Rearrange observers for DirectItemsAdapter so that it is never initialised without a thread

app/src/main/java/awais/instagrabber/adapters/DirectItemsAdapter.java

@@ -58,6 +58,7 @@ public final class DirectItemsAdapter extends RecyclerView.Adapter<RecyclerView.
     private final ProfileModel currentUser;
     private DirectThread thread;
     private final AsyncListDiffer<DirectItemOrHeader> differ;
+    private List<DirectItem> items;
 
     private static final DiffUtil.ItemCallback<DirectItemOrHeader> diffCallback = new DiffUtil.ItemCallback<DirectItemOrHeader>() {
         @Override
@@ -97,8 +98,10 @@ public final class DirectItemsAdapter extends RecyclerView.Adapter<RecyclerView.
         }
     };
 
-    public DirectItemsAdapter(@NonNull final ProfileModel currentUser) {
+    public DirectItemsAdapter(@NonNull final ProfileModel currentUser,
+                              @NonNull final DirectThread thread) {
         this.currentUser = currentUser;
+        this.thread = thread;
         differ = new AsyncListDiffer<>(new AdapterListUpdateCallback(this),
                                        new AsyncDifferConfig.Builder<>(diffCallback).build());
         // this.onClickListener = onClickListener;
@@ -118,9 +121,10 @@ public final class DirectItemsAdapter extends RecyclerView.Adapter<RecyclerView.
         return getItemViewHolder(layoutInflater, baseBinding, directItemType);
     }
 
+    @NonNull
     private DirectItemViewHolder getItemViewHolder(final LayoutInflater layoutInflater,
                                                    final LayoutDmBaseBinding baseBinding,
-                                                   final DirectItemType directItemType) {
+                                                   @NonNull final DirectItemType directItemType) {
         switch (directItemType) {
             case TEXT: {
                 final LayoutDmTextBinding binding = LayoutDmTextBinding.inflate(layoutInflater, baseBinding.message, false);
@@ -232,6 +236,7 @@ public final class DirectItemsAdapter extends RecyclerView.Adapter<RecyclerView.
     public void setThread(final DirectThread thread) {
         if (thread == null) return;
         this.thread = thread;
+        notifyDataSetChanged();
     }
 
     public void submitList(@Nullable final List<DirectItem> list) {
@@ -240,6 +245,7 @@ public final class DirectItemsAdapter extends RecyclerView.Adapter<RecyclerView.
             return;
         }
         differ.submitList(sectionAndSort(list));
+        this.items = list;
     }
 
     public void submitList(@Nullable final List<DirectItem> list, @Nullable final Runnable commitCallback) {
@@ -248,6 +254,7 @@ public final class DirectItemsAdapter extends RecyclerView.Adapter<RecyclerView.
             return;
         }
         differ.submitList(sectionAndSort(list), commitCallback);
+        this.items = list;
     }
 
     private List<DirectItemOrHeader> sectionAndSort(final List<DirectItem> list) {
@@ -289,6 +296,10 @@ public final class DirectItemsAdapter extends RecyclerView.Adapter<RecyclerView.
         return differ.getCurrentList();
     }
 
+    public List<DirectItem> getItems() {
+        return items;
+    }
+
     @Override
     public void onViewRecycled(@NonNull final RecyclerView.ViewHolder holder) {
         if (holder instanceof DirectItemViewHolder) {
@@ -303,6 +314,10 @@ public final class DirectItemsAdapter extends RecyclerView.Adapter<RecyclerView.
         }
     }
 
+    public DirectThread getThread() {
+        return thread;
+    }
+
     public static class DirectItemOrHeader {
         Date date;
         DirectItem item;

app/src/main/java/awais/instagrabber/adapters/viewholder/directmessages/DirectItemViewHolder.java

@@ -49,7 +49,7 @@ public abstract class DirectItemViewHolder extends RecyclerView.ViewHolder {
 
     public DirectItemViewHolder(@NonNull final LayoutDmBaseBinding binding,
                                 @NonNull final ProfileModel currentUser,
-                                final DirectThread thread,
+                                @NonNull final DirectThread thread,
                                 @NonNull final View.OnClickListener onClickListener) {
         super(binding.getRoot());
         this.binding = binding;

app/src/main/java/awais/instagrabber/fragments/directmessages/DirectMessageThreadFragment.java

