foundation.Text
import androidx.compose.material.MaterialTheme
import androidx.compose.material.Surface
import androidx.compose.runtime.Composable
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.ui.platform.setContent

import com.nikolamotor.test.ui.TestTheme

class MainActivity : AppCompatActivity() {

    class Data (
        count : Int = 0
    ) {
        var count = mutableStateOf(count)
    }

    var data = Data()

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            TestTheme {
                Surface(color = MaterialTheme.colors.background) {
                    Greeting()
                }
            }
        }
        increment()
    }

    fun increment () {
        Handler(this.getMainLooper()).postDelayed({
            data.count.value++
            increment()
        }, 1000)
    }

    @Composable
    fun Greeting() {
        var data = remember { data }
        Text(text = "Hello ${data.count.value}!")
    }
    
}

[Guy Bieber]

Cleaner and also works:

package com.nikolamotor.test

import android.os.Bundle
import android.os.Handler
import androidx.appcompat.app.AppCompatActivity
import androidx.compose.foundation.Text
import androidx.compose.material.MaterialTheme
import androidx.compose.material.Surface
import androidx.compose.runtime.Composable
import androidx.compose.runtime.remember
import androidx.compose.ui.platform.setContent

import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.setValue

import com.nikolamotor.test.ui.TestTheme

class MainActivity : AppCompatActivity() {

    class Data <T> (
        count : T
    ) {
        var count by mutableStateOf(count)
    }

    var data = Data<Int>(0)

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            TestTheme {
                Surface(color = MaterialTheme.colors.background) {
                    Greeting()
                }
            }
        }
        increment()
    }

    fun increment () {
        Handler(this.getMainLooper()).postDelayed({
            data.count++
            increment()
        }, 1000)
    }

    @Composable
    fun Greeting() {
        var data = remember { data }
        Text(text = "Hello ${data.count}!")
    }

}

[romainguy]

In your original code where is the var stored? You may need to remember{} it it’s just declared in a composable function

[Guy Bieber]

The problem I believe is I have compose function that uses remember and then calls another compose function that also does a remember. This seems to not make the child function recompose.

[Guy Bieber]

It would be nice if there was a compiler check for remember such that it wraps something that is mutableStateOf. This definitely makes things trickier.

[Guy Bieber]

Here is what I am doing which doesn’t work:
@Composable
override fun view () {
//var mDataModel = remember {dataModel}
val drawerState = rememberBottomDrawerState(dataModel.drawerState)

BottomDrawerLayout(
drawerState = drawerState,
gesturesEnabled = true,
drawerContent = {
drawerView()
},
bodyContent = {
baseView()
}
)
}

Changing dataModel.drawerState to BottomDrawerValue.Open has no effect.