collapse start chat button

src/main/java/eu/siacs/conversations/ui/ConversationsOverviewFragment.java

@@ -299,6 +299,7 @@ public class ConversationsOverviewFragment extends XmppFragment {
 		});
 		this.binding.list.setAdapter(this.conversationsAdapter);
 		this.binding.list.setLayoutManager(new LinearLayoutManager(getActivity(),LinearLayoutManager.VERTICAL,false));
+		this.binding.list.addOnScrollListener(ExtendedFabSizeChanger.of(binding.fab));
 		this.touchHelper = new ItemTouchHelper(this.callback);
 		this.touchHelper.attachToRecyclerView(this.binding.list);
 		return binding.getRoot();

src/main/java/eu/siacs/conversations/ui/ExtendedFabSizeChanger.java

@@ -0,0 +1,29 @@
+package eu.siacs.conversations.ui;
+
+import androidx.annotation.NonNull;
+import androidx.recyclerview.widget.RecyclerView;
+import com.google.android.material.floatingactionbutton.ExtendedFloatingActionButton;
+
+public class ExtendedFabSizeChanger extends RecyclerView.OnScrollListener {
+
+    private final ExtendedFloatingActionButton extendedFloatingActionButton;
+
+    private ExtendedFabSizeChanger(
+            final ExtendedFloatingActionButton extendedFloatingActionButton) {
+        this.extendedFloatingActionButton = extendedFloatingActionButton;
+    }
+
+    @Override
+    public void onScrolled(@NonNull RecyclerView recyclerView, int dx, int dy) {
+        super.onScrolled(recyclerView, dx, dy);
+        if (RecyclerViews.findFirstVisibleItemPosition(recyclerView) > 0) {
+            extendedFloatingActionButton.shrink();
+        } else {
+            extendedFloatingActionButton.extend();
+        }
+    }
+
+    public static RecyclerView.OnScrollListener of(final ExtendedFloatingActionButton fab) {
+        return new ExtendedFabSizeChanger(fab);
+    }
+}

src/main/java/eu/siacs/conversations/ui/RecyclerViews.java

@@ -0,0 +1,29 @@
+package eu.siacs.conversations.ui;
+
+import androidx.recyclerview.widget.LinearLayoutManager;
+import androidx.recyclerview.widget.RecyclerView;
+
+public final class RecyclerViews {
+
+    private RecyclerViews() {
+        throw new IllegalStateException("Do not instantiate me");
+    }
+
+    public static boolean scrolledToTop(final RecyclerView recyclerView) {
+        final RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();
+        if (layoutManager instanceof LinearLayoutManager linearLayoutManager) {
+            return linearLayoutManager.findFirstCompletelyVisibleItemPosition() == 0;
+        } else {
+            return false;
+        }
+    }
+
+    public static int findFirstVisibleItemPosition(final RecyclerView recyclerView) {
+        final RecyclerView.LayoutManager layoutManager = recyclerView.getLayoutManager();
+        if (layoutManager instanceof LinearLayoutManager linearLayoutManager) {
+            return linearLayoutManager.findFirstVisibleItemPosition();
+        } else {
+            return RecyclerView.NO_POSITION;
+        }
+    }
+}