Better support for sliding to change model

Android/src/app/src/main/java/com/google/aiedge/gallery/data/Model.kt

@@ -90,6 +90,8 @@ data class Model(
   // The following fields are managed by the app. Don't need to set manually.
   var instance: Any? = null,
   var initializing: Boolean = false,
+  // TODO(jingjin): use a "queue" system to manage model init and cleanup.
+  var cleanUpAfterInit: Boolean = false,
   var configValues: Map<String, Any> = mapOf(),
   var totalBytes: Long = 0L,
   var accessToken: String? = null,

Android/src/app/src/main/java/com/google/aiedge/gallery/ui/common/ModelPageAppBar.kt

@@ -16,26 +16,19 @@
 
 package com.google.aiedge.gallery.ui.common
 
-import androidx.compose.foundation.background
-import androidx.compose.foundation.clickable
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.Row
-import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.layout.size
-import androidx.compose.foundation.shape.CircleShape
 import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.automirrored.rounded.ArrowBack
-import androidx.compose.material.icons.rounded.ArrowDropDown
 import androidx.compose.material.icons.rounded.Settings
 import androidx.compose.material3.CenterAlignedTopAppBar
 import androidx.compose.material3.ExperimentalMaterial3Api
 import androidx.compose.material3.Icon
 import androidx.compose.material3.IconButton
 import androidx.compose.material3.MaterialTheme
-import androidx.compose.material3.ModalBottomSheet
 import androidx.compose.material3.Text
-import androidx.compose.material3.rememberModalBottomSheetState
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.collectAsState
 import androidx.compose.runtime.getValue
@@ -44,7 +37,7 @@ import androidx.compose.runtime.remember
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
-import androidx.compose.ui.draw.clip
+import androidx.compose.ui.draw.alpha
 import androidx.compose.ui.graphics.vector.ImageVector
 import androidx.compose.ui.platform.LocalContext
 import androidx.compose.ui.res.vectorResource
@@ -54,7 +47,6 @@ import com.google.aiedge.gallery.data.Model
 import com.google.aiedge.gallery.data.ModelDownloadStatusType
 import com.google.aiedge.gallery.data.Task
 import com.google.aiedge.gallery.ui.common.chat.ConfigDialog
-import com.google.aiedge.gallery.ui.common.modelitem.StatusIcon
 import com.google.aiedge.gallery.ui.modelmanager.ModelManagerViewModel
 
 @OptIn(ExperimentalMaterial3Api::class)
@@ -69,14 +61,15 @@ fun ModelPageAppBar(
   onConfigChanged: (oldConfigValues: Map<String, Any>, newConfigValues: Map<String, Any>) -> Unit = { _, _ -> },
 ) {
   var showConfigDialog by remember { mutableStateOf(false) }
-  var showModelPicker by remember { mutableStateOf(false) }
   val modelManagerUiState by modelManagerViewModel.uiState.collectAsState()
-  val sheetState = rememberModalBottomSheetState(skipPartiallyExpanded = true)
   val context = LocalContext.current
   val curDownloadStatus = modelManagerUiState.modelDownloadStatus[model.name]
 
   CenterAlignedTopAppBar(title = {
-    Column(horizontalAlignment = Alignment.CenterHorizontally) {
+    Column(
+      horizontalAlignment = Alignment.CenterHorizontally,
+      verticalArrangement = Arrangement.spacedBy(4.dp)
+    ) {
       // Task type.
       Row(
         verticalAlignment = Alignment.CenterVertically,
@@ -95,29 +88,13 @@ fun ModelPageAppBar(
         )
       }
 
