我有一個 Composable，其中需要由 Composable 本身和呼叫方（使用 Composable 的引數）更新記住的值（偏移量）——我該如何實作呢？
特別是，我有以下一段代碼。我正在談論的值是offsetin NavigableBox：我既需要能夠通過拖動框來控制它，也需要使用OffsetInputField作為引數傳遞的值手動設定它。
class MainActivity : ComponentActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContent {
Surface {
Box {
var boxOffset by remember { mutableStateOf(Offset.Zero) }
NavigableBox(boxOffset)
OffsetInputField { offset ->
offset.toFloat().let { boxOffset = Offset(it, it) }
}
}
}
}
}
}
@Composable
fun OffsetInputField(onInput: (String) -> Unit) {
var value by remember { mutableStateOf("") }
TextField(
value = value,
onValueChange = { value = it },
keyboardOptions = KeyboardOptions(imeAction = ImeAction.Go),
keyboardActions = KeyboardActions(onGo = { onInput(value) })
)
}
@Composable
fun NavigableBox(initOffset: Offset) {
var offset by remember(initOffset) { mutableStateOf(initOffset) }
Box(
modifier = Modifier
.fillMaxSize()
.pointerInput(Unit) { detectTransformGestures { _, pan, _, _ -> offset = pan } }
) {
Box(modifier = Modifier
.size(100.dp)
.offset { IntOffset(offset.x.roundToInt(), offset.y.roundToInt()) }
.background(Color.Blue)
)
}
}
在當前實作中，拖動作業正常，直到一個新值作為OffsetInputField' 的輸入傳遞——然后框停止回應拖動。我認為這是因為MutableState包含偏移量的物件在重新計算時發生了變化，并且盒子不再觀察它。
I already tried using unidirectional data flow in NavigableBox (passing offset value and onOffsetChange lambda to it, but then dragging doesn't work as expected: the box just jiggles around its initial position, returning back to it when the gesture stops.
In case anyone interested, I'm developing an app where the draggable box is a map, and the text field is used for searching objects on it: the map is moved to be centered on an object entered.
uj5u.com熱心網友回復：
pointerInput捕獲內部使用的所有狀態變數。使用 newinitOffset您正在創建一個新的可變狀態，但pointerInput會不斷更新舊的參考。
您需要通過將相同的值傳遞給來重新啟動它key：
pointerInput(initOffset) { /*...*/ }
轉載請註明出處，本文鏈接：https://www.uj5u.com/shujuku/438114.html
標籤：android kotlin android-layout android-jetpack-compose