rememberSaveableStateHolder

rememberSaveableStateHolder.kt

package com.hoc081098.kmpviewmodelsample.android

import androidx.compose.foundation.layout.Arrangement
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.Row
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.material3.Button
import androidx.compose.material3.Text
import androidx.compose.runtime.Composable
import androidx.compose.runtime.DisposableEffect
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.saveable.rememberSaveable
import androidx.compose.runtime.saveable.rememberSaveableStateHolder
import androidx.compose.runtime.setValue
import androidx.compose.ui.Modifier

@Composable
fun <T : Any> Navigation(
  currentScreen: T,
  modifier: Modifier = Modifier,
  content: @Composable (T) -> Unit
) {
  // create SaveableStateHolder.
  val saveableStateHolder = rememberSaveableStateHolder()
  Box(modifier) {
    // Wrap the content representing the `currentScreen` inside `SaveableStateProvider`.
    // Here you can also add a screen switch animation like Crossfade where during the
    // animation multiple screens will be displayed at the same time.
    saveableStateHolder.SaveableStateProvider(currentScreen) {
      content(currentScreen)
    }
  }
}

@Composable
fun Demo123Screen() {
  Column {
    var screen by rememberSaveable { mutableStateOf("screen1") }
    Row(horizontalArrangement = Arrangement.SpaceEvenly) {
      Button(onClick = { screen = "screen1" }) {
        Text("Go to screen1")
      }
      Button(onClick = { screen = "screen2" }) {
        Text("Go to screen2")
      }
    }
    Navigation(screen, Modifier.fillMaxSize()) { currentScreen ->
      if (screen == "screen1") {
        Screen1()
      } else {
        Screen2()
      }
    }
  }
}

@Composable
fun Screen1() {
  DisposableEffect(Unit) {
    onDispose {
      println("Screen1 disposed")
    }
  }

  var count by rememberSaveable { mutableStateOf(0) }
  Column {
    Text(text = "Screen1: count=$count")

    // increase button
    Button(onClick = { count++ }) {
      Text("Increase")
    }
  }
}

@Composable
fun Screen2() {
  DisposableEffect(Unit) {
    onDispose {
      println("Screen2 disposed")
    }
  }

  var count by rememberSaveable { mutableStateOf(0) }
  Column {
    Text(text = "Screen2: count=$count")

    // increase button
    Button(onClick = { count++ }) {
      Text("Increase")
    }
  }
}