-      // Model name.
-      Row(verticalAlignment = Alignment.CenterVertically,
-        horizontalArrangement = Arrangement.spacedBy(2.dp),
-        modifier = Modifier
-          .clip(CircleShape)
-          .background(MaterialTheme.colorScheme.surfaceContainerHigh)
-          .clickable {
-            showModelPicker = true
-          }
-          .padding(start = 8.dp, end = 2.dp)) {
-        StatusIcon(downloadStatus = modelManagerUiState.modelDownloadStatus[model.name])
-        Text(
-          model.name,
-          style = MaterialTheme.typography.labelSmall,
-          modifier = Modifier.padding(start = 4.dp),
+      // Model chips pager.
+      ModelPickerChipsPager(
+        task = task,
+        initialModel = model,
+        modelManagerViewModel = modelManagerViewModel,
+        onModelSelected = onModelSelected,
       )
-        Icon(
-          Icons.Rounded.ArrowDropDown,
-          modifier = Modifier.size(20.dp),
-          contentDescription = "",
-        )
-      }
-
     }
   }, modifier = modifier,
     // The back button.
@@ -131,15 +108,21 @@ fun ModelPageAppBar(
     },
     // The config button for the model (if existed).
     actions = {
-      if (model.configs.isNotEmpty() && curDownloadStatus?.status == ModelDownloadStatusType.SUCCEEDED) {
-        IconButton(onClick = { showConfigDialog = true }) {
+      val showConfigButton =
+        model.configs.isNotEmpty() && curDownloadStatus?.status == ModelDownloadStatusType.SUCCEEDED
+      IconButton(
+        onClick = {
+          showConfigDialog = true
+        },
+        enabled = showConfigButton,
+        modifier = Modifier.alpha(if (showConfigButton) 1f else 0f)
+      ) {
         Icon(
           imageVector = Icons.Rounded.Settings,
           contentDescription = "",
           tint = MaterialTheme.colorScheme.primary
         )
       }
-      }
     })
 
   // Config dialog.
@@ -193,21 +176,4 @@ fun ModelPageAppBar(
       },
     )
   }
-
-  // Model picker.
-  if (showModelPicker) {
-    ModalBottomSheet(
-      onDismissRequest = { showModelPicker = false },
-      sheetState = sheetState,
-    ) {
-      ModelPicker(
-        task = task,
-        modelManagerViewModel = modelManagerViewModel,
-        onModelSelected = { model ->
-          showModelPicker = false
-          onModelSelected(model)
-        }
-      )
-    }
-  }
 }

Android/src/app/src/main/java/com/google/aiedge/gallery/ui/common/ModelPickerChipsPager.kt

