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Commit a030ec32 authored by Chaohui Wang's avatar Chaohui Wang
Browse files

Fix race condition in rememberPageStateFixed 

During screen rotation, currentPage could be updated to a wrong value.

Split the rotation detection and scrolling to correct page to fix this
issue.

Fix: 281928661
Test: Manually with App languages page
Change-Id: I71f69db0c832dc4b4dc90ee210efbfe768cf17e4
parent d516a7ca

packages/SettingsLib/Spa/spa/src/com/android/settingslib/spa/widget/scaffold/SettingsPager.kt

+23 −11
Original line number Diff line number Diff line
@@ -21,14 +21,13 @@ import androidx.compose.foundation.layout.Column 
import androidx.compose.foundation.layout.padding

import androidx.compose.foundation.pager.HorizontalPager

import androidx.compose.foundation.pager.PagerState

import androidx.compose.foundation.pager.rememberPagerState

import androidx.compose.material3.TabRow

import androidx.compose.runtime.Composable

import androidx.compose.runtime.LaunchedEffect

import androidx.compose.runtime.SideEffect

import androidx.compose.runtime.State

import androidx.compose.runtime.getValue

import androidx.compose.runtime.mutableStateOf

import androidx.compose.runtime.remember

import androidx.compose.runtime.rememberCoroutineScope

import androidx.compose.runtime.saveable.rememberSaveable

import androidx.compose.runtime.setValue
@@ -50,7 +49,7 @@ fun SettingsPager(titles: List<String>, content: @Composable (page: Int) -> Unit 


    Column {

        val coroutineScope = rememberCoroutineScope()

        val pagerState by rememberPageStateFixed()

        val pagerState = rememberPageStateFixed()



        TabRow(

            selectedTabIndex = pagerState.currentPage,
@@ -89,17 +88,30 @@ fun SettingsPager(titles: List<String>, content: @Composable (page: Int) -> Unit 
 */

@Composable

@OptIn(ExperimentalFoundationApi::class)

private fun rememberPageStateFixed(): State<PagerState> {

private fun rememberPageStateFixed(): PagerState {

    var currentPage by rememberSaveable { mutableStateOf(0) }

    val pagerStateHolder = remember { mutableStateOf(PagerState(currentPage)) }

    LaunchedEffect(LocalConfiguration.current.orientation) {

    var targetPage by rememberSaveable { mutableStateOf(-1) }

    val pagerState = rememberPagerState()

    val configuration = LocalConfiguration.current

    var lastScreenWidthDp by rememberSaveable { mutableStateOf(-1) }

    val screenWidthDp = configuration.screenWidthDp

    LaunchedEffect(screenWidthDp) {

        // Reset pager state to fix an issue after configuration change.

        // When we declare android:configChanges="orientation" in the manifest, the pager state is

        // in a weird state after configuration change.

        pagerStateHolder.value = PagerState(currentPage)

        // When we declare android:configChanges in the manifest, the pager state is in a weird

        // state after configuration change.

        targetPage = currentPage

        lastScreenWidthDp = screenWidthDp

    }

    LaunchedEffect(targetPage) {

        if (targetPage != -1) {

            pagerState.scrollToPage(targetPage)

            targetPage = -1

        }

    }

    SideEffect {

        currentPage = pagerStateHolder.value.currentPage

        if (lastScreenWidthDp == screenWidthDp) {

            currentPage = pagerState.currentPage

        }

    }

    return pagerStateHolder

    return pagerState

}