Improved RecyclerViewHeaderDecoration to make it sticky

app/src/main/java/org/linphone/ui/main/calls/adapter/ContactsAndSuggestionsListAdapter.kt

@@ -13,8 +13,10 @@ import androidx.recyclerview.widget.ListAdapter
 import androidx.recyclerview.widget.RecyclerView
 import org.linphone.R
 import org.linphone.databinding.CallSuggestionListCellBinding
+import org.linphone.databinding.CallSuggestionListDecorationBinding
 import org.linphone.databinding.ContactListCellBinding
 import org.linphone.ui.main.calls.model.ContactOrSuggestionModel
+import org.linphone.utils.AppUtils
 import org.linphone.utils.Event
 import org.linphone.utils.HeaderAdapter
 
@@ -43,12 +45,18 @@ class ContactsAndSuggestionsListAdapter(
             }
             val previousModel = getItem(position - 1)
             return previousModel.friend != null
-        }
+        } else if (position == 0) return true
         return false
     }
 
     override fun getHeaderViewForPosition(context: Context, position: Int): View {
-        return LayoutInflater.from(context).inflate(R.layout.call_suggestion_list_decoration, null)
+        val binding = CallSuggestionListDecorationBinding.inflate(LayoutInflater.from(context))
+        binding.header.text = if (position == 0) {
+            AppUtils.getString(R.string.call_start_contacts_list_title)
+        } else {
+            AppUtils.getString(R.string.call_start_suggestions_list_title)
+        }
+        return binding.root
     }
 
     override fun getItemViewType(position: Int): Int {

app/src/main/java/org/linphone/ui/main/calls/fragment/StartCallFragment.kt

@@ -108,7 +108,7 @@ class StartCallFragment : GenericFragment() {
         binding.contactsAndSuggestionsList.setHasFixedSize(true)
         binding.contactsAndSuggestionsList.adapter = adapter
 
-        val headerItemDecoration = RecyclerViewHeaderDecoration(requireContext(), adapter)
+        val headerItemDecoration = RecyclerViewHeaderDecoration(requireContext(), adapter, true)
         binding.contactsAndSuggestionsList.addItemDecoration(headerItemDecoration)
 
         adapter.contactClickedEvent.observe(viewLifecycleOwner) {

app/src/main/java/org/linphone/utils/RecyclerViewHeaderDecoration.kt

@@ -27,7 +27,11 @@ import android.view.View
 import android.view.ViewGroup
 import androidx.recyclerview.widget.RecyclerView
 
-class RecyclerViewHeaderDecoration(private val context: Context, private val adapter: HeaderAdapter) : RecyclerView.ItemDecoration() {
+class RecyclerViewHeaderDecoration(
+    private val context: Context,
+    private val adapter: HeaderAdapter,
+    private val sticky: Boolean = false
+) : RecyclerView.ItemDecoration() {
     private val headers: SparseArray<View> = SparseArray()
 
     override fun getItemOffsets(
@@ -74,8 +78,12 @@ class RecyclerViewHeaderDecoration(private val context: Context, private val ada
     }
 