@@ -0,0 +1,178 @@
+/*
+ * Copyright 2025 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.aiedge.gallery.ui.common
+
+import androidx.compose.animation.AnimatedVisibility
+import androidx.compose.animation.fadeIn
+import androidx.compose.animation.fadeOut
+import androidx.compose.animation.scaleIn
+import androidx.compose.animation.scaleOut
+import androidx.compose.foundation.background
+import androidx.compose.foundation.clickable
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Row
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.pager.HorizontalPager
+import androidx.compose.foundation.pager.rememberPagerState
+import androidx.compose.foundation.shape.CircleShape
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.rounded.ArrowDropDown
+import androidx.compose.material3.CircularProgressIndicator
+import androidx.compose.material3.ExperimentalMaterial3Api
+import androidx.compose.material3.Icon
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.ModalBottomSheet
+import androidx.compose.material3.Text
+import androidx.compose.material3.rememberModalBottomSheetState
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.collectAsState
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
+import androidx.compose.runtime.rememberCoroutineScope
+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.draw.clip
+import androidx.compose.ui.graphics.graphicsLayer
+import androidx.compose.ui.unit.dp
+import com.google.aiedge.gallery.data.Model
+import com.google.aiedge.gallery.data.Task
+import com.google.aiedge.gallery.ui.common.modelitem.StatusIcon
+import com.google.aiedge.gallery.ui.modelmanager.ModelInitializationStatusType
+import com.google.aiedge.gallery.ui.modelmanager.ModelManagerViewModel
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.launch
+import kotlin.math.absoluteValue
+
+@OptIn(ExperimentalMaterial3Api::class)
+@Composable
+fun ModelPickerChipsPager(
+  task: Task,
+  initialModel: Model,
+  modelManagerViewModel: ModelManagerViewModel,
+  onModelSelected: (Model) -> Unit,
+) {
+  var showModelPicker by remember { mutableStateOf(false) }
+  var modelPickerModel by remember { mutableStateOf<Model?>(null) }
+  val modelManagerUiState by modelManagerViewModel.uiState.collectAsState()
+  val sheetState = rememberModalBottomSheetState(skipPartiallyExpanded = true)
+  val scope = rememberCoroutineScope()
+
+  val pagerState = rememberPagerState(initialPage = task.models.indexOf(initialModel),
+    pageCount = { task.models.size })
+
+  // Sync scrolling.
+  LaunchedEffect(modelManagerViewModel.pagerScrollState) {
+    modelManagerViewModel.pagerScrollState.collect { state ->
+      pagerState.scrollToPage(state.page, state.offset)
+    }
+  }
+
+  HorizontalPager(state = pagerState, userScrollEnabled = false) { pageIndex ->
+    val model = task.models[pageIndex]
+
+    // Calculate the alpha of the current page based on how far they are from the center.
+    val pageOffset =
+      ((pagerState.currentPage - pageIndex) + pagerState.currentPageOffsetFraction).absoluteValue
+    val curAlpha = 1f - (pageOffset * 1.5f).coerceIn(0f, 1f)
+
+    val modelInitializationStatus =
+      modelManagerUiState.modelInitializationStatus[model.name]
+
+    Box(
+      modifier = Modifier
+        .fillMaxWidth()
+        .graphicsLayer { alpha = curAlpha },
+      contentAlignment = Alignment.Center
+    ) {
+      Row(
+        verticalAlignment = Alignment.CenterVertically,
+        horizontalArrangement = Arrangement.spacedBy(2.dp)
+      ) {
+        Row(verticalAlignment = Alignment.CenterVertically,
+          horizontalArrangement = Arrangement.spacedBy(2.dp),
+          modifier = Modifier
+            .clip(CircleShape)
+            .background(MaterialTheme.colorScheme.surfaceContainerHigh)
+            .clickable {
+              modelPickerModel = model
+              showModelPicker = true
+            }
+            .padding(start = 8.dp, end = 2.dp)
+            .padding(vertical = 1.dp)) Inner@{
+          Box(contentAlignment = Alignment.Center, modifier = Modifier.size(18.dp)) {
+            StatusIcon(downloadStatus = modelManagerUiState.modelDownloadStatus[model.name])
+            this@Inner.AnimatedVisibility(
+              visible = modelInitializationStatus?.status == ModelInitializationStatusType.INITIALIZING,
+              enter = scaleIn() + fadeIn(),
+              exit = scaleOut() + fadeOut(),
+            ) {
+              // Circular progress indicator.
+              CircularProgressIndicator(
+                modifier = Modifier
+                  .size(17.dp)
+                  .alpha(0.5f),
+                strokeWidth = 2.dp,
+                color = MaterialTheme.colorScheme.onSurfaceVariant
+              )
+            }
+          }
+          Text(
+            model.name,
+            style = MaterialTheme.typography.labelSmall,
+            modifier = Modifier.padding(start = 4.dp),
+          )
+          Icon(
+            Icons.Rounded.ArrowDropDown,
+            modifier = Modifier.size(20.dp),
+            contentDescription = "",
+          )
+        }
+      }
+    }
+  }
+
+  // Model picker.
+  val curModelPickerModel = modelPickerModel
+  if (showModelPicker && curModelPickerModel != null) {
+    ModalBottomSheet(
+      onDismissRequest = { showModelPicker = false },
+      sheetState = sheetState,
+    ) {
+      ModelPicker(
+        task = task,
+        modelManagerViewModel = modelManagerViewModel,
+        onModelSelected = { selectedModel ->
+          showModelPicker = false
+
+          scope.launch(Dispatchers.Default) {
+            // Scroll to the selected model.
+            pagerState.animateScrollToPage(task.models.indexOf(selectedModel))
+          }
+
+          onModelSelected(selectedModel)
+        }
+      )
+    }
+  }
+}

Android/src/app/src/main/java/com/google/aiedge/gallery/ui/common/chat/ChatPanel.kt

