Address review comments

* Introduce gradle plugin for firebase perf
* Create TrackScrollJank composable to mask tracking code

app/build.gradle.kts

@@ -24,7 +24,7 @@ plugins {
     id("jacoco")
     id("dagger.hilt.android.plugin")
     id("nowinandroid.spotless")
-    id("com.google.firebase.firebase-perf") version "1.4.1"
+    id("nowinandroid.firebase-perf")
 }
 
 android {

app/src/main/java/com/google/samples/apps/nowinandroid/MainActivity.kt

@@ -31,12 +31,12 @@ import javax.inject.Inject
 @AndroidEntryPoint
 class MainActivity : ComponentActivity() {
 
+    /**
+     * Lazily inject [JankStats], which is used to track jank throughout the app.
+     */
     @Inject
     lateinit var lazyStats: dagger.Lazy<JankStats>
 
-    @Inject
-    lateinit var jankFrameListener: JankStats.OnFrameListener
-
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
 
@@ -51,15 +51,11 @@ class MainActivity : ComponentActivity() {
 
     override fun onResume() {
         super.onResume()
-        isTrackingEnabled(true)
+        lazyStats.get().isTrackingEnabled = true
     }
 
     override fun onPause() {
         super.onPause()
-        isTrackingEnabled(false)
-    }
-
-    private fun isTrackingEnabled(enabled: Boolean) {
-        lazyStats.get().isTrackingEnabled = enabled
+        lazyStats.get().isTrackingEnabled = false
     }
 }

app/src/main/java/com/google/samples/apps/nowinandroid/ui/NiaApp.kt

@@ -67,7 +67,6 @@ import com.google.samples.apps.nowinandroid.navigation.TopLevelDestination
 fun NiaApp(windowSizeClass: WindowSizeClass) {
     NiaTheme {
         val navController = rememberNavController()
-
         val niaTopLevelNavigation = remember(navController) {
             NiaTopLevelNavigation(navController)
         }

build-logic/convention/build.gradle.kts

@@ -69,5 +69,9 @@ gradlePlugin {
             id = "nowinandroid.spotless"
             implementationClass = "SpotlessConventionPlugin"
         }
+        register("firebase-perf") {
+            id = "nowinandroid.firebase-perf"
+            implementationClass = "FirebasePerfConventionPlugin"
+        }
     }
 }

build-logic/convention/src/main/kotlin/FirebasePerfConventionPlugin.kt

@@ -0,0 +1,29 @@
+/*
+ * Copyright 2022 The Android Open Source Project
+ *
+ *   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
+ *
+ *       https://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.
+ */
+
+import org.gradle.api.Plugin
+import org.gradle.api.Project
+
+class FirebasePerfConventionPlugin : Plugin<Project> {
+    override fun apply(target: Project) {
+        with(target) {
+            pluginManager.findPlugin("com.google.firebase.firebase-perf").apply {
+                version = "1.4.1"
+            }
+        }
+    }
+
+}

core-ui/src/main/java/com/google/samples/apps/nowinandroid/core/ui/JankStatsExtensions.kt

@@ -16,12 +16,14 @@
 
 package com.google.samples.apps.nowinandroid.core.ui
 
+import androidx.compose.foundation.gestures.ScrollableState
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.DisposableEffect
 import androidx.compose.runtime.DisposableEffectResult
 import androidx.compose.runtime.DisposableEffectScope
 import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.remember
+import androidx.compose.runtime.snapshotFlow
 import androidx.compose.ui.platform.LocalView
 import androidx.metrics.performance.PerformanceMetricsState
 import androidx.metrics.performance.PerformanceMetricsState.MetricsStateHolder
@@ -71,3 +73,18 @@ fun JankMetricDisposableEffect(
         reportMetric(this, metrics)
     }
 }
+
+@Composable
+fun TrackScrollJank(scrollableState: ScrollableState, stateName: String) {
+    JankMetricEffect(scrollableState) { metricsHolder ->
+        snapshotFlow { scrollableState.isScrollInProgress }.collect { isScrollInProgress ->
+            metricsHolder.state?.apply {
+                if (isScrollInProgress) {
+                    addState(stateName, "Scrolling=true")
+                } else {
+                    removeState(stateName)
+                }
+            }
+        }
+    }
+}

feature-foryou/src/main/java/com/google/samples/apps/nowinandroid/feature/foryou/AuthorsCarousel.kt