@@ -14,6 +14,7 @@ import android.net.Uri;
 import android.os.Bundle;
 import android.text.Editable;
 import android.util.Log;
+import android.util.Pair;
 import android.view.KeyEvent;
 import android.view.LayoutInflater;
 import android.view.Menu;
@@ -30,6 +31,8 @@ import androidx.appcompat.app.ActionBar;
 import androidx.constraintlayout.widget.ConstraintLayout;
 import androidx.core.content.ContextCompat;
 import androidx.fragment.app.Fragment;
+import androidx.lifecycle.LiveData;
+import androidx.lifecycle.MediatorLiveData;
 import androidx.lifecycle.MutableLiveData;
 import androidx.lifecycle.ViewModelProvider;
 import androidx.lifecycle.ViewModelStoreOwner;
@@ -313,10 +316,8 @@ public class DirectMessageThreadFragment extends Fragment {
         super.onResume();
         fragmentActivity.getWindow().setSoftInputMode(SOFT_INPUT_ADJUST_NOTHING | SOFT_INPUT_STATE_HIDDEN);
         if (wasKbShowing) {
-            appExecutors.mainThread().execute(() -> {
             binding.input.requestFocus();
             binding.input.post(this::showKeyboard);
-            });
             wasKbShowing = false;
         }
         setObservers();
@@ -332,12 +333,6 @@ public class DirectMessageThreadFragment extends Fragment {
         cleanup();
     }
 
-    @Override
-    public void onDestroy() {
-        super.onDestroy();
-        cleanup();
-    }
-
     private void cleanup() {
         if (prevTitleRunnable != null) {
             appExecutors.mainThread().cancel(prevTitleRunnable);
@@ -363,13 +358,14 @@ public class DirectMessageThreadFragment extends Fragment {
         if (context == null) return;
         if (getArguments() == null) return;
         actionBar = fragmentActivity.getSupportActionBar();
-        setObservers();
         final DirectMessageThreadFragmentArgs fragmentArgs = DirectMessageThreadFragmentArgs.fromBundle(getArguments());
         viewModel.getThreadTitle().postValue(fragmentArgs.getTitle());
         final String threadId = fragmentArgs.getThreadId();
         viewModel.setThreadId(threadId);
         setupList();
         root.post(this::setupInput);
+        root.post(this::getInitialData);
+        setObservers();
     }
 