@@ -16,11 +16,6 @@
 
 package com.google.aiedge.gallery.ui.common.chat
 
-import androidx.compose.animation.AnimatedVisibility
-import androidx.compose.animation.fadeIn
-import androidx.compose.animation.fadeOut
-import androidx.compose.animation.scaleIn
-import androidx.compose.animation.scaleOut
 import androidx.compose.foundation.background
 import androidx.compose.foundation.clickable
 import androidx.compose.foundation.gestures.detectTapGestures
@@ -33,7 +28,6 @@ import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.ime
 import androidx.compose.foundation.layout.imePadding
-import androidx.compose.foundation.layout.offset
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.layout.size
 import androidx.compose.foundation.layout.width
@@ -426,16 +420,6 @@ fun ChatPanel(
         }
       }
 
-      // Model initialization in-progress message.
-      this@Column.AnimatedVisibility(
-        visible = modelInitializationStatus?.status == ModelInitializationStatusType.INITIALIZING,
-        enter = scaleIn() + fadeIn(),
-        exit = scaleOut() + fadeOut(),
-        modifier = Modifier.offset(y = 12.dp)
-      ) {
-        ModelInitializationStatusChip()
-      }
-
       SnackbarHost(hostState = snackbarHostState, modifier = Modifier.padding(vertical = 4.dp))
     }
 

Android/src/app/src/main/java/com/google/aiedge/gallery/ui/common/chat/ChatView.kt

@@ -25,14 +25,17 @@ import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.pager.HorizontalPager
 import androidx.compose.foundation.pager.rememberPagerState
-import androidx.compose.material3.ExperimentalMaterial3Api
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Scaffold
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.collectAsState
 import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.remember
 import androidx.compose.runtime.rememberCoroutineScope
+import androidx.compose.runtime.setValue
+import androidx.compose.runtime.snapshotFlow
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.graphics.graphicsLayer
 import androidx.compose.ui.platform.LocalContext
@@ -42,6 +45,7 @@ import com.google.aiedge.gallery.data.ModelDownloadStatusType
 import com.google.aiedge.gallery.data.Task
 import com.google.aiedge.gallery.ui.common.ModelPageAppBar
 import com.google.aiedge.gallery.ui.modelmanager.ModelManagerViewModel
+import com.google.aiedge.gallery.ui.modelmanager.PagerScrollState
 import com.google.aiedge.gallery.ui.preview.PreviewChatModel
 import com.google.aiedge.gallery.ui.preview.PreviewModelManagerViewModel
 import com.google.aiedge.gallery.ui.preview.TASK_TEST1
@@ -84,8 +88,10 @@ fun ChatView(
     pageCount = { task.models.size })
   val context = LocalContext.current
   val scope = rememberCoroutineScope()
+  var navigatingUp by remember { mutableStateOf(false) }
 
   val handleNavigateUp = {
+    navigatingUp = true
     navigateUp()
 
     // clean up all models.
@@ -99,11 +105,13 @@ fun ChatView(
   // Initialize model when model/download state changes.
   val curDownloadStatus = modelManagerUiState.modelDownloadStatus[selectedModel.name]
   LaunchedEffect(curDownloadStatus, selectedModel.name) {
+    if (!navigatingUp) {
       if (curDownloadStatus?.status == ModelDownloadStatusType.SUCCEEDED) {
         Log.d(TAG, "Initializing model '${selectedModel.name}' from ChatView launched effect")
         modelManagerViewModel.initializeModel(context, task = task, model = selectedModel)
       }
     }
+  }
 
   // Update selected model and clean up previous model when page is settled on a model page.
   LaunchedEffect(pagerState.settledPage) {
@@ -118,6 +126,25 @@ fun ChatView(
     modelManagerViewModel.selectModel(curSelectedModel)
   }
 
+  LaunchedEffect(pagerState) {
+    // Collect from the a snapshotFlow reading the currentPage
+    snapshotFlow { pagerState.currentPage }.collect { page ->
+      Log.d(TAG, "Page changed to $page")
+    }
+  }
+
+  // Trigger scroll sync.
+  LaunchedEffect(pagerState) {
+    snapshotFlow {
+      PagerScrollState(
+        page = pagerState.currentPage,
+        offset = pagerState.currentPageOffsetFraction
+      )
+    }.collect { scrollState ->
+      modelManagerViewModel.pagerScrollState.value = scrollState
+    }
+  }
+
   // Handle system's edge swipe.
   BackHandler {
     handleNavigateUp()

