NativeScript/packages/core/ui/bottom-navigation/index.ios.ts

// Types
import { TabContentItem } from '../tab-navigation-base/tab-content-item';
import { TabStrip } from '../tab-navigation-base/tab-strip';
import { TabStripItem } from '../tab-navigation-base/tab-strip-item';
import { getTransformedText } from '../text-base';
import { Enums } from '../enums';
// Requires
import { Color } from '../../color';
import { ImageSource } from '../../image-source';
import { Device } from '../../platform';
import { iOSNativeHelper, isFontIconURI, layout } from '../../utils';
import { CSSType, IOSHelper, View } from '../core/view';
import { Frame } from '../frame';
import { Font } from '../styling/font';
import { getIconSpecSize, itemsProperty, selectedIndexProperty, TabNavigationBase, tabStripProperty } from '../tab-navigation-base/tab-navigation-base';

// TODO:
// import { profile } from "../../profiling";

const maxTabsCount = 5;
const majorVersion = iOSNativeHelper.MajorVersion;
const isPhone = Device.deviceType === 'Phone';

@NativeClass
class UITabBarControllerImpl extends UITabBarController {
	private _owner: WeakRef<BottomNavigation>;

	public static initWithOwner(owner: WeakRef<BottomNavigation>): UITabBarControllerImpl {
		const handler = <UITabBarControllerImpl>UITabBarControllerImpl.new();
		handler._owner = owner;

		return handler;
	}

	// TODO
	// @profile
	public viewWillAppear(animated: boolean): void {
		super.viewWillAppear(animated);
		const owner = this._owner.get();
		if (!owner) {
			return;
		}

		// Unify translucent and opaque bars layout
		this.extendedLayoutIncludesOpaqueBars = true;

		IOSHelper.updateAutoAdjustScrollInsets(this, owner);

		if (!owner.parent) {
			owner.callLoaded();
		}
	}

	// TODO
	// @profile
	public viewDidDisappear(animated: boolean): void {
		super.viewDidDisappear(animated);
		const owner = this._owner.get();
		if (owner && !owner.parent && owner.isLoaded && !this.presentedViewController) {
			owner.callUnloaded();
		}
	}

	public viewWillTransitionToSizeWithTransitionCoordinator(size: CGSize, coordinator: UIViewControllerTransitionCoordinator): void {
		super.viewWillTransitionToSizeWithTransitionCoordinator(size, coordinator);
		coordinator.animateAlongsideTransitionCompletion(() => {
			const owner = this._owner.get();
			if (owner && owner.tabStrip && owner.tabStrip.items) {
				const tabStrip = owner.tabStrip;
				tabStrip.items.forEach((tabStripItem) => {
					updateBackgroundPositions(tabStrip, tabStripItem);

					const index = tabStripItem._index;
					const tabBarItemController = this.viewControllers[index];
					updateTitleAndIconPositions(tabStripItem, tabBarItemController.tabBarItem, tabBarItemController);
				});
			}
		}, null);
	}

	// Mind implementation for other controllers
	public traitCollectionDidChange(previousTraitCollection: UITraitCollection): void {
		super.traitCollectionDidChange(previousTraitCollection);

		if (majorVersion >= 13) {
			const owner = this._owner.get();
			if (owner && this.traitCollection.hasDifferentColorAppearanceComparedToTraitCollection && this.traitCollection.hasDifferentColorAppearanceComparedToTraitCollection(previousTraitCollection)) {
				owner.notify({
					eventName: IOSHelper.traitCollectionColorAppearanceChangedEvent,
					object: owner,
				});
			}
		}
	}
}