     private void getInitialData() {
@@ -386,9 +382,6 @@ public class DirectMessageThreadFragment extends Fragment {
             // setTitle(UPDATING_TITLE);
             final DirectThread thread = first.get();
             viewModel.setThread(thread);
-            if (itemsAdapter != null) {
-                itemsAdapter.setThread(thread);
-            }
             return;
         }
         viewModel.fetchChats();
@@ -554,15 +547,29 @@ public class DirectMessageThreadFragment extends Fragment {
             }
             setTitle(viewModel.getThreadTitle().getValue());
         });
-        viewModel.getThread().observe(getViewLifecycleOwner(), thread -> {
-            if (thread != null && itemsAdapter != null) itemsAdapter.setThread(thread);
+        final ItemsAdapterDataMerger itemsAdapterDataMerger = new ItemsAdapterDataMerger(appStateViewModel.getCurrentUser(), viewModel.getThread());
+        itemsAdapterDataMerger.observe(getViewLifecycleOwner(), userThreadPair -> {
+            viewModel.setCurrentUser(userThreadPair.first);
+            setupItemsAdapter(userThreadPair.first, userThreadPair.second);
         });
-        appStateViewModel.getCurrentUser().observe(getViewLifecycleOwner(), currentUser -> {
-            viewModel.setCurrentUser(currentUser);
-            setupItemsAdapter(currentUser);
-            viewModel.getItems().observe(
-                    getViewLifecycleOwner(),
-                    list -> itemsAdapter.submitList(list, () -> {
+        viewModel.getItems().observe(getViewLifecycleOwner(), this::submitItemsToAdapter);
+        final NavController navController = NavHostFragment.findNavController(this);
+        final NavBackStackEntry backStackEntry = navController.getCurrentBackStackEntry();
+        if (backStackEntry != null) {
+            final MutableLiveData<Object> resultLiveData = backStackEntry.getSavedStateHandle().getLiveData("result");
+            resultLiveData.observe(getViewLifecycleOwner(), result -> {
+                if (!(result instanceof Uri)) return;
+                final Uri uri = (Uri) result;
+                viewModel.sendUri(uri);
+                // clear result
+                resultLiveData.postValue(null);
+            });
+        }
+    }
+
+    private void submitItemsToAdapter(final List<DirectItem> items) {
+        if (itemsAdapter == null) return;
+        itemsAdapter.submitList(items, () -> {
             itemOrHeaders = itemsAdapter.getList();
             binding.chats.post(() -> {
                 final RecyclerView.LayoutManager layoutManager = binding.chats.getLayoutManager();
@@ -574,26 +581,27 @@ public class DirectMessageThreadFragment extends Fragment {
                     }
                 }
             });
-                    })
-            );
-        });
-        final NavController navController = NavHostFragment.findNavController(this);
-        final NavBackStackEntry backStackEntry = navController.getCurrentBackStackEntry();
-        if (backStackEntry != null) {
-            final MutableLiveData<Object> resultLiveData = backStackEntry.getSavedStateHandle().getLiveData("result");
-            resultLiveData.observe(getViewLifecycleOwner(), result -> {
-                if (!(result instanceof Uri)) return;
-                final Uri uri = (Uri) result;
-                viewModel.sendUri(uri);
         });
     }
-    }
 
-    private void setupItemsAdapter(final ProfileModel currentUser) {
-        if (itemsAdapter != null) return;
-        itemsAdapter = new DirectItemsAdapter(currentUser);
+    private void setupItemsAdapter(final ProfileModel currentUser, final DirectThread thread) {
+        if (itemsAdapter != null) {
+            if (itemsAdapter.getThread() == thread) return;
+            itemsAdapter.setThread(thread);
+            return;
+        }
+        itemsAdapter = new DirectItemsAdapter(currentUser, thread);
         itemsAdapter.setHasStableIds(true);
+        itemsAdapter.setStateRestorationPolicy(RecyclerView.Adapter.StateRestorationPolicy.PREVENT_WHEN_EMPTY);
         binding.chats.setAdapter(itemsAdapter);
+        registerDataObserver();
+        final List<DirectItem> items = viewModel.getItems().getValue();
+        if (items != null && itemsAdapter.getItems() != items) {
+            submitItemsToAdapter(items);
+        }
+    }
+
+    private void registerDataObserver() {
         itemsAdapter.registerAdapterDataObserver(new RecyclerView.AdapterDataObserver() {
 
             @Override
@@ -607,7 +615,6 @@ public class DirectMessageThreadFragment extends Fragment {
                 }
             }
         });
-        root.post(this::getInitialData);
     }
 
     private void setupInput() {
@@ -1097,4 +1104,26 @@ public class DirectMessageThreadFragment extends Fragment {
         });
         animatorSet.start();
     }
+
+    public static class ItemsAdapterDataMerger extends MediatorLiveData<Pair<ProfileModel, DirectThread>> {
+        private ProfileModel user;
+        private DirectThread thread;
+
+        public ItemsAdapterDataMerger(final LiveData<ProfileModel> userLiveData,
+                                      final LiveData<DirectThread> threadLiveData) {
+            addSource(userLiveData, user -> {
+                this.user = user;
+                combine();
+            });
+            addSource(threadLiveData, thread -> {
+                this.thread = thread;
+                combine();
+            });
+        }
+
+        private void combine() {
+            if (user == null || thread == null) return;
+            setValue(new Pair<>(user, thread));
+        }
+    }
 }