Android/src/app/src/main/java/com/google/aiedge/gallery/ui/llmsingleturn/LlmSingleTurnScreen.kt

@@ -18,17 +18,11 @@ package com.google.aiedge.gallery.ui.llmsingleturn
 
 import android.util.Log
 import androidx.activity.compose.BackHandler
-import androidx.compose.animation.AnimatedVisibility
-import androidx.compose.animation.fadeIn
-import androidx.compose.animation.fadeOut
-import androidx.compose.animation.scaleIn
-import androidx.compose.animation.scaleOut
 import androidx.compose.foundation.background
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.calculateStartPadding
 import androidx.compose.foundation.layout.fillMaxSize
-import androidx.compose.foundation.layout.offset
 import androidx.compose.foundation.layout.padding
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Scaffold
@@ -42,6 +36,7 @@ import androidx.compose.runtime.rememberCoroutineScope
 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.platform.LocalContext
 import androidx.compose.ui.platform.LocalLayoutDirection
 import androidx.compose.ui.tooling.preview.Preview
@@ -50,8 +45,6 @@ import com.google.aiedge.gallery.data.ModelDownloadStatusType
 import com.google.aiedge.gallery.ui.ViewModelProvider
 import com.google.aiedge.gallery.ui.common.ModelPageAppBar
 import com.google.aiedge.gallery.ui.common.chat.ModelDownloadStatusInfoPanel
-import com.google.aiedge.gallery.ui.common.chat.ModelInitializationStatusChip
-import com.google.aiedge.gallery.ui.modelmanager.ModelInitializationStatusType
 import com.google.aiedge.gallery.ui.modelmanager.ModelManagerViewModel
 import com.google.aiedge.gallery.ui.preview.PreviewLlmSingleTurnViewModel
 import com.google.aiedge.gallery.ui.preview.PreviewModelManagerViewModel
@@ -116,9 +109,6 @@ fun LlmSingleTurnScreen(
     }
   }
 
-  val modelInitializationStatus =
-    modelManagerUiState.modelInitializationStatus[selectedModel.name]
-
   Scaffold(modifier = modifier, topBar = {
     ModelPageAppBar(
       task = task,
@@ -151,10 +141,14 @@ fun LlmSingleTurnScreen(
       )
 
       // Main UI after model is downloaded.
-      if (curDownloadStatus?.status == ModelDownloadStatusType.SUCCEEDED) {
+      val modelDownloaded = curDownloadStatus?.status == ModelDownloadStatusType.SUCCEEDED
       Box(
         contentAlignment = Alignment.BottomCenter,
-          modifier = Modifier.weight(1f)
+        modifier = Modifier
+          .weight(1f)
+          // Just hide the UI without removing it from the screen so that the scroll syncing
+          // from ResponsePanel still works.
+          .alpha(if (modelDownloaded) 1.0f else 0.0f)
       ) {
         VerticalSplitView(modifier = Modifier.fillMaxSize(),
           topView = {
@@ -176,24 +170,13 @@ fun LlmSingleTurnScreen(
               ResponsePanel(
                 model = selectedModel,
                 viewModel = viewModel,
+                modelManagerViewModel = modelManagerViewModel,
                 modifier = Modifier
                   .fillMaxSize()
                   .padding(bottom = innerPadding.calculateBottomPadding())
               )
             }
           })
-
-          // Model initialization in-progress message.
-          this@Column.AnimatedVisibility(
-            visible = modelInitializationStatus?.status == ModelInitializationStatusType.INITIALIZING,
-            enter = scaleIn() + fadeIn(),
-            exit = scaleOut() + fadeOut(),
-            modifier = Modifier.offset(y = -innerPadding.calculateBottomPadding())
-          ) {
-            ModelInitializationStatusChip()
-          }
-
-        }
       }
     }
   }