@@ -38,7 +38,6 @@ import androidx.compose.material3.Surface
 import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.remember
-import androidx.compose.runtime.snapshotFlow
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clip
@@ -57,9 +56,7 @@ import com.google.samples.apps.nowinandroid.core.designsystem.icon.NiaIcons
 import com.google.samples.apps.nowinandroid.core.designsystem.theme.NiaTheme
 import com.google.samples.apps.nowinandroid.core.model.data.Author
 import com.google.samples.apps.nowinandroid.core.model.data.FollowableAuthor
-import com.google.samples.apps.nowinandroid.core.ui.JankMetricEffect
-import kotlinx.coroutines.flow.collect
-import kotlinx.coroutines.flow.combine
+import com.google.samples.apps.nowinandroid.core.ui.TrackScrollJank
 
 @Composable
 fun AuthorsCarousel(
@@ -69,21 +66,7 @@ fun AuthorsCarousel(
 ) {
     val lazyListState = rememberLazyListState()
 
-    JankMetricEffect(lazyListState) { metricsHolder ->
-        combine(
-            snapshotFlow { lazyListState.isScrollInProgress },
-            snapshotFlow { lazyListState.firstVisibleItemIndex }
-        ) { isScrollInProgress, firstVisibleItemIndex ->
-            if (isScrollInProgress) {
-                metricsHolder.state?.addState(
-                    "ForYou:AuthorsCarousel:Scrolling",
-                    "Index=$firstVisibleItemIndex"
-                )
-            } else {
-                metricsHolder.state?.removeState("ForYou:AuthorsCarousel:Scrolling")
-            }
-        }.collect()
-    }
+    TrackScrollJank(lazyListState, "ForYou:AuthorsCarousel")
 
     LazyRow(modifier, lazyListState) {
         items(items = authors, key = { item -> item.author.id }) { followableAuthor ->

feature-foryou/src/main/java/com/google/samples/apps/nowinandroid/feature/foryou/ForYouScreen.kt

@@ -63,7 +63,6 @@ import androidx.compose.material3.windowsizeclass.WindowWidthSizeClass
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.collectAsState
 import androidx.compose.runtime.getValue
-import androidx.compose.runtime.snapshotFlow
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.graphics.Color
@@ -93,11 +92,9 @@ import com.google.samples.apps.nowinandroid.core.model.data.SaveableNewsResource
 import com.google.samples.apps.nowinandroid.core.model.data.previewAuthors
 import com.google.samples.apps.nowinandroid.core.model.data.previewNewsResources
 import com.google.samples.apps.nowinandroid.core.model.data.previewTopics
-import com.google.samples.apps.nowinandroid.core.ui.JankMetricEffect
 import com.google.samples.apps.nowinandroid.core.ui.NewsResourceCardExpanded
+import com.google.samples.apps.nowinandroid.core.ui.TrackScrollJank
 import kotlin.math.floor
-import kotlinx.coroutines.flow.collect
-import kotlinx.coroutines.flow.combine
 
 @Composable
 fun ForYouRoute(
@@ -168,21 +165,7 @@ fun ForYouScreen(
                 }
 
                 val lazyListState = rememberLazyListState()
-                JankMetricEffect(lazyListState) { metricsHolder ->
-                    combine(
-                        snapshotFlow { lazyListState.isScrollInProgress },
-                        snapshotFlow { lazyListState.firstVisibleItemIndex },
-                    ) { isScrollInProgress, firstVisibleItemIndex ->
-                        if (isScrollInProgress) {
-                            metricsHolder.state?.addState(
-                                "ForYou:Feed:Scrolling",
-                                "index=$firstVisibleItemIndex"
-                            )
-                        } else {
-                            metricsHolder.state?.removeState("ForYou:Feed:Scrolling")
-                        }
-                    }.collect()
-                }
+                TrackScrollJank(lazyListState, "ForYou:Feed")
 
                 LazyColumn(
                     state = lazyListState,
@@ -311,21 +294,8 @@ private fun TopicSelection(
     modifier: Modifier = Modifier
 ) {
     val lazyGridState = rememberLazyGridState()
-    JankMetricEffect(lazyGridState) { metricsHolder ->
-        combine(
-            snapshotFlow { lazyGridState.isScrollInProgress },
-            snapshotFlow { lazyGridState.firstVisibleItemIndex },
-        ) { isScrollInProgress, firstVisibleItemIndex ->
-            if (isScrollInProgress) {
-                metricsHolder.state?.addState(
-                    "ForYou:TopicSelection:Scrolling",
-                    "index=$firstVisibleItemIndex"
-                )
-            } else {
-                metricsHolder.state?.removeState("ForYou:TopicSelection:Scrolling")
-            }
-        }.collect()
-    }
+
+    TrackScrollJank(scrollableState = lazyGridState, stateName = "ForYou:TopicSelection")
 
     LazyHorizontalGrid(
         state = lazyGridState,