@NativeClass
class UITabBarControllerDelegateImpl extends NSObject implements UITabBarControllerDelegate {
	public static ObjCProtocols = [UITabBarControllerDelegate];

	private _owner: WeakRef<BottomNavigation>;

	public static initWithOwner(owner: WeakRef<BottomNavigation>): UITabBarControllerDelegateImpl {
		const delegate = <UITabBarControllerDelegateImpl>UITabBarControllerDelegateImpl.new();
		delegate._owner = owner;

		return delegate;
	}

	public tabBarControllerShouldSelectViewController(tabBarController: UITabBarController, viewController: UIViewController): boolean {
		// TODO
		// if (Trace.isEnabled()) {
		//     Trace.write("TabView.delegate.SHOULD_select(" + tabBarController + ", " + viewController + ");", Trace.categories.Debug);
		// }

		const owner = this._owner.get();
		if (owner) {
			// "< More" cannot be visible after clicking on the main tab bar buttons.
			const backToMoreWillBeVisible = false;
			owner._handleTwoNavigationBars(backToMoreWillBeVisible);

			if (tabBarController.viewControllers) {
				const position = tabBarController.viewControllers.indexOfObject(viewController);
				if (position !== NSNotFound) {
					const tabStrip = owner.tabStrip;
					const tabStripItems = tabStrip && tabStrip.items;

					if (tabStripItems && tabStripItems[position]) {
						tabStripItems[position]._emit(TabStripItem.tapEvent);
						tabStrip.notify({
							eventName: TabStrip.itemTapEvent,
							object: tabStrip,
							index: position,
						});
					}
				}
			}
		}

		if ((<any>tabBarController).selectedViewController === viewController) {
			return false;
		}

		(<any>tabBarController)._willSelectViewController = viewController;

		return true;
	}

	public tabBarControllerDidSelectViewController(tabBarController: UITabBarController, viewController: UIViewController): void {
		// TODO
		// if (Trace.isEnabled()) {
		//     Trace.write("TabView.delegate.DID_select(" + tabBarController + ", " + viewController + ");", Trace.categories.Debug);
		// }

		const owner = this._owner.get();
		if (owner) {
			owner._onViewControllerShown(viewController);
		}

		(<any>tabBarController)._willSelectViewController = undefined;
	}
}

@NativeClass
class UINavigationControllerDelegateImpl extends NSObject implements UINavigationControllerDelegate {
	public static ObjCProtocols = [UINavigationControllerDelegate];

	private _owner: WeakRef<BottomNavigation>;

	public static initWithOwner(owner: WeakRef<BottomNavigation>): UINavigationControllerDelegateImpl {
		const delegate = <UINavigationControllerDelegateImpl>UINavigationControllerDelegateImpl.new();
		delegate._owner = owner;

		return delegate;
	}

	navigationControllerWillShowViewControllerAnimated(navigationController: UINavigationController, viewController: UIViewController, animated: boolean): void {
		// TODO
		// if (Trace.isEnabled()) {
		//     Trace.write("TabView.moreNavigationController.WILL_show(" + navigationController + ", " + viewController + ", " + animated + ");", Trace.categories.Debug);
		// }

		const owner = this._owner.get();
		if (owner) {
			// If viewController is one of our tab item controllers, then "< More" will be visible shortly.
			// Otherwise viewController is the UIMoreListController which shows the list of all tabs beyond the 4th tab.
			const backToMoreWillBeVisible = owner._ios.viewControllers.containsObject(viewController);
			owner._handleTwoNavigationBars(backToMoreWillBeVisible);
		}
	}

	navigationControllerDidShowViewControllerAnimated(navigationController: UINavigationController, viewController: UIViewController, animated: boolean): void {
		// TODO
		// if (Trace.isEnabled()) {
		//     Trace.write("TabView.moreNavigationController.DID_show(" + navigationController + ", " + viewController + ", " + animated + ");", Trace.categories.Debug);
		// }
		// We don't need Edit button in More screen.
		navigationController.navigationBar.topItem.rightBarButtonItem = null;
		const owner = this._owner.get();
		if (owner) {
			owner._onViewControllerShown(viewController);
		}
	}
}

function updateBackgroundPositions(tabStrip: TabStrip, tabStripItem: TabStripItem) {
	let bgView = (<any>tabStripItem).bgView;
	const index = tabStripItem._index;
	const width = tabStrip.nativeView.frame.size.width / tabStrip.items.length;
	const frame = CGRectMake(width * index, 0, width, tabStrip.nativeView.frame.size.width);
	if (!bgView) {
		bgView = UIView.alloc().initWithFrame(frame);
		tabStrip.nativeView.insertSubviewAtIndex(bgView, 0);
		(<any>tabStripItem).bgView = bgView;
	} else {
		bgView.frame = frame;
	}

	const backgroundColor = tabStripItem.style.backgroundColor;
	bgView.backgroundColor = backgroundColor instanceof Color ? backgroundColor.ios : backgroundColor;
}

function updateTitleAndIconPositions(tabStripItem: TabStripItem, tabBarItem: UITabBarItem, controller: UIViewController) {
	if (!tabStripItem || !tabBarItem) {
		return;
	}

