Fix PickerAndroid will reset selected value during items update. (#24793

)

Summary:
Fixes #13351

Two root causes:
1. Android Spinner will reset selection to undefined after setAdapter()
   which will trigger onValueChange().
   The behavior is not expected for RN.
   And the solution is to setSelection() explicitly

2. In original implementation, it setups `items` immediately,
   but delays the `selected` setup after update transaction.
   There will be some race condition and incosistency
   if update `items` only.
   The fix will do the setup all after update transaction.

[Android] [Fixed] - Fix #13351 PickerAndroid will reset selected value during items update.
Pull Request resolved: #24793

Differential Revision: D15293516

Pulled By: cpojer

fbshipit-source-id: 5a99a60015c7e1b2968252cdc0b2661d52a15b9d

ReactAndroid/src/main/java/com/facebook/react/views/picker/ReactPicker.java

@@ -13,6 +13,7 @@
 import android.view.View;
 import android.widget.AdapterView;
 import android.widget.Spinner;
+import android.widget.SpinnerAdapter;
 
 import com.facebook.react.common.annotations.VisibleForTesting;
 
@@ -23,6 +24,7 @@ public class ReactPicker extends AppCompatSpinner {
   private int mMode = Spinner.MODE_DIALOG;
   private @Nullable Integer mPrimaryColor;
   private @Nullable OnSelectListener mOnSelectListener;
+  private @Nullable SpinnerAdapter mStagedAdapter;
   private @Nullable Integer mStagedSelection;
 
   private final OnItemSelectedListener mItemSelectedListener = new OnItemSelectedListener() {
@@ -111,33 +113,42 @@ public void setOnSelectListener(@Nullable OnSelectListener onSelectListener) {
     return mOnSelectListener;
   }
 
+  /* package */ void setStagedAdapter(final SpinnerAdapter adapter) {
+   mStagedAdapter = adapter;
+  }
+
   /**
-   * Will cache "selection" value locally and set it only once {@link #updateStagedSelection} is
+   * Will cache "selection" value locally and set it only once {@link #commitStagedData} is
    * called
    */
-  public void setStagedSelection(int selection) {
+  /* package */ void setStagedSelection(int selection) {
     mStagedSelection = selection;
   }
 
-  public void updateStagedSelection() {
-    if (mStagedSelection != null) {
-      setSelectionWithSuppressEvent(mStagedSelection);
-      mStagedSelection = null;
-    }
-  }
-
   /**
-   * Set the selection while suppressing the follow-up {@link OnSelectListener#onItemSelected(int)}
-   * event. This is used so we don't get an event when changing the selection ourselves.
-   *
-   * @param position the position of the selected item
+   * Used to commit staged data into ReactPicker view.
+   * During this period, we will disable {@link OnSelectListener#onItemSelected(int)} temporarily,
+   * so we don't get an event when changing the items/selection ourselves.
    */
-  private void setSelectionWithSuppressEvent(int position) {
-    if (position != getSelectedItemPosition()) {
-      setOnItemSelectedListener(null);
-      setSelection(position, false);
-      setOnItemSelectedListener(mItemSelectedListener);
+  /* package */ void commitStagedData() {
+    setOnItemSelectedListener(null);
+
+    final int origSelection = getSelectedItemPosition();
+    if (mStagedAdapter != null && mStagedAdapter != getAdapter()) {
+      setAdapter(mStagedAdapter);
+      // After setAdapter(), Spinner will reset selection and cause unnecessary onValueChange event.
+      // Explicitly setup selection again to prevent this.
+      // Ref: https://android.googlesource.com/platform/frameworks/base/+/master/core/java/android/widget/AbsSpinner.java#123
+      setSelection(origSelection, false);
+      mStagedAdapter = null;
     }
+
+    if (mStagedSelection != null && mStagedSelection != origSelection) {
+      setSelection(mStagedSelection, false);
+      mStagedSelection = null;
+    }
+
+    setOnItemSelectedListener(mItemSelectedListener);
   }
 
   public @Nullable Integer getPrimaryColor() {

ReactAndroid/src/main/java/com/facebook/react/views/picker/ReactPickerManager.java

@@ -44,9 +44,9 @@ public void setItems(ReactPicker view, @Nullable ReadableArray items) {
       }
       ReactPickerAdapter adapter = new ReactPickerAdapter(view.getContext(), data);
       adapter.setPrimaryTextColor(view.getPrimaryColor());
-      view.setAdapter(adapter);
+      view.setStagedAdapter(adapter);
     } else {
-      view.setAdapter(null);
+      view.setStagedAdapter(null);
     }
   }
 
@@ -77,7 +77,7 @@ public void setSelected(ReactPicker view, int selected) {
   @Override
   protected void onAfterUpdateTransaction(ReactPicker view) {
     super.onAfterUpdateTransaction(view);
-    view.updateStagedSelection();
+    view.commitStagedData();
   }
 
   @Override