AnimatedTopAppBar: New custom content option, to also change scrollable color for content below.

app/src/main/java/ua/acclorite/book_story/presentation/components/AnimatedTopAppBar.kt

@@ -1,16 +1,17 @@
 package ua.acclorite.book_story.presentation.components
 
-import androidx.compose.animation.core.FastOutLinearInEasing
 import androidx.compose.animation.core.Spring
+import androidx.compose.animation.core.animateFloatAsState
 import androidx.compose.animation.core.spring
 import androidx.compose.animation.fadeIn
 import androidx.compose.animation.fadeOut
 import androidx.compose.foundation.background
 import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.ColumnScope
 import androidx.compose.foundation.layout.RowScope
 import androidx.compose.foundation.layout.WindowInsets
 import androidx.compose.foundation.layout.fillMaxWidth
-import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.layout.statusBars
 import androidx.compose.material3.ExperimentalMaterial3Api
 import androidx.compose.material3.MaterialTheme
@@ -18,12 +19,11 @@ import androidx.compose.material3.TopAppBar
 import androidx.compose.material3.TopAppBarDefaults
 import androidx.compose.material3.TopAppBarScrollBehavior
 import androidx.compose.runtime.Composable
-import androidx.compose.runtime.remember
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.graphics.lerp
-import androidx.compose.ui.platform.LocalDensity
-import androidx.compose.ui.unit.dp
+import androidx.compose.ui.res.stringResource
+import ua.acclorite.book_story.R
 
 /**
  * Animated top app bar.
@@ -36,6 +36,7 @@ import androidx.compose.ui.unit.dp
  * @param content1Visibility Whether first top app bar should be shown.
  * @param content2Visibility Whether second top app bar should be shown.
  * @param content3Visibility Whether third top app bar should be shown.
+ * @param customContent Custom content below [TopAppBar].
  */
 @OptIn(ExperimentalMaterial3Api::class)
 @Composable
@@ -59,38 +60,28 @@ fun AnimatedTopAppBar(
     content3Visibility: Boolean? = null,
     content3NavigationIcon: @Composable () -> Unit = {},
     content3Title: @Composable () -> Unit = {},
-    content3Actions: @Composable RowScope.() -> Unit = {}
+    content3Actions: @Composable RowScope.() -> Unit = {},
+
+    customContent: @Composable ColumnScope.() -> Unit = {}
+) {
+    val animatedContainerColor = lerp(
+        containerColor,
+        scrolledContainerColor,
+        animateFloatAsState(
+            if (isTopBarScrolled == true) 1f else 0f,
+            animationSpec = spring(
+                stiffness = Spring.StiffnessMediumLow
+            ),
+            label = stringResource(id = R.string.top_app_bar_anim_content_desc)
+        ).value
+    )
+
+    Column(
+        Modifier
+            .fillMaxWidth()
+            .background(animatedContainerColor)
     ) {
         Box(modifier = Modifier.fillMaxWidth()) {
-        val density = LocalDensity.current
-        val statusBarPadding = with(density) {
-            WindowInsets.statusBars.getTop(density).toDp()
-        }
-
-        if (containerColor.alpha != 0f) {
-            Box(
-                modifier = Modifier
-                    .fillMaxWidth()
-                    .height(64.dp + statusBarPadding)
-                    .background(
-                        if (isTopBarScrolled == true) scrolledContainerColor
-                        else containerColor
-                    )
-            )
-        }
-
-        val animatedContainerColor = remember(
-            containerColor,
-            scrolledContainerColor,
-            isTopBarScrolled
-        ) {
-            lerp(
-                containerColor,
-                scrolledContainerColor,
-                FastOutLinearInEasing.transform(if (isTopBarScrolled == true) 1f else 0f)
-            )
-        }
-
             CustomAnimatedVisibility(
                 visible = content1Visibility ?: true,
                 enter = fadeIn(spring(stiffness = Spring.StiffnessMediumLow)),
@@ -104,7 +95,8 @@ fun AnimatedTopAppBar(
                     scrollBehavior = scrollBehavior,
                     modifier = Modifier.fillMaxWidth(),
                     colors = TopAppBarDefaults.topAppBarColors(
-                    containerColor = animatedContainerColor,
+                        containerColor = if (isTopBarScrolled != null) Color.Transparent
+                        else containerColor,
                         scrolledContainerColor = scrolledContainerColor
                     )
                 )
@@ -124,7 +116,8 @@ fun AnimatedTopAppBar(
                         scrollBehavior = scrollBehavior,
                         modifier = Modifier.fillMaxWidth(),
                         colors = TopAppBarDefaults.topAppBarColors(
-                        containerColor = animatedContainerColor,
+                            containerColor = if (isTopBarScrolled != null) Color.Transparent
+                            else containerColor,
                             scrolledContainerColor = scrolledContainerColor
                         )
                     )
@@ -145,13 +138,16 @@ fun AnimatedTopAppBar(
                         scrollBehavior = scrollBehavior,
                         modifier = Modifier.fillMaxWidth(),
                         colors = TopAppBarDefaults.topAppBarColors(
-                        containerColor = animatedContainerColor,
+                            containerColor = if (isTopBarScrolled != null) Color.Transparent
+                            else containerColor,
                             scrolledContainerColor = scrolledContainerColor
                         )
                     )
                 }
             }
         }
+        customContent()
+    }
 }
 
 

app/src/main/java/ua/acclorite/book_story/presentation/screens/library/components/LibraryTabRow.kt

@@ -33,12 +33,14 @@ import ua.acclorite.book_story.presentation.screens.library.data.LibraryEvent
  * Tab row, either scrollable or static, depends on screen width.
  *
  * @param onEvent Event used to Scroll to Page.
+ * @param itemCountBackgroundColor Item count background color.
  * @param books The list of all books.
  * @param pagerState [PagerState].
  */
 @Composable
 fun LibraryTabRow(
     onEvent: (LibraryEvent) -> Unit,
+    itemCountBackgroundColor: Color,
     books: List<CategorizedBooks>,
     pagerState: PagerState
 ) {
@@ -113,7 +115,7 @@ fun LibraryTabRow(
                                 text = tabItem.second.toString(),
                                 modifier = Modifier
                                     .background(
-                                        MaterialTheme.colorScheme.surfaceContainer,
+                                        itemCountBackgroundColor,
                                         MaterialTheme.shapes.medium
                                     )
                                     .padding(horizontal = 8.dp, vertical = 4.dp),

app/src/main/java/ua/acclorite/book_story/presentation/screens/library/components/LibraryTopBar.kt

@@ -1,5 +1,8 @@
 package ua.acclorite.book_story.presentation.screens.library.components
 
+import androidx.compose.animation.animateColorAsState
+import androidx.compose.animation.core.Spring
+import androidx.compose.animation.core.spring
 import androidx.compose.foundation.background
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.Row
@@ -168,12 +171,20 @@ fun LibraryTopBar(
             },
             content3Actions = {
                 MoreDropDown()
-            }
-        )
+            },
+            customContent = {
                 LibraryTabRow(
                     onEvent = onEvent,
                     books = state.value.categorizedBooks,
+                    itemCountBackgroundColor = animateColorAsState(
+                        if (state.value.hasSelectedItems) MaterialTheme.colorScheme.surfaceContainerHighest
+                        else MaterialTheme.colorScheme.surfaceContainer,
+                        animationSpec = spring(stiffness = Spring.StiffnessMediumLow),
+                        label = stringResource(id = R.string.top_app_bar_anim_content_desc)
+                    ).value,
                     pagerState = pagerState
                 )
             }
+        )
+    }
 }