@@ -1,3 +1,4 @@
+import type { ApplicationEventData } from '../application';
 import * as Application from '../application';
 import { FontScaleCategory, getClosestValidFontScale } from './font-scale-common';
 export * from './font-scale-common';
@@ -12,7 +13,7 @@ function fontScaleChanged(origFontScale: number) {
 			eventName: Application.fontScaleChangedEvent,
 			object: Application,
 			newValue: currentFontScale,
-		});
+		} as ApplicationEventData);
 	}
 }
 
 
@@ -4,7 +4,6 @@ import '../globals';
 // Types
 import { AndroidApplication, iOSApplication } from '.';
 import { CssChangedEventData, DiscardedErrorEventData, LoadAppCSSEventData, UnhandledErrorEventData } from './application-interfaces';
-import { EventData } from '../data/observable';
 import { View } from '../ui/core/view';
 
 // Requires
@@ -50,10 +49,10 @@ export function setResources(res: any) {
 export const android: AndroidApplication = undefined;
 export const ios: iOSApplication = undefined;
 
-export const on = global.NativeScriptGlobals.events.on.bind(global.NativeScriptGlobals.events);
-export const off = global.NativeScriptGlobals.events.off.bind(global.NativeScriptGlobals.events);
-export const notify = global.NativeScriptGlobals.events.notify.bind(global.NativeScriptGlobals.events);
-export const hasListeners = global.NativeScriptGlobals.events.hasListeners.bind(global.NativeScriptGlobals.events);
+export const on = global.NativeScriptGlobals.events.on.bind(global.NativeScriptGlobals.events) as typeof import('.')['on'];
+export const off = global.NativeScriptGlobals.events.off.bind(global.NativeScriptGlobals.events) as typeof import('.')['off'];
+export const notify = global.NativeScriptGlobals.events.notify.bind(global.NativeScriptGlobals.events) as typeof import('.')['notify'];
+export const hasListeners = global.NativeScriptGlobals.events.hasListeners.bind(global.NativeScriptGlobals.events) as typeof import('.')['hasListeners'];
 
 let app: iOSApplication | AndroidApplication;
 export function setApplication(instance: iOSApplication | AndroidApplication): void {
@@ -63,7 +62,7 @@ export function setApplication(instance: iOSApplication | AndroidApplication): v
 }
 
 export function livesync(rootView: View, context?: ModuleContext) {
-	global.NativeScriptGlobals.events.notify(<EventData>{ eventName: 'livesync', object: app });
+	notify({ eventName: 'livesync', object: app });
 	const liveSyncCore = global.__onLiveSyncCore;
 	let reapplyAppStyles = false;
 
@@ -85,7 +84,7 @@ export function livesync(rootView: View, context?: ModuleContext) {
 
 export function setCssFileName(cssFileName: string) {
 	cssFile = cssFileName;
-	global.NativeScriptGlobals.events.notify(<CssChangedEventData>{
+	notify(<CssChangedEventData>{
 		eventName: 'cssChanged',
 		object: app,
 		cssFile: cssFileName,
@@ -98,7 +97,7 @@ export function getCssFileName(): string {
 
 export function loadAppCss(): void {
 	try {
-		global.NativeScriptGlobals.events.notify(<LoadAppCSSEventData>{
+		notify(<LoadAppCSSEventData>{
 			eventName: 'loadAppCss',
 			object: app,
 			cssFile: getCssFileName(),
@@ -181,7 +180,7 @@ export function setSuspended(value: boolean): void {
 }
 
 global.__onUncaughtError = function (error: NativeScriptError) {
-	global.NativeScriptGlobals.events.notify(<UnhandledErrorEventData>{
+	notify(<UnhandledErrorEventData>{
 		eventName: uncaughtErrorEvent,
 		object: app,
 		android: error,
@@ -191,7 +190,7 @@ global.__onUncaughtError = function (error: NativeScriptError) {
 };
 
 global.__onDiscardedError = function (error: NativeScriptError) {
-	global.NativeScriptGlobals.events.notify(<DiscardedErrorEventData>{
+	notify(<DiscardedErrorEventData>{
 		eventName: discardedErrorEvent,
 		object: app,
 		error: error,
 
@@ -13,22 +13,45 @@ export interface NativeScriptError extends Error {
 }
 
 export interface ApplicationEventData extends EventData {
+	/**
+	 * UIApplication or undefined, unless otherwise specified. Prefer explicit
+	 * properties where possible.
+	 */
 	ios?: any;
+	/**
+	 * androidx.appcompat.app.AppCompatActivity or undefined, unless otherwise
+	 * specified. Prefer explicit properties where possible.
+	 */
 	android?: any;
-	eventName: string;
+	/**
+	 * Careful with this messy type. A significant refactor is needed to make it
+	 * strictly extend EventData['object'], which is an Observable. It's used in
+	 * various ways:
+	 * - By font-scale: the Application module, typeof import('.')
+	 * - Within index.android.ts: AndroidApplication
+	 * - Within index.ios.ts: iOSApplication
+	 */
 	object: any;
 }
 
 export interface LaunchEventData extends ApplicationEventData {
+	/**
+	 * The value stored into didFinishLaunchingWithOptions notification's
+	 * userInfo under 'UIApplicationLaunchOptionsLocalNotificationKey';
+	 * otherwise, null.
+	 */
+	ios: unknown;
 	root?: View | null;
 	savedInstanceState?: any /* android.os.Bundle */;
 }
 
 export interface OrientationChangedEventData extends ApplicationEventData {
+	android: any /* globalAndroid.app.Application */;
 	newValue: 'portrait' | 'landscape' | 'unknown';
 }
 
 export interface SystemAppearanceChangedEventData extends ApplicationEventData {
+	android: any /* globalAndroid.app.Application */;
 	newValue: 'light' | 'dark';
 }
 
@@ -42,15 +65,14 @@ export interface DiscardedErrorEventData extends ApplicationEventData {
 	error: NativeScriptError;
 }
 
-export interface CssChangedEventData extends EventData {
+export interface CssChangedEventData extends ApplicationEventData {
 	cssFile?: string;
 	cssText?: string;
 }
 
-export interface AndroidActivityEventData {
+export interface AndroidActivityEventData extends ApplicationEventData {
 	activity: any /* androidx.appcompat.app.AppCompatActivity */;
-	eventName: string;
-	object: any;
+	object: any /* AndroidApplication */;
 }
 
 export interface AndroidActivityBundleEventData extends AndroidActivityEventData {
@@ -84,6 +106,6 @@ export interface RootViewControllerImpl {
 	contentController: any;
 }
 
-export interface LoadAppCSSEventData extends EventData {
+export interface LoadAppCSSEventData extends ApplicationEventData {
 	cssFile: string;
 }
@@ -4,7 +4,7 @@ import { AndroidActivityBackPressedEventData, AndroidActivityBundleEventData, An
 
 // TODO: explain why we need to this or remov it
 // Use requires to ensure order of imports is maintained
-const appCommon = require('./application-common');
+const appCommon = require('./application-common') as typeof import('./application-common');
 
 // First reexport so that app module is initialized.
 export * from './application-common';
 
@@ -257,21 +257,21 @@ export function _resetRootView(entry?: NavigationEntry | string);
 /**
  * Removes listener for the specified event name.
  */
-export function off(eventNames: string, callback?: (eventData: EventData) => void, thisArg?: any): void;
+export function off(eventNames: string, callback?: (eventData: ApplicationEventData) => void, thisArg?: any): void;
 
 /**
  * Shortcut alias to the removeEventListener method.
  * @param eventNames - String corresponding to events (e.g. "onLaunch").
  * @param callback - Callback function which will be removed.
  * @param thisArg - An optional parameter which will be used as `this` context for callback execution.
  */
-export function off(eventNames: string, callback?: (eventData: EventData) => void, thisArg?: any): void;
+export function off(eventNames: string, callback?: (eventData: ApplicationEventData) => void, thisArg?: any): void;
 
 /**
  * Notifies all the registered listeners for the event provided in the data.eventName.
  * @param data The data associated with the event.
  */
-export function notify(data: any): void;
+export function notify<T extends ApplicationEventData>(data: T): void;
 
 /**
  * Checks whether a listener is registered for the specified event name.
@@ -295,18 +295,13 @@ export function on(event: 'cssChanged', callback: (args: CssChangedEventData) =>
 /**
  * Event raised then livesync operation is performed.
  */
-export function on(event: 'livesync', callback: (args: EventData) => void, thisArg?: any): void;
+export function on(event: 'livesync', callback: (args: ApplicationEventData) => void, thisArg?: any): void;
 
 /**
  * This event is raised when application css is changed.
  */
 export function on(event: 'cssChanged', callback: (args: CssChangedEventData) => void, thisArg?: any): void;
 
-/**
- * Event raised then livesync operation is performed.
- */
-export function on(event: 'livesync', callback: (args: EventData) => void, thisArg?: any): void;
-
 /**
  * This event is raised on application launchEvent.
  */
@@ -317,7 +312,7 @@ export function on(event: 'launch', callback: (args: LaunchEventData) => void, t
  * Its intent is to be suitable for measuring app startup times.
  * @experimental
  */
-export function on(event: 'displayed', callback: (args: EventData) => void, thisArg?: any): void;
+export function on(event: 'displayed', callback: (args: ApplicationEventData) => void, thisArg?: any): void;
 
 /**
  * This event is raised when the Application is suspended.
 
@@ -4,15 +4,14 @@ import { ApplicationEventData, CssChangedEventData, LaunchEventData, LoadAppCSSE
 
 // TODO: explain why we need to this or remov it
 // Use requires to ensure order of imports is maintained
-const { backgroundEvent, displayedEvent, exitEvent, foregroundEvent, getCssFileName, launchEvent, livesync, lowMemoryEvent, notify, on, orientationChanged, orientationChangedEvent, resumeEvent, setApplication, suspendEvent, systemAppearanceChanged, systemAppearanceChangedEvent } = require('./application-common');
+const { backgroundEvent, displayedEvent, exitEvent, foregroundEvent, getCssFileName, launchEvent, livesync, lowMemoryEvent, notify, on, orientationChanged, orientationChangedEvent, resumeEvent, setApplication, suspendEvent, systemAppearanceChanged, systemAppearanceChangedEvent } = require('./application-common') as typeof import('./application-common');
 // First reexport so that app module is initialized.
 export * from './application-common';
 
 import { View } from '../ui/core/view';
 import { NavigationEntry } from '../ui/frame/frame-interfaces';
 // TODO: Remove this and get it from global to decouple builder for angular
 import { Builder } from '../ui/builder';
-import { Observable } from '../data/observable';
 import { CSSUtils } from '../css/system-classes';
 import { IOSHelper } from '../ui/core/view/view-helper';
 import { Device } from '../platform';
@@ -238,7 +237,7 @@ export class iOSApplication implements iOSApplicationDefinition {
 		const args: LaunchEventData = {
 			eventName: launchEvent,
 			object: this,
-			ios: (notification && notification.userInfo && notification.userInