I cant get the Card
in the LazyColumn
to check if the number is in val guestNumbers
and then change the color on the Card
.
But the numbers in val guestNumbers
changes on startup.
Is the Card
the right stuff to use or should i use buttons?
class MainActivity : ComponentActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContent {
val guestNumbers = rememberSaveable {
mutableStateOf(mutableSetOf<Int>(10,11,2,22))
}
NumberGuessingGameTheme {
Scaffold(
topBar = {
TopAppBar {
}
}
) {
Row(modifier = Modifier.fillMaxSize()
) {
Box(
modifier = Modifier
.fillMaxSize()
.weight(4f)
.background(color = Color.LightGray)
) {
Text(
text = "1F",
style = MaterialTheme.typography.caption
)
}
Box(
modifier = Modifier
.fillMaxSize()
.weight(1f)
.background(color = Color.LightGray)
) {
LazyColumn {
items(1000 1) {
Card(modifier = Modifier
.fillMaxSize()
.padding(5.dp)
//.background(if ("$it".toInt() !in guestNumbers.value) Color.Green else Color.Red)
.clickable {
guestNumbers.value.add("$it".toInt())
Log.d("Tag", "${guestNumbers.value}")
},
elevation = 10.dp,
backgroundColor = if ("$it".toInt() in guestNumbers.value) Color.Red else Color.LightGray
) {
Text(text = "$it", fontSize = 28.sp, textAlign = TextAlign.Center)
}
}
}
}
}
}
}
}
}
}
CodePudding user response:
mutableStateOf
cannot track changes of the underlaying object. It can only trigger recomposition when you replace its value with an other object.
You can store an immutable set, create a modifiable copy to change it, and set the new value to your mutable state. This will create a new object.
var guestNumbers by rememberSaveable {
mutableStateOf(setOf(10,11,2,22))
}
Button({
val mutableSet = guestNumbers.toMutableSet()
mutableSet.add(if (Random.nextBoolean()) 2 else Random.nextInt())
guestNumbers = mutableSet.toSet()
}) {
Text(guestNumbers.toString())
}
Note, that if you'll face same problem with a list, you gonna need to call .toImmutableList()
, because .toList()
is only erasing the type and not actually creating a new object if called on a mutable list.