smartlist: prevent appbar to collapse when no conversation

GitLab: #1547

Change-Id: Ie7662171250ba5b0f54215351e1f2684e1e53454

jami-android/app/src/main/java/cx/ring/fragments/HomeFragment.kt

@@ -46,6 +46,7 @@ import androidx.transition.Fade
 import androidx.transition.Slide
 import androidx.transition.TransitionManager
 import com.google.android.material.appbar.AppBarLayout
+import com.google.android.material.appbar.AppBarLayout.Behavior.DragCallback
 import com.google.android.material.dialog.MaterialAlertDialogBuilder
 import cx.ring.R
 import cx.ring.account.AccountWizardActivity
@@ -362,7 +363,8 @@ class HomeFragment: BaseSupportFragment<HomePresenter, HomeView>(),
             (binding.invitationCard.invitationGroup.layoutParams as ViewGroup.MarginLayoutParams)
                 .setMargins(it, it, it, 2*it)
         }
-        // Enable to possibility to scroll the invitation pending list.
+
+        // Enable invitation pending list scroll (remove side effect with appbar behavior).
         (binding.appBar.layoutParams as CoordinatorLayout.LayoutParams).behavior = null
 
         // Hide everything unneeded.
@@ -411,9 +413,8 @@ class HomeFragment: BaseSupportFragment<HomePresenter, HomeView>(),
             (binding.invitationCard.invitationGroup.layoutParams as ViewGroup.MarginLayoutParams)
                 .setMargins(it, 0, it, 0)
         }
-        // Disable possibility to scroll the invitation pending list.
-        (binding.appBar.layoutParams as CoordinatorLayout.LayoutParams).behavior =
-            AppBarLayout.Behavior()
+
+        disableAppBarScroll()
 
         // Show everything needed.
         binding.donationCard.donationCard.isVisible = presenter.donationCardIsVisible
@@ -447,6 +448,8 @@ class HomeFragment: BaseSupportFragment<HomePresenter, HomeView>(),
         super.onViewCreated(view, savedInstanceState)
         pagerContent = mBinding!!.fragmentContainer.getFragment()
 
+        disableAppBarScroll()
+
         // Subscribe on fragmentContainer to add scroll listener on the recycler view.
         mBinding!!.fragmentContainer.getFragment<SmartListFragment>().viewLifecycleOwnerLiveData
             .observe(viewLifecycleOwner) {
@@ -619,6 +622,16 @@ class HomeFragment: BaseSupportFragment<HomePresenter, HomeView>(),
         b.searchView.hide()
     }
 
+    /** Prevent appbar to be collapsed by direct scroll. */
+    private fun disableAppBarScroll() {
+        (mBinding!!.appBar.layoutParams as CoordinatorLayout.LayoutParams).behavior =
+            AppBarLayout.Behavior().apply {
+                setDragCallback(object : DragCallback() {
+                    override fun canDrag(appBarLayout: AppBarLayout): Boolean = false
+                })
+            }
+    }
+
     companion object {
         private val TAG = HomeFragment::class.simpleName!!
         const val TAB_CONVERSATIONS = 0