Generate subscription QR codes off the UI thread (#6194)

Move subscription QR bitmap generation from the synchronous share callback into the existing ViewModel, running CPU-bound encoding on Dispatchers.Default and exposing the completed bitmap through StateFlow.

Cancel pending result delivery when the dialog is dismissed, a newer share request replaces it, or the ViewModel is cleared. Keep dialog rendering lifecycle-aware and reuse the existing localized failure message when generation returns no bitmap.

Extract only QR generation and dialog-state wiring from local/talkback-all-10. Leave subscription row accessibility, custom actions, update handling, and clipboard sharing unchanged.

V2rayNG/app/src/main/java/com/v2ray/ang/ui/subscription/SubSettingActivity.kt

@@ -1,7 +1,6 @@
 package com.v2ray.ang.ui.subscription
 
 import android.content.Intent
-import android.graphics.Bitmap
 import android.os.Bundle
 import androidx.activity.viewModels
 import androidx.annotation.StringRes
@@ -53,7 +52,6 @@ import com.v2ray.ang.ui.compose.ReorderableListItem
 import com.v2ray.ang.ui.compose.SelectListDialog
 import com.v2ray.ang.ui.compose.SettingsSwitchItem
 import com.v2ray.ang.ui.compose.verticalScrollbar
-import com.v2ray.ang.util.QRCodeDecoder
 import com.v2ray.ang.util.Utils
 import sh.calvin.reorderable.ReorderableItem
 import sh.calvin.reorderable.rememberReorderableLazyListState
@@ -83,7 +81,7 @@ class SubSettingActivity : BaseComponentActivity() {
                 startActivity(Intent(this, SubEditActivity::class.java).putExtra("subId", subId))
             },
             onRemoveSub = { subId -> removeSub(subId) },
-            onShareQRCode = { url -> QRCodeDecoder.createQRCode(url) },
+            onShareQRCode = viewModel::shareQRCode,
             onShareClipboard = { url ->
                 Utils.setClipboard(this, url)
                 toast(getString(R.string.toast_success))
@@ -110,7 +108,7 @@ fun SubSettingScreen(
     onSubUpdate: () -> Unit,
     onEditSub: (String) -> Unit,
     onRemoveSub: (String) -> Unit,
-    onShareQRCode: (String) -> Bitmap?,
+    onShareQRCode: (String) -> Unit,
     onShareClipboard: (String) -> Unit
 ) {
     val subscriptions by viewModel.subsFlow.collectAsStateWithLifecycle()
@@ -119,7 +117,7 @@ fun SubSettingScreen(
     val confirmRemove = MmkvManager.decodeSettingsBool(AppConfig.PREF_CONFIRM_REMOVE, false)
 
     var shareTarget by remember { mutableStateOf<Pair<String, String>?>(null) }
-    var showQRCodeBitmap by remember { mutableStateOf<Bitmap?>(null) }
+    val qrCodeBitmap by viewModel.qrCode.collectAsStateWithLifecycle()
 
     val lazyListState = rememberLazyListState()
     val reorderableState = rememberReorderableLazyListState(lazyListState) { from, to ->
@@ -254,7 +252,7 @@ fun SubSettingScreen(
             onSelected = { action ->
                 shareTarget = null
                 when (action) {
-                    SubscriptionShareAction.QRCode -> showQRCodeBitmap = onShareQRCode(url)
+                    SubscriptionShareAction.QRCode -> onShareQRCode(url)
                     SubscriptionShareAction.Clipboard -> onShareClipboard(url)
                 }
             },
@@ -263,10 +261,10 @@ fun SubSettingScreen(
     }
 
     // QR Code Dialog
-    if (showQRCodeBitmap != null) {
+    if (qrCodeBitmap != null) {
         QRCodeDialog(
-            bitmap = showQRCodeBitmap,
+            bitmap = qrCodeBitmap,
-            onDismiss = { showQRCodeBitmap = null }
+            onDismiss = viewModel::dismissQRCode
         )
     }
 

V2rayNG/app/src/main/java/com/v2ray/ang/ui/subscription/SubscriptionsViewModel.kt

@@ -1,6 +1,8 @@
 package com.v2ray.ang.ui.subscription
 
 import android.app.Application
+import android.graphics.Bitmap
+import androidx.lifecycle.viewModelScope
 import com.v2ray.ang.AppConfig
 import com.v2ray.ang.R
 import com.v2ray.ang.dto.SubscriptionUpdateMessage
@@ -14,14 +16,20 @@ import com.v2ray.ang.handler.SettingsManager
 import com.v2ray.ang.helper.MessageHelper
 import com.v2ray.ang.ui.base.BaseViewModel
 import com.v2ray.ang.util.LogUtil
+import com.v2ray.ang.util.QRCodeDecoder
 import kotlinx.coroutines.CancellationException
 import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.Job
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.asStateFlow
+import kotlinx.coroutines.launch
 import kotlinx.coroutines.withContext
 
 class SubscriptionsViewModel(application: Application) : BaseViewModel(application) {
+    private var qrCodeJob: Job? = null
+    private val _qrCode = MutableStateFlow<Bitmap?>(null)
+    internal val qrCode = _qrCode.asStateFlow()
     private val subscriptions: MutableList<SubscriptionCache> =
         MmkvManager.decodeSubscriptions().toMutableList()
 
@@ -55,6 +63,21 @@ class SubscriptionsViewModel(application: Application) : BaseViewModel(applicati
         _subsFlow.value = subscriptions.toList()
     }
 
+    internal fun shareQRCode(url: String) {
+        dismissQRCode()
+        qrCodeJob = viewModelScope.launch {
+            val bitmap = withContext(Dispatchers.Default) { QRCodeDecoder.createQRCode(url) }
+            if (bitmap == null) toastError(R.string.toast_failure)
+            _qrCode.value = bitmap
+        }
+    }
+
+    internal fun dismissQRCode() {
+        qrCodeJob?.cancel()
+        qrCodeJob = null
+        _qrCode.value = null
+    }
+
     fun move(fromPosition: Int, toPosition: Int) {
         if (subscriptions.moveItem(fromPosition, toPosition)) {
             MmkvManager.encodeSubsList(subscriptions.mapTo(mutableListOf()) { it.guid })