[Android] Fix a crash related to zeroed scanCode

shell/platform/android/io/flutter/embedding/android/KeyEmbedderResponder.java

@@ -122,7 +122,7 @@ void updatePressingState(@NonNull Long physicalKey, @Nullable Long logicalKey) {
   // the current event in consideration.
   //
   // Events that should be synthesized before the main event are synthesized
-  // immediately, while events that should be syntehsized after the main event are appended to
+  // immediately, while events that should be synthesized after the main event are appended to
   // `postSynchronize`.
   //
   // Although Android KeyEvent defined bitmasks for sided modifiers (SHIFT_LEFT_ON and
@@ -133,6 +133,7 @@ void synchronizePressingKey(
       PressingGoal goal,
       boolean truePressed,
       long eventLogicalKey,
+      long eventPhysicalKey,
       KeyEvent event,
       ArrayList<Runnable> postSynchronize) {
     // During an incoming event, there might be a synthesized Flutter event for each key of each
@@ -151,8 +152,8 @@ void synchronizePressingKey(
     // 2. Derive the pre-event state of the event key (if applicable.)
     for (int keyIdx = 0; keyIdx < goal.keys.length; keyIdx += 1) {
       final KeyboardMap.KeyPair key = goal.keys[keyIdx];
-      nowStates[keyIdx] = pressingRecords.containsKey(goal.keys[keyIdx].physicalKey);
-      if (goal.keys[keyIdx].logicalKey == eventLogicalKey) {
+      nowStates[keyIdx] = pressingRecords.containsKey(key.physicalKey);
+      if (key.logicalKey == eventLogicalKey) {
         switch (getEventType(event)) {
           case kDown:
             preEventStates[keyIdx] = false;
@@ -161,7 +162,7 @@ void synchronizePressingKey(
               postSynchronize.add(
                   () ->
                       synthesizeEvent(
-                          false, key.logicalKey, key.physicalKey, event.getEventTime()));
+                          false, key.logicalKey, eventPhysicalKey, event.getEventTime()));
             }
             break;
           case kUp:
@@ -273,7 +274,12 @@ private boolean handleEventImpl(
     final ArrayList<Runnable> postSynchronizeEvents = new ArrayList<>();
     for (final PressingGoal goal : KeyboardMap.pressingGoals) {
       synchronizePressingKey(
-          goal, (event.getMetaState() & goal.mask) != 0, logicalKey, event, postSynchronizeEvents);
+          goal,
+          (event.getMetaState() & goal.mask) != 0,
+          logicalKey,
+          physicalKey,
+          event,
+          postSynchronizeEvents);
     }
 
     for (final TogglingGoal goal : togglingGoals.values()) {

shell/platform/android/test/io/flutter/embedding/android/KeyboardManagerTest.java

@@ -1350,7 +1350,7 @@ public void synchronizeOtherModifiers() {
   @Test
   public void synchronizeModifiersForConflictingMetaState() {
     // Test if ShiftLeft can be correctly synchronized during down events of
-    // ShiftLeft that has 0 for its metaState.
+    // ShiftLeft that have 0 for their metaState.
     final KeyboardTester tester = new KeyboardTester();
     final ArrayList<CallRecord> calls = new ArrayList<>();
     // Even though the event is for ShiftRight, we still set SHIFT | SHIFT_LEFT here.
@@ -1396,6 +1396,31 @@ public void synchronizeModifiersForConflictingMetaState() {
     calls.clear();
   }
 
+  // Regression test for https://github.com/flutter/flutter/issues/110640
+  @Test
+  public void synchronizeModifiersForZeroedScanCode() {
+    // Test if ShiftLeft can be correctly synchronized during down events of
+    // ShiftLeft that have 0 for their metaState and 0 for their scanCode.
+    final KeyboardTester tester = new KeyboardTester();
+    final ArrayList<CallRecord> calls = new ArrayList<>();
+
+    tester.recordEmbedderCallsTo(calls);
+    tester.respondToTextInputWith(true); // Suppress redispatching
+
+    // Test: DOWN event when the current state is 0 and scanCode is 0.
+    final KeyEvent keyEvent = new FakeKeyEvent(ACTION_DOWN, 0, KEYCODE_SHIFT_LEFT, 0, '\0', 0);
+    // Compute physicalKey in the same way as KeyboardManager.getPhysicalKey.
+    final Long physicalKey = KEYCODE_SHIFT_LEFT | KeyboardMap.kAndroidPlane;
+
+    assertEquals(tester.keyboardManager.handleEvent(keyEvent), true);
+    assertEquals(calls.size(), 2);
+    assertEmbedderEventEquals(
+        calls.get(0).keyData, Type.kDown, physicalKey, LOGICAL_SHIFT_LEFT, null, false);
+    assertEmbedderEventEquals(
+        calls.get(1).keyData, Type.kUp, physicalKey, LOGICAL_SHIFT_LEFT, null, true);
+    calls.clear();
+  }
+
   @Test
   public void normalCapsLockEvents() {
     final KeyboardTester tester = new KeyboardTester();