perf(android): reduce tab-switch CPU churn

apps/android/app/src/main/java/ai/openclaw/app/chat/ChatController.kt

@@ -75,7 +75,7 @@ class ChatController(
   fun load(sessionKey: String) {
     val key = sessionKey.trim().ifEmpty { "main" }
     _sessionKey.value = key
-    scope.launch { bootstrap(forceHealth = true) }
+    scope.launch { bootstrap(forceHealth = true, refreshSessions = true) }
   }
 
   fun applyMainSessionKey(mainSessionKey: String) {
@@ -84,11 +84,11 @@ class ChatController(
     if (_sessionKey.value == trimmed) return
     if (_sessionKey.value != "main") return
     _sessionKey.value = trimmed
-    scope.launch { bootstrap(forceHealth = true) }
+    scope.launch { bootstrap(forceHealth = true, refreshSessions = true) }
   }
 
   fun refresh() {
-    scope.launch { bootstrap(forceHealth = true) }
+    scope.launch { bootstrap(forceHealth = true, refreshSessions = true) }
   }
 
   fun refreshSessions(limit: Int? = null) {
@@ -106,7 +106,9 @@ class ChatController(
     if (key.isEmpty()) return
     if (key == _sessionKey.value) return
     _sessionKey.value = key
-    scope.launch { bootstrap(forceHealth = true) }
+    // Keep the thread switch path lean: history + health are needed immediately,
+    // but the session list is usually unchanged and can refresh on explicit pull-to-refresh.
+    scope.launch { bootstrap(forceHealth = true, refreshSessions = false) }
   }
 
   fun sendMessage(
@@ -249,7 +251,7 @@ class ChatController(
     }
   }
 
-  private suspend fun bootstrap(forceHealth: Boolean) {
+  private suspend fun bootstrap(forceHealth: Boolean, refreshSessions: Boolean) {
     _errorText.value = null
     _healthOk.value = false
     clearPendingRuns()
@@ -271,7 +273,9 @@ class ChatController(
       history.thinkingLevel?.trim()?.takeIf { it.isNotEmpty() }?.let { _thinkingLevel.value = it }
 
       pollHealthIfNeeded(force = forceHealth)
-      fetchSessions(limit = 50)
+      if (refreshSessions) {
+        fetchSessions(limit = 50)
+      }
     } catch (err: Throwable) {
       _errorText.value = err.message
     }

apps/android/app/src/main/java/ai/openclaw/app/ui/CanvasScreen.kt

@@ -25,7 +25,7 @@ import ai.openclaw.app.MainViewModel
 
 @SuppressLint("SetJavaScriptEnabled")
 @Composable
-fun CanvasScreen(viewModel: MainViewModel, modifier: Modifier = Modifier) {
+fun CanvasScreen(viewModel: MainViewModel, visible: Boolean, modifier: Modifier = Modifier) {
   val context = LocalContext.current
   val isDebuggable = (context.applicationInfo.flags and android.content.pm.ApplicationInfo.FLAG_DEBUGGABLE) != 0
   val webViewRef = remember { mutableStateOf<WebView?>(null) }
@@ -45,6 +45,7 @@ fun CanvasScreen(viewModel: MainViewModel, modifier: Modifier = Modifier) {
     modifier = modifier,
     factory = {
       WebView(context).apply {
+        visibility = if (visible) View.VISIBLE else View.INVISIBLE
         settings.javaScriptEnabled = true
         settings.domStorageEnabled = true
         settings.mixedContentMode = WebSettings.MIXED_CONTENT_COMPATIBILITY_MODE
@@ -127,6 +128,16 @@ fun CanvasScreen(viewModel: MainViewModel, modifier: Modifier = Modifier) {
         webViewRef.value = this
       }
     },
+    update = { webView ->
+      webView.visibility = if (visible) View.VISIBLE else View.INVISIBLE
+      if (visible) {
+        webView.resumeTimers()
+        webView.onResume()
+      } else {
+        webView.onPause()
+        webView.pauseTimers()
+      }
+    },
   )
 }
 

apps/android/app/src/main/java/ai/openclaw/app/ui/PostOnboardingTabs.kt

@@ -39,7 +39,9 @@ import androidx.compose.runtime.saveable.rememberSaveable
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
+import androidx.compose.ui.draw.alpha
 import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.zIndex
 import androidx.compose.ui.graphics.vector.ImageVector
 import androidx.compose.ui.platform.LocalDensity
 import androidx.compose.ui.text.font.FontWeight
@@ -68,10 +70,19 @@ private enum class StatusVisual {
 @Composable
 fun PostOnboardingTabs(viewModel: MainViewModel, modifier: Modifier = Modifier) {
   var activeTab by rememberSaveable { mutableStateOf(HomeTab.Connect) }
+  var chatTabStarted by rememberSaveable { mutableStateOf(false) }
+  var screenTabStarted by rememberSaveable { mutableStateOf(false) }
 
