Force translucent on iOS 12 when background is transparent

lib/ios/TopBarPresenter.m

@@ -72,6 +72,7 @@
     if (self.transparent) {
         [self setBackgroundColorTransparent];
     } else if (_backgroundColor) {
+        self.navigationController.navigationBar.translucent = NO;
         self.navigationController.navigationBar.barTintColor = _backgroundColor;
     } else if (_translucent) {
         self.navigationController.navigationBar.translucent = YES;
@@ -83,6 +84,7 @@
 
 - (void)setBackgroundColorTransparent {
     self.navigationController.navigationBar.barTintColor = UIColor.clearColor;
+    self.navigationController.navigationBar.translucent = YES;
     self.navigationController.navigationBar.shadowImage = [UIImage new];
     [self.navigationController.navigationBar setBackgroundImage:[UIImage new] forBarMetrics:UIBarMetricsDefault];
 }

playground/ios/NavigationIOS12Tests/RNNRootViewControllerTest.m

@@ -185,6 +185,7 @@
 	
 	nav.navigationBar.barTintColor = UIColor.clearColor;
 	XCTAssertTrue([nav.navigationBar.barTintColor isEqual:UIColor.clearColor]);
+	XCTAssertTrue(nav.navigationBar.isTranslucent);
 }
 
 -(void)testTopBarTransparent_BOOL_false {
@@ -192,7 +193,7 @@
 	__unused RNNStackController* nav = [self createNavigationController];
 	self.options.topBar.background.color = [[Color alloc] initWithValue:inputColor];
 	[self.uut viewWillAppear:false];
-
+	XCTAssertFalse(nav.navigationBar.isTranslucent);
 	XCTAssertFalse([nav.navigationBar.barTintColor isEqual:UIColor.clearColor]);
 }