Android/src/app/src/main/java/com/google/aiedge/gallery/ui/llmsingleturn/ResponsePanel.kt

@@ -16,6 +16,7 @@
 
 package com.google.aiedge.gallery.ui.llmsingleturn
 
+import android.util.Log
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
@@ -24,6 +25,8 @@ import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.pager.HorizontalPager
+import androidx.compose.foundation.pager.rememberPagerState
 import androidx.compose.foundation.rememberScrollState
 import androidx.compose.foundation.verticalScroll
 import androidx.compose.material.icons.Icons
@@ -45,40 +48,89 @@ import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableIntStateOf
 import androidx.compose.runtime.remember
 import androidx.compose.runtime.setValue
+import androidx.compose.runtime.snapshotFlow
 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.platform.LocalClipboardManager
 import androidx.compose.ui.text.AnnotatedString
-import androidx.compose.ui.tooling.preview.Preview
 import androidx.compose.ui.unit.dp
 import com.google.aiedge.gallery.data.Model
 import com.google.aiedge.gallery.data.TASK_LLM_SINGLE_TURN
 import com.google.aiedge.gallery.ui.common.chat.MarkdownText
 import com.google.aiedge.gallery.ui.common.chat.MessageBodyBenchmarkLlm
 import com.google.aiedge.gallery.ui.common.chat.MessageBodyLoading
-import com.google.aiedge.gallery.ui.theme.GalleryTheme
+import com.google.aiedge.gallery.ui.modelmanager.ModelManagerViewModel
+import com.google.aiedge.gallery.ui.modelmanager.PagerScrollState
 
 private val OPTIONS = listOf("Response", "Benchmark")
 private val ICONS = listOf(Icons.Outlined.AutoAwesome, Icons.Outlined.Timer)
+private const val TAG = "AGResponsePanel"
 
 @OptIn(ExperimentalMaterial3Api::class)
 @Composable
 fun ResponsePanel(
   model: Model,
   viewModel: LlmSingleTurnViewModel,
+  modelManagerViewModel: ModelManagerViewModel,
   modifier: Modifier = Modifier,
 ) {
+  val task = TASK_LLM_SINGLE_TURN
   val uiState by viewModel.uiState.collectAsState()
+  val modelManagerUiState by modelManagerViewModel.uiState.collectAsState()
   val inProgress = uiState.inProgress
   val initializing = uiState.initializing
   val selectedPromptTemplateType = uiState.selectedPromptTemplateType
-  val response = uiState.responsesByModel[model.name]?.get(selectedPromptTemplateType.label) ?: ""
-  val benchmark = uiState.benchmarkByModel[model.name]?.get(selectedPromptTemplateType.label)
   val responseScrollState = rememberScrollState()
   var selectedOptionIndex by remember { mutableIntStateOf(0) }
   val clipboardManager = LocalClipboardManager.current
+  val pagerState = rememberPagerState(
+    initialPage = task.models.indexOf(model),
+    pageCount = { task.models.size })
+
+  // Select the "response" tab when prompt template changes.
+  LaunchedEffect(selectedPromptTemplateType) {
+    selectedOptionIndex = 0
+  }
+
+  // Update selected model and clean up previous model when page is settled on a model page.
+  LaunchedEffect(pagerState.settledPage) {
+    val curSelectedModel = task.models[pagerState.settledPage]
+    Log.d(
+      TAG,
+      "Pager settled on model '${curSelectedModel.name}' from '${model.name}'. Updating selected model."
+    )
+    if (curSelectedModel.name != model.name) {
+      modelManagerViewModel.cleanupModel(task = task, model = model)
+    }
+    modelManagerViewModel.selectModel(curSelectedModel)
+  }
+
+  // Trigger scroll sync.
+  LaunchedEffect(pagerState) {
+    snapshotFlow {
+      PagerScrollState(
+        page = pagerState.currentPage,
+        offset = pagerState.currentPageOffsetFraction
+      )
+    }.collect { scrollState ->
+      modelManagerViewModel.pagerScrollState.value = scrollState
+    }
+  }
+
+  // Scroll pager when selected model changes.
+  LaunchedEffect(modelManagerUiState.selectedModel) {
+    pagerState.animateScrollToPage(task.models.indexOf(model))
+  }
+
+  HorizontalPager(state = pagerState) { pageIndex ->
+    val curPageModel = task.models[pageIndex]
+
+    val response =
+      uiState.responsesByModel[curPageModel.name]?.get(selectedPromptTemplateType.label) ?: ""
+    val benchmark =
+      uiState.benchmarkByModel[curPageModel.name]?.get(selectedPromptTemplateType.label)
 
