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androidkotlinuser-interfacecomposable

How do I make kotlin composable update when a global value changes

I am learning the basics of Kotlin and Composables. My use case is very simple, I have a global variable:

var globalValue : Int = 1

Then I have this composable:

@Composable
fun SomeView(modifier: Modifier = Modifier) {
  ...some Text() printing globalValue

When I change the value of the globalValue I would like SomeView() to get called.

I have tried the by remember and using the globalValue as parameter to the Composable, but I seem to miss the point, nothing gets updated.

Any help is appreciated!

Solution

  • You should use State to update the composable when the value of the variable changes, So you can simply use mutableStateOf like below:

    val globalValue = mutableStateOf(1)

    So you need read and write to this state using value property for example to set this variable to 10 you can write this:

    globalValue.value = 10

    if you want to use your globalVariable without calling .value you can simply use delegation for the property using by keyword.

    var globalValue by mutableStateOf(1)

    Now you can set the variable as an normal Int variable.