     override fun onDraw(canvas: Canvas, parent: RecyclerView, state: RecyclerView.State) {
-        for (i in 0 until parent.childCount) {
+        if (sticky) return
+
+        // Used to display the moving item decoration
+        for (i in 0 until parent.childCount) { // Only returns visible children
             val child = parent.getChildAt(i)
+            // Maps the visible view position to the item index in the adapter
             val position = parent.getChildAdapterPosition(child)
             if (position != RecyclerView.NO_POSITION && adapter.displayHeaderForPosition(position)) {
                 canvas.save()
@@ -89,6 +97,62 @@ class RecyclerViewHeaderDecoration(private val context: Context, private val ada
             }
         }
     }
+
+    override fun onDrawOver(canvas: Canvas, parent: RecyclerView, state: RecyclerView.State) {
+        if (!sticky) return
+
+        var latestPositionHeaderFound = -1
+        var nextHeaderTopPosition = -1f
+
+        for (index in parent.childCount downTo 0) {
+            val child = parent.getChildAt(index)
+            val position = parent.getChildAdapterPosition(child)
+            if (position != RecyclerView.NO_POSITION && adapter.displayHeaderForPosition(position)) {
+                canvas.save()
+                val headerView: View = headers.get(position) ?: adapter.getHeaderViewForPosition(
+                    context,
+                    position
+                )
+
+                val top = child.y - headerView.height
+                if (top >= 0) { // don't move the first header
+                    canvas.translate(0f, top)
+                }
+
+                headerView.draw(canvas)
+                canvas.restore()
+
+                latestPositionHeaderFound = position
+                nextHeaderTopPosition = child.y
+            }
+        }
+
+        // Makes sure at least one header is displayed
+        if (latestPositionHeaderFound > 0 || latestPositionHeaderFound == -1) {
+            // Display first item header at top
+            val topVisibleChild = parent.getChildAt(0)
+            val topVisibleChildPosition = parent.getChildAdapterPosition(topVisibleChild)
+            for (position in topVisibleChildPosition downTo 0) {
+                if (adapter.displayHeaderForPosition(position)) {
+                    canvas.save()
+                    val headerView: View = headers.get(position) ?: adapter.getHeaderViewForPosition(
+                        context,
+                        position
+                    )
+
+                    // Do not translate it as we want it sticky to the top unless in contact with next header
+                    if (nextHeaderTopPosition > 0 && nextHeaderTopPosition <= (headerView.height * 2)) {
+                        val top = nextHeaderTopPosition - (headerView.height * 2)
+                        canvas.translate(0f, top)
+                    }
+
+                    headerView.draw(canvas)
+                    canvas.restore()
+                    break
+                }
+            }
+        }
+    }
 }
 
 interface HeaderAdapter {

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

@@ -185,24 +185,6 @@
                 app:layout_constraintStart_toStartOf="parent"
                 app:layout_constraintTop_toBottomOf="@id/no_contacts_nor_suggestion_image" />
 
-            <androidx.appcompat.widget.AppCompatTextView
-                style="@style/section_header_style"
-                android:id="@+id/contacts_and_suggestions_label"
-                android:layout_width="0dp"
-                android:layout_height="wrap_content"
-                android:layout_marginStart="16dp"
-                android:layout_marginTop="16dp"
-                android:layout_marginEnd="16dp"
-                android:padding="5dp"
-                android:text="@string/call_start_contacts_list_title"
-                android:visibility="@{viewModel.contactsAndSuggestionsList.size() == 0 ? View.GONE : View.VISIBLE}"
-                app:layout_constraintVertical_chainStyle="packed"
-                app:layout_constraintVertical_bias="0"
-                app:layout_constraintStart_toStartOf="parent"
-                app:layout_constraintEnd_toEndOf="parent"
-                app:layout_constraintTop_toBottomOf="@id/group_call_icon"
-                app:layout_constraintBottom_toTopOf="@id/contacts_and_suggestions_list"/>
-
             <androidx.recyclerview.widget.RecyclerView
                 android:id="@+id/contacts_and_suggestions_list"
                 android:layout_width="0dp"
@@ -211,7 +193,7 @@
                 android:visibility="@{viewModel.contactsAndSuggestionsList.size() == 0 ? View.GONE : View.VISIBLE}"
                 app:layout_constraintStart_toStartOf="parent"
                 app:layout_constraintEnd_toEndOf="parent"
-                app:layout_constraintTop_toBottomOf="@id/contacts_and_suggestions_label"
+                app:layout_constraintTop_toBottomOf="@id/group_call_icon"
                 app:layout_constraintBottom_toBottomOf="parent" />
 
         </androidx.constraintlayout.widget.ConstraintLayout>

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

@@ -1,9 +1,21 @@
 <?xml version="1.0" encoding="utf-8"?>
-<androidx.appcompat.widget.AppCompatTextView xmlns:android="http://schemas.android.com/apk/res/android"
-    style="@style/section_header_style"
-    android:layout_width="match_parent"
-    android:layout_height="wrap_content"
-    android:paddingStart="21dp"
-    android:paddingTop="16dp"
-    android:paddingBottom="16dp"
-    android:text="@string/call_start_suggestions_list_title"/>
+<layout
+    xmlns:android="http://schemas.android.com/apk/res/android">
+
+    <data>
+        <import type="android.view.View" />
+    </data>
+
+    <androidx.appcompat.widget.AppCompatTextView
+        style="@style/section_header_style"
+        android:id="@+id/header"
+        android:background="@color/white"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:paddingStart="21dp"
+        android:paddingTop="16dp"
+        android:paddingBottom="16dp"
+        android:text="@string/call_start_suggestions_list_title"
+        android:gravity="center_vertical"/>
+
+</layout>