	// For iOS <11 icon is *always* above the text.
	// For iOS 11 icon is above the text *only* on phones in portrait mode.
	const orientation = controller.interfaceOrientation;
	const isPortrait = orientation !== UIInterfaceOrientation.LandscapeLeft && orientation !== UIInterfaceOrientation.LandscapeRight;
	const isIconAboveTitle = majorVersion < 11 || (isPhone && isPortrait);

	if (!tabStripItem.iconSource) {
		if (isIconAboveTitle) {
			tabBarItem.titlePositionAdjustment = {
				horizontal: 0,
				vertical: -20,
			};
		} else {
			tabBarItem.titlePositionAdjustment = { horizontal: 0, vertical: 0 };
		}
	}

	if (!tabStripItem.title) {
		if (isIconAboveTitle) {
			tabBarItem.imageInsets = new UIEdgeInsets({
				top: 6,
				left: 0,
				bottom: -6,
				right: 0,
			});
		} else {
			tabBarItem.imageInsets = new UIEdgeInsets({
				top: 0,
				left: 0,
				bottom: 0,
				right: 0,
			});
		}
	}
}

@CSSType('BottomNavigation')
export class BottomNavigation extends TabNavigationBase {
	public viewController: UITabBarControllerImpl;
	public items: TabContentItem[];
	public _ios: UITabBarControllerImpl;
	private _delegate: UITabBarControllerDelegateImpl;
	private _moreNavigationControllerDelegate: UINavigationControllerDelegateImpl;
	private _iconsCache = {};
	private _selectedItemColor: Color;
	private _unSelectedItemColor: Color;

	constructor() {
		super();

		this.viewController = this._ios = UITabBarControllerImpl.initWithOwner(new WeakRef(this));
		this.nativeViewProtected = this._ios.view;
	}

	initNativeView() {
		super.initNativeView();
		this._delegate = UITabBarControllerDelegateImpl.initWithOwner(new WeakRef(this));
		this._moreNavigationControllerDelegate = UINavigationControllerDelegateImpl.initWithOwner(new WeakRef(this));
		if (!this.tabStrip) {
			this.viewController.tabBar.hidden = true;
		}
	}

	disposeNativeView() {
		this._delegate = null;
		this._moreNavigationControllerDelegate = null;
		super.disposeNativeView();
	}

	// TODO
	// @profile
	public onLoaded() {
		super.onLoaded();

		this.setViewControllers(this.items);

		const selectedIndex = this.selectedIndex;
		const selectedView = this.items && this.items[selectedIndex] && this.items[selectedIndex].content;
		if (selectedView instanceof Frame) {
			selectedView._pushInFrameStackRecursive();
		}

		this._ios.delegate = this._delegate;
	}

	public onUnloaded() {
		this._ios.delegate = null;
		this._ios.moreNavigationController.delegate = null;
		super.onUnloaded();
	}

	// @ts-ignore
	get ios(): UITabBarController {
		return this._ios;
	}

	public layoutNativeView(left: number, top: number, right: number, bottom: number): void {
		//
	}

	public _setNativeViewFrame(nativeView: UIView, frame: CGRect) {
		//
	}

	public onSelectedIndexChanged(oldIndex: number, newIndex: number): void {
		const items = this.items;
		if (!items) {
			return;
		}

		const oldItem = items[oldIndex];
		if (oldItem) {
			oldItem.canBeLoaded = false;
			oldItem.unloadView(oldItem.content);
		}

		const newItem = items[newIndex];
		if (newItem && this.isLoaded) {
			const selectedView = items[newIndex].content;
			if (selectedView instanceof Frame) {
				selectedView._pushInFrameStackRecursive();
			}

			newItem.canBeLoaded = true;
			newItem.loadView(newItem.content);
		}

		const tabStripItems = this.tabStrip && this.tabStrip.items;
		if (tabStripItems) {
			if (tabStripItems[newIndex]) {
				tabStripItems[newIndex]._emit(TabStripItem.selectEvent);
			}

			if (tabStripItems[oldIndex]) {
				tabStripItems[oldIndex]._emit(TabStripItem.unselectEvent);
			}
		}

		super.onSelectedIndexChanged(oldIndex, newIndex);
	}

	public getTabBarBackgroundColor(): UIColor {
		return this._ios.tabBar.barTintColor;
	}

	public setTabBarBackgroundColor(value: UIColor | Color): void {
		this._ios.tabBar.barTintColor = value instanceof Color ? value.ios : value;
		this.updateAllItemsColors();
	}

	public setTabBarItemTitle(tabStripItem: TabStripItem, value: string): void {
		tabStripItem.nativeView.title = value;
	}

	public setTabBarItemBackgroundColor(tabStripItem: TabStripItem, value: UIColor | Color): void {
		if (!this.tabStrip || !tabStripItem) {
			return;
		}

		updateBackgroundPositions(this.tabStrip, tabStripItem);
	}

	public setTabBarItemColor(tabStripItem: TabStripItem, value: UIColor | Color): void {
		this.setViewAttributes(tabStripItem.nativeView, tabStripItem.label);
	}

	private setItemColors(): void {
		if (this._selectedItemColor) {
			this.viewController.tabBar.selectedImageTintColor = this._selectedItemColor.ios;
		}
		if (this._unSelectedItemColor) {
			this.viewController.tabBar.unselectedItemTintColor = this._unSelectedItemColor.ios;
		}
	}

	private setIconColor(tabStripItem: TabStripItem, forceReload = false): void {
		if (forceReload || (!this._unSelectedItemColor && !this._selectedItemColor)) {
			// if selectedItemColor or unSelectedItemColor is set we don't respect the color from the style
			const tabStripColor = this.selectedIndex === tabStripItem._index ? this._selectedItemColor : this._unSelectedItemColor;

			const image = this.getIcon(tabStripItem, tabStripColor);

			tabStripItem.nativeView.image = image;
			tabStripItem.nativeView.selectedImage = image;
		}
	}

	public setTabBarIconColor(tabStripItem: TabStripItem, value: UIColor | Color): void {
		this.setIconColor(tabStripItem);
	}

	public setTabBarIconSource(tabStripItem: TabStripItem, value: UIColor | Color): void {
		this.updateItemColors(tabStripItem);
	}

	public setTabBarItemFontInternal(tabStripItem: TabStripItem, value: Font): void {
		this.setViewAttributes(tabStripItem.nativeView, tabStripItem.label);
	}

	public setTabBarItemTextTransform(tabStripItem: TabStripItem, value: Enums.TextTransformType): void {
		tabStripItem.nativeView.title = getTransformedText(tabStripItem.label.text, value);
	}

	public getTabBarHighlightColor(): UIColor {
		return this._ios.tabBar.tintColor;
	}

	public setTabBarHighlightColor(value: UIColor | Color) {
		this._ios.tabBar.tintColor = value instanceof Color ? value.ios : value;
	}

	public getTabBarSelectedItemColor(): Color {
		return this._selectedItemColor;
	}

	public setTabBarSelectedItemColor(value: Color) {
		this._selectedItemColor = value;
		this.updateAllItemsColors();
	}

	public getTabBarUnSelectedItemColor(): Color {
		return this._unSelectedItemColor;
	}

	public setTabBarUnSelectedItemColor(value: Color) {
		this._unSelectedItemColor = value;
		this.updateAllItemsColors();
	}

	public onMeasure(widthMeasureSpec: number, heightMeasureSpec: number): void {
		const width = layout.getMeasureSpecSize(widthMeasureSpec);
		const widthMode = layout.getMeasureSpecMode(widthMeasureSpec);

		const height = layout.getMeasureSpecSize(heightMeasureSpec);
		const heightMode = layout.getMeasureSpecMode(heightMeasureSpec);

		const widthAndState = View.resolveSizeAndState(width, width, widthMode, 0);
		const heightAndState = View.resolveSizeAndState(height, height, heightMode, 0);

