fix: Order by clause cannot contain a field with an equality filter p…

…rice

Fixes issue "firebase/friendlyeats-android#118" by removing the "Sort by Price" option when user filters results by a particular Price. The "Sort by Price" option is added back when user does not filter by a particular Price, i.e., when user sets the "Price" spinner to "Any price" option.

app/src/main/java/com/google/firebase/example/fireeats/FilterDialogFragment.java

@@ -20,11 +20,15 @@
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
+import android.widget.AdapterView;
+import android.widget.ArrayAdapter;
 
 import com.google.firebase.example.fireeats.databinding.DialogFiltersBinding;
 import com.google.firebase.example.fireeats.model.Restaurant;
 import com.google.firebase.firestore.Query;
 
+import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Objects;
 
 import androidx.annotation.NonNull;
@@ -34,12 +38,21 @@
 /**
  * Dialog Fragment containing filter form.
  */
-public class FilterDialogFragment extends DialogFragment implements View.OnClickListener {
+public class FilterDialogFragment extends DialogFragment
+        implements View.OnClickListener, AdapterView.OnItemSelectedListener {
 
+    // Constant used for logs
     public static final String TAG = "FilterDialog";
+
+    // Constant for when "Price" filter is not selected, i.e., set to the default "Any Price"
+    private static final int ANY_PRICE = -1;
+
     private DialogFiltersBinding mBinding;
     private FilterListener mFilterListener;
 
+    // ArrayAdapter instance for "Sort" Spinner
+    private ArrayAdapter<String> mSortOptionsAdapter;
+
     @Nullable
     @Override
     public View onCreateView(@NonNull LayoutInflater inflater,
@@ -48,6 +61,25 @@ public View onCreateView(@NonNull LayoutInflater inflater,
         // Inflate with ViewBinding
         mBinding = DialogFiltersBinding.inflate(inflater, container, false);
 
+        // Set mutable data for "Sort" Spinner
+        ArrayList<String> sortByOptions = new ArrayList<>(
+                Arrays.asList(requireContext().getResources().getStringArray(R.array.sort_by))
+        );
+        // Create Adapter for "Sort" Spinner, with default layout for Spinner item
+        mSortOptionsAdapter = new ArrayAdapter<>(
+                requireContext(),
+                android.R.layout.simple_spinner_item,
+                sortByOptions
+        );
+        // Set layout to use when list of choices appear as dropdown
+        mSortOptionsAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
+        // Set Adapter for "Sort" Spinner
+        mBinding.spinnerSort.setAdapter(mSortOptionsAdapter);
+
+        // Add Item Click listener on "Price" Spinner
+        mBinding.spinnerPrice.setOnItemSelectedListener(this);
+
+        // Add Click listeners on Dialog Buttons
         mBinding.buttonSearch.setOnClickListener(this);
         mBinding.buttonCancel.setOnClickListener(this);
 
@@ -132,7 +164,7 @@ private int getSelectedPrice() {
         } else if (selected.equals(getString(R.string.price_3))) {
             return 3;
         } else {
-            return -1;
+            return ANY_PRICE;
         }
     }
 
@@ -191,6 +223,67 @@ public Filters getFilters() {
         return filters;
     }
 
+    /**
+     * <p>Callback method to be invoked when an item in this view has been
+     * selected. This callback is invoked only when the newly selected
+     * position is different from the previously selected position or if
+     * there was no selected item.</p>
+     * <p>
+     * Implementers can call getItemAtPosition(position) if they need to access the
+     * data associated with the selected item.
+     *
+     * @param parent   The AdapterView where the selection happened
+     * @param view     The view within the AdapterView that was clicked
+     * @param position The position of the view in the adapter
+     * @param id       The row id of the item that is selected
+     */
+    @Override
+    public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
+        // Based on the "Price" Spinner selection,
+        // show/hide the "Sort by Price" option in "Sort" Spinner
+        modifySortByOptions(getSelectedPrice() == ANY_PRICE);
+    }
+
+    /**
+     * Callback method to be invoked when the selection disappears from this
+     * view. The selection can disappear for instance when touch is activated
+     * or when the adapter becomes empty.
+     *
+     * @param parent The AdapterView that now contains no selected item.
+     */
+    @Override
+    public void onNothingSelected(AdapterView<?> parent) {
+        // no-op
+    }
+
+    /**
+     * Removes the "Sort by Price" option in "Sort" Spinner when a particular price
+     * is selected by the user through the "Price" Spinner.
+     * <p/>
+     * When a particular price is not selected, i.e., when "Price" Spinner is set to "Any price",
+     * then the "Sort by Price" option will be added back to the "Sort" Spinner if not present.
+     *
+     * @param showSortByPrice A {@link Boolean} to either add or remove the "Sort by Price" option
+     *                        in "Sort" Spinner. When {@code true}, the "Sort by Price" option will
+     *                        be added back if not present; otherwise it will be removed.
+     */
+    private void modifySortByOptions(boolean showSortByPrice) {
+        // Read the position of "Sort by Price" option in "Sort" Spinner
+        int sortByPricePosition = mSortOptionsAdapter.getPosition(getString(R.string.sort_by_price));
+
+        if (showSortByPrice) {
+            // Add the "Sort by Price" option if not present in the adapter
+            if (sortByPricePosition == -1) {
+                mSortOptionsAdapter.add(getString(R.string.sort_by_price));
+            }
+        } else {
+            // Remove the "Sort by Price" option from the adapter
+            if (sortByPricePosition > -1) {
+                mSortOptionsAdapter.remove(mSortOptionsAdapter.getItem(sortByPricePosition));
+            }
+        }
+    }
+
     interface FilterListener {
 
         void onFilter(Filters filters);

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

@@ -1,6 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
     android:id="@+id/filters_form"
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
@@ -98,7 +99,7 @@
             android:layout_centerVertical="true"
             android:layout_toEndOf="@+id/icon_sort"
             android:layout_toRightOf="@+id/icon_sort"
-            android:entries="@array/sort_by" />
+            tools:entries="@array/sort_by" />
     </RelativeLayout>
 
     <!-- Cancel and apply buttons -->