Animate sort group chevrons

app/src/main/java/org/tasks/tasklist/HeaderViewHolder.kt

@@ -2,6 +2,7 @@ package org.tasks.tasklist
 
 import android.content.Context
 import android.view.View
+import android.widget.ImageView
 import android.widget.TextView
 import androidx.recyclerview.widget.RecyclerView
 import com.todoroo.astrid.api.Filter
@@ -12,10 +13,13 @@ class HeaderViewHolder(
         private val context: Context,
         private val locale: Locale,
         view: View,
-        callback: (Long) -> Unit) : RecyclerView.ViewHolder(view) {
-
-    private val header: TextView = view.findViewById(R.id.header)
+        callback: (Long) -> Unit
+) : RecyclerView.ViewHolder(view) {
+    private val title: TextView = view.findViewById(R.id.header)
+    private val chevron: ImageView = view.findViewById(R.id.chevron)
+    private val row = view.findViewById<View>(R.id.header_row)
     private var sortGroup = -1L
+    private var rotation = 0f
 
     fun bind(filter: Filter, sortMode: Int, alwaysDisplayFullDate: Boolean, section: AdapterSection) {
         sortGroup = section.value
@@ -26,17 +30,24 @@ class HeaderViewHolder(
         }
 
         if (header == null) {
-            this.header.visibility = View.GONE
+            row.visibility = View.GONE
         } else {
-            this.header.visibility = View.VISIBLE
-            this.header.text = header
-            this.header.setCompoundDrawablesRelativeWithIntrinsicBounds(0, 0, if (section.collapsed) R.drawable.ic_keyboard_arrow_down_black_18dp else R.drawable.ic_keyboard_arrow_up_black_18dp, 0)
-            this.header.setTextColor(section.headerColor(context, sortMode))
+            row.visibility = View.VISIBLE
+            this.title.text = header
+            this.title.setTextColor(section.headerColor(context, sortMode))
+            rotation = if (section.collapsed) 180f else 0f
+            chevron.rotation = rotation
         }
     }
 
+    private fun rotate() {
+        rotation = if (rotation == 0f) 180f else 0f
+        chevron.animate().rotation(rotation).setDuration(250).start()
+    }
+
     init {
-        header.setOnClickListener {
+        row.setOnClickListener {
+            rotate()
             callback(sortGroup)
         }
     }

app/src/main/res/layout/task_adapter_header.xml

@@ -1,16 +1,31 @@
 <?xml version="1.0" encoding="utf-8"?>
-<TextView xmlns:android="http://schemas.android.com/apk/res/android"
-  xmlns:app="http://schemas.android.com/apk/res-auto"
-  android:id="@+id/header"
-  style="@style/TextAppearance"
-  android:layout_width="match_parent"
-  android:layout_height="wrap_content"
-  android:background="?attr/selectableItemBackground"
-  android:padding="@dimen/keyline_first"
-  android:gravity="start|center_vertical"
-  android:textColor="@color/text_secondary"
-  android:textSize="@dimen/sku_details_row_text_size"
-  android:drawableEnd="@drawable/ic_keyboard_arrow_down_black_18dp"
-  android:drawableTint="@color/text_tertiary"
-  app:fontFamily="sans-serif-medium" />
+<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    android:id="@+id/header_row"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:background="?attr/selectableItemBackground">
 
+    <TextView
+        android:id="@+id/header"
+        style="@style/TextAppearance"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:layout_alignParentStart="true"
+        android:layout_toStartOf="@id/chevron"
+        android:gravity="start|center_vertical"
+        android:padding="@dimen/keyline_first"
+        android:textColor="@color/text_secondary"
+        android:textSize="@dimen/sku_details_row_text_size"
+        app:fontFamily="sans-serif-medium" />
+
+    <ImageView
+        android:id="@+id/chevron"
+        android:layout_alignParentEnd="true"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:padding="@dimen/keyline_first"
+        android:src="@drawable/ic_keyboard_arrow_down_black_24dp"
+        app:tint="@color/text_tertiary" />
+
+</RelativeLayout>