		this.setMeasuredDimension(widthAndState, heightAndState);
	}

	public _onViewControllerShown(viewController: UIViewController) {
		// This method could be called with the moreNavigationController or its list controller, so we have to check.
		// TODO
		// if (Trace.isEnabled()) {
		//     Trace.write("TabView._onViewControllerShown(" + viewController + ");", Trace.categories.Debug);
		// }
		if (this._ios.viewControllers && this._ios.viewControllers.containsObject(viewController)) {
			this.selectedIndex = this._ios.viewControllers.indexOfObject(viewController);
		} else {
			// TODO
			// if (Trace.isEnabled()) {
			//     Trace.write("TabView._onViewControllerShown: viewController is not one of our viewControllers", Trace.categories.Debug);
			// }
		}
	}

	private _actionBarHiddenByTabView: boolean;
	public _handleTwoNavigationBars(backToMoreWillBeVisible: boolean) {
		// TODO
		// if (Trace.isEnabled()) {
		//     Trace.write(`TabView._handleTwoNavigationBars(backToMoreWillBeVisible: ${backToMoreWillBeVisible})`, Trace.categories.Debug);
		// }

		// The "< Back" and "< More" navigation bars should not be visible simultaneously.
		const page = this.page || (<any>this)._selectedView.page || (<any>this)._selectedView.currentPage;
		if (!page || !page.frame) {
			return;
		}

		const actionBarVisible = page.frame._getNavBarVisible(page);

		if (backToMoreWillBeVisible && actionBarVisible) {
			page.frame.ios._disableNavBarAnimation = true;
			page.actionBarHidden = true;
			page.frame.ios._disableNavBarAnimation = false;
			this._actionBarHiddenByTabView = true;

			// TODO
			// if (Trace.isEnabled()) {
			//     Trace.write(`TabView hid action bar`, Trace.categories.Debug);
			// }
			return;
		}

		if (!backToMoreWillBeVisible && this._actionBarHiddenByTabView) {
			page.frame.ios._disableNavBarAnimation = true;
			page.actionBarHidden = false;
			page.frame.ios._disableNavBarAnimation = false;
			this._actionBarHiddenByTabView = undefined;

			// TODO
			// if (Trace.isEnabled()) {
			//     Trace.write(`TabView restored action bar`, Trace.categories.Debug);
			// }
			return;
		}
	}

	private getViewController(item: TabContentItem): UIViewController {
		let newController: UIViewController = item.content ? item.content.viewController : null;

		if (newController) {
			(<any>item).setViewController(newController, newController.view);

			return newController;
		}

		if (item.content.ios instanceof UIViewController) {
			newController = item.content.ios;
			(<any>item).setViewController(newController, newController.view);
		} else if (item.content.ios && item.content.ios.controller instanceof UIViewController) {
			newController = item.content.ios.controller;
			(<any>item).setViewController(newController, newController.view);
		} else {
			newController = IOSHelper.UILayoutViewController.initWithOwner(new WeakRef(item.content)) as UIViewController;
			newController.view.addSubview(item.content.nativeViewProtected);
			item.content.viewController = newController;
			(<any>item).setViewController(newController, item.content.nativeViewProtected);
		}

		return newController;
	}

	private setViewControllers(items: TabContentItem[]) {
		const length = items ? items.length : 0;
		if (length === 0) {
			this._ios.viewControllers = null;

			return;
		}

		// Limit both tabContentItems and tabStripItems to 5 in order to prevent iOS 'more' button
		items = items.slice(0, maxTabsCount);

		const controllers = NSMutableArray.alloc<UIViewController>().initWithCapacity(length);

		if (this.tabStrip) {
			this.tabStrip.setNativeView(this._ios.tabBar);
		}

		items.forEach((item, i) => {
			const controller = this.getViewController(item);

			if (this.tabStrip && this.tabStrip.items && this.tabStrip.items[i]) {
				const tabStripItem = <TabStripItem>this.tabStrip.items[i];
				const tabBarItem = this.createTabBarItem(tabStripItem, i);
				updateTitleAndIconPositions(tabStripItem, tabBarItem, controller);

				this.setViewAttributes(tabBarItem, tabStripItem.label);

				controller.tabBarItem = tabBarItem;
				tabStripItem._index = i;
				tabStripItem.setNativeView(tabBarItem);
			}

			controllers.addObject(controller);
		});

		this.setItemImages();

		this._ios.viewControllers = controllers;
		this._ios.customizableViewControllers = null;