-  // Stop TTS when user navigates away from voice tab
+  // Stop TTS when user navigates away from voice tab, and lazily keep the Chat/Screen tabs
+  // alive after the first visit so repeated tab switches do not rebuild their UI trees.
   LaunchedEffect(activeTab) {
     viewModel.setVoiceScreenActive(activeTab == HomeTab.Voice)
+    if (activeTab == HomeTab.Chat) {
+      chatTabStarted = true
+    }
+    if (activeTab == HomeTab.Screen) {
+      screenTabStarted = true
+    }
   }
 
   val statusText by viewModel.statusText.collectAsState()
@@ -120,11 +131,35 @@ fun PostOnboardingTabs(viewModel: MainViewModel, modifier: Modifier = Modifier)
           .consumeWindowInsets(innerPadding)
           .background(mobileBackgroundGradient),
     ) {
+      if (chatTabStarted) {
+        Box(
+          modifier =
+            Modifier
+              .matchParentSize()
+              .alpha(if (activeTab == HomeTab.Chat) 1f else 0f)
+              .zIndex(if (activeTab == HomeTab.Chat) 1f else 0f),
+        ) {
+          ChatSheet(viewModel = viewModel)
+        }
+      }
+
+      if (screenTabStarted) {
+        ScreenTabScreen(
+          viewModel = viewModel,
+          visible = activeTab == HomeTab.Screen,
+          modifier =
+            Modifier
+              .matchParentSize()
+              .alpha(if (activeTab == HomeTab.Screen) 1f else 0f)
+              .zIndex(if (activeTab == HomeTab.Screen) 1f else 0f),
+        )
+      }
+
       when (activeTab) {
         HomeTab.Connect -> ConnectTabScreen(viewModel = viewModel)
-        HomeTab.Chat -> ChatSheet(viewModel = viewModel)
+        HomeTab.Chat -> if (!chatTabStarted) ChatSheet(viewModel = viewModel)
         HomeTab.Voice -> VoiceTabScreen(viewModel = viewModel)
-        HomeTab.Screen -> ScreenTabScreen(viewModel = viewModel)
+        HomeTab.Screen -> Unit
         HomeTab.Settings -> SettingsSheet(viewModel = viewModel)
       }
     }
@@ -132,16 +167,19 @@ fun PostOnboardingTabs(viewModel: MainViewModel, modifier: Modifier = Modifier)
 }
 
 @Composable
-private fun ScreenTabScreen(viewModel: MainViewModel) {
+private fun ScreenTabScreen(viewModel: MainViewModel, visible: Boolean, modifier: Modifier = Modifier) {
   val isConnected by viewModel.isConnected.collectAsState()
-  LaunchedEffect(isConnected) {
-    if (isConnected) {
+  var refreshedForCurrentConnection by rememberSaveable(isConnected) { mutableStateOf(false) }
+
+  LaunchedEffect(isConnected, visible, refreshedForCurrentConnection) {
+    if (visible && isConnected && !refreshedForCurrentConnection) {
       viewModel.refreshHomeCanvasOverviewIfConnected()
+      refreshedForCurrentConnection = true
     }
   }
 
-  Box(modifier = Modifier.fillMaxSize()) {
-    CanvasScreen(viewModel = viewModel, modifier = Modifier.fillMaxSize())
+  Box(modifier = modifier.fillMaxSize()) {
+    CanvasScreen(viewModel = viewModel, visible = visible, modifier = Modifier.fillMaxSize())
   }
 }
 

apps/android/app/src/main/java/ai/openclaw/app/ui/chat/ChatSheetContent.kt

@@ -63,7 +63,6 @@ fun ChatSheetContent(viewModel: MainViewModel) {
 
   LaunchedEffect(mainSessionKey) {
     viewModel.loadChat(mainSessionKey)
-    viewModel.refreshChatSessions(limit = 200)
   }
 
   val context = LocalContext.current