     // Scroll to bottom when response changes.
     LaunchedEffect(response) {
@@ -87,11 +139,6 @@ fun ResponsePanel(
       }
     }
 
-  // Select the "response" tab when prompt template changes.
-  LaunchedEffect(selectedPromptTemplateType) {
-    selectedOptionIndex = 0
-  }
-
     if (initializing) {
       Box(
         contentAlignment = Alignment.TopStart,
@@ -191,16 +238,5 @@ fun ResponsePanel(
         }
       }
     }
-}
-
-@Preview(showBackground = true)
-@Composable
-fun ResponsePanelPreview() {
-  GalleryTheme {
-    ResponsePanel(
-      model = TASK_LLM_SINGLE_TURN.models[0],
-      viewModel = LlmSingleTurnViewModel(),
-      modifier = Modifier.fillMaxSize()
-    )
   }
 }

Android/src/app/src/main/java/com/google/aiedge/gallery/ui/modelmanager/ModelManagerViewModel.kt

@@ -133,6 +133,11 @@ data class ModelManagerUiState(
   val textInputHistory: List<String> = listOf(),
 )
 
+data class PagerScrollState(
+  val page: Int = 0,
+  val offset: Float = 0f,
+)
+
 /**
  * ViewModel responsible for managing models, their download status, and initialization.
  *
@@ -150,9 +155,12 @@ open class ModelManagerViewModel(
     downloadRepository.getEnqueuedOrRunningWorkInfos()
   protected val _uiState = MutableStateFlow(createUiState())
   val uiState = _uiState.asStateFlow()
+
   val authService = AuthorizationService(context)
   var curAccessToken: String = ""
 
+  var pagerScrollState: MutableStateFlow<PagerScrollState> = MutableStateFlow(PagerScrollState())
+
   init {
     Log.d(TAG, "In-progress worker infos: $inProgressWorkInfos")
 
@@ -269,6 +277,7 @@ open class ModelManagerViewModel(
 
       // Skip if initialization is in progress.
       if (model.initializing) {
+        model.cleanUpAfterInit = false
         Log.d(TAG, "Model '${model.name}' is being initialized. Skipping.")
         return@launch
       }
@@ -299,6 +308,10 @@ open class ModelManagerViewModel(
             model = model,
             status = ModelInitializationStatusType.INITIALIZED,
           )
+          if (model.cleanUpAfterInit) {
+            Log.d(TAG, "Model '${model.name}' needs cleaning up after init.")
+            cleanupModel(task = task, model = model)
+          }
         } else if (error.isNotEmpty()) {
           Log.d(TAG, "Model '${model.name}' failed to initialize")
           updateModelInitializationStatus(
@@ -345,6 +358,7 @@ open class ModelManagerViewModel(
 
   fun cleanupModel(task: Task, model: Model) {
     if (model.instance != null) {
+      model.cleanUpAfterInit = false
       Log.d(TAG, "Cleaning up model '${model.name}'...")
       when (task.type) {
         TaskType.TEXT_CLASSIFICATION -> TextClassificationModelHelper.cleanUp(model = model)
@@ -360,6 +374,12 @@ open class ModelManagerViewModel(
       updateModelInitializationStatus(
         model = model, status = ModelInitializationStatusType.NOT_INITIALIZED
       )
+    } else {
+      // When model is being initialized and we are trying to clean it up at same time, we mark it
+      // to clean up and it will be cleaned up after initialization is done.
+      if (model.initializing) {
+        model.cleanUpAfterInit = true
+      }
     }
   }