		// When we set this._ios.viewControllers, someone is clearing the moreNavigationController.delegate, so we have to reassign it each time here.
		this._ios.moreNavigationController.delegate = this._moreNavigationControllerDelegate;
	}

	private setItemImages() {
		if (this._selectedItemColor || this._unSelectedItemColor) {
			if (this.tabStrip && this.tabStrip.items) {
				this.tabStrip.items.forEach((item) => {
					if (this._unSelectedItemColor && item.nativeView) {
						item.nativeView.image = this.getIcon(item, this._unSelectedItemColor);
						item.nativeView.tintColor = this._unSelectedItemColor;
					}
					if (this._selectedItemColor && item.nativeView) {
						item.nativeView.selectedImage = this.getIcon(item, this._selectedItemColor);
						item.nativeView.tintColor = this._selectedItemColor;
					}
				});
			}
		}
	}

	public updateAllItemsColors() {
		this.setItemColors();
		if (this.tabStrip && this.tabStrip.items) {
			this.tabStrip.items.forEach((tabStripItem) => {
				this.updateItemColors(tabStripItem);
			});
		}
	}

	private updateItemColors(tabStripItem: TabStripItem): void {
		updateBackgroundPositions(this.tabStrip, tabStripItem);
		this.setIconColor(tabStripItem, true);
	}

	private createTabBarItem(item: TabStripItem, index: number): UITabBarItem {
		let image: UIImage;
		let title: string;

		if (item.isLoaded) {
			image = this.getIcon(item);
			title = item.label.text;

			const textTransform = item.label.style.textTransform;
			if (textTransform) {
				title = getTransformedText(title, textTransform);
			}
		}

		return UITabBarItem.alloc().initWithTitleImageTag(title, image, index);
	}

	private getIconRenderingMode(): UIImageRenderingMode {
		switch (this.tabStrip && this.tabStrip.iosIconRenderingMode) {
			case 'alwaysOriginal':
				return UIImageRenderingMode.AlwaysOriginal;
			case 'alwaysTemplate':
				return UIImageRenderingMode.AlwaysTemplate;
			case 'automatic':
			default:
				return UIImageRenderingMode.Automatic;
		}
	}

	private getIcon(tabStripItem: TabStripItem, color?: Color): UIImage {
		// Image and Label children of TabStripItem
		// take priority over its `iconSource` and `title` properties
		const iconSource = tabStripItem.image && tabStripItem.image.src;
		if (!iconSource) {
			return null;
		}

		const target = tabStripItem.image;
		const font = target.style.fontInternal || Font.default;
		if (!color) {
			color = target.style.color;
		}
		const iconTag = [iconSource, font.fontStyle, font.fontWeight, font.fontSize, font.fontFamily, color].join(';');

		let isFontIcon = false;
		let image: UIImage = this._iconsCache[iconTag];
		if (!image) {
			let is;
			if (isFontIconURI(iconSource)) {
				isFontIcon = true;
				const fontIconCode = iconSource.split('//')[1];
				is = ImageSource.fromFontIconCodeSync(fontIconCode, font, color);
			} else {
				is = ImageSource.fromFileOrResourceSync(iconSource);
			}

			if (is && is.ios) {
				image = is.ios;

				if (this.tabStrip && this.tabStrip.isIconSizeFixed) {
					image = this.getFixedSizeIcon(image);
				}

				let renderingMode: UIImageRenderingMode = UIImageRenderingMode.AlwaysOriginal;
				if (!isFontIcon) {
					renderingMode = this.getIconRenderingMode();
				}
				const originalRenderedImage = image.imageWithRenderingMode(renderingMode);
				this._iconsCache[iconTag] = originalRenderedImage;
				image = originalRenderedImage;
			} else {
				// TODO
				// traceMissingIcon(iconSource);
			}
		}

		return image;
	}

	private getFixedSizeIcon(image: UIImage): UIImage {
		const inWidth = image.size.width;
		const inHeight = image.size.height;

		const iconSpecSize = getIconSpecSize({
			width: inWidth,
			height: inHeight,
		});

		const widthPts = iconSpecSize.width;
		const heightPts = iconSpecSize.height;

		UIGraphicsBeginImageContextWithOptions({ width: widthPts, height: heightPts }, false, layout.getDisplayDensity());
		image.drawInRect(CGRectMake(0, 0, widthPts, heightPts));
		const resultImage = UIGraphicsGetImageFromCurrentImageContext();
		UIGraphicsEndImageContext();

		return resultImage;
	}

	// private _updateIOSTabBarColorsAndFonts(): void {
	//     if (!this.tabStrip || !this.tabStrip.items || !this.tabStrip.items.length) {
	//         return;
	//     }

	//     const tabBar = <UITabBar>this.ios.tabBar;
	//     const states = getTitleAttributesForStates(this);
	//     for (let i = 0; i < tabBar.items.count; i++) {
	//         applyStatesToItem(tabBar.items[i], states);
	//     }
	// }

	// TODO: Move this to TabStripItem
	// [fontInternalProperty.getDefault](): Font {
	//     return null;
	// }
	// [fontInternalProperty.setNative](value: Font) {
	//     this._updateIOSTabBarColorsAndFonts();
	// }

	[selectedIndexProperty.setNative](value: number): void {
		// TODO
		// if (Trace.isEnabled()) {
		//     Trace.write("TabView._onSelectedIndexPropertyChangedSetNativeValue(" + value + ")", Trace.categories.Debug);
		// }

		if (value > -1) {
			(<any>this._ios)._willSelectViewController = this._ios.viewControllers[value];
			this._ios.selectedIndex = value;
		}
	}

	[itemsProperty.getDefault](): TabContentItem[] {
		return null;
	}
	[itemsProperty.setNative](value: TabContentItem[]): void {
		if (value) {
			value.forEach((item: TabContentItem, i) => {
				(<any>item).index = i;
			});
		}

		this.setViewControllers(value);
		selectedIndexProperty.coerce(this);
	}

	[tabStripProperty.getDefault](): TabStrip {
		return null;
	}

	[tabStripProperty.setNative](value: TabStrip): void {
		this.setViewControllers(this.items);
		selectedIndexProperty.coerce(this);
	}

	private setViewAttributes(item: UITabBarItem, view: View): any {
		if (!view) {
			return null;
		}

		const defaultTabItemFontSize = 10;
		const tabItemFontSize = view.style.fontSize || defaultTabItemFontSize;
		const font: UIFont = (view.style.fontInternal || Font.default).getUIFont(UIFont.systemFontOfSize(tabItemFontSize));
		const tabItemTextColor = view.style.color;
		const textColor = tabItemTextColor instanceof Color ? tabItemTextColor.ios : null;
		const attributes: any = { [NSFontAttributeName]: font };

		// if selectedItemColor or unSelectedItemColor is set we don't respect the color from the style
		if (!this._selectedItemColor && !this._unSelectedItemColor) {
			if (textColor) {
				attributes[UITextAttributeTextColor] = textColor;
				attributes[NSForegroundColorAttributeName] = textColor;
			}
		} else {
			this.viewController.tabBar.unselectedItemTintColor = this._unSelectedItemColor && this._unSelectedItemColor.ios;
			this.viewController.tabBar.selectedImageTintColor = this._selectedItemColor && this._selectedItemColor.ios;
		}

		item.setTitleTextAttributesForState(attributes, UIControlState.Selected);
		item.setTitleTextAttributesForState(attributes, UIControlState.Normal);

		// there's a bug when setting the item color on ios 13 if there's no background set to the tabstrip
		// https://books.google.bg/books?id=99_BDwAAQBAJ&q=tabBar.unselectedItemTintColor
		// to fix the above issue we are applying the selected fix only for the case, when there is no background set
		// in that case we have the following known issue:
		// // we will set the color to all unselected items, so you won't be able to set different colors for the different not selected items
		if (!this.viewController.tabBar.barTintColor && attributes[UITextAttributeTextColor] && majorVersion > 9) {
			this.viewController.tabBar.unselectedItemTintColor = attributes[UITextAttributeTextColor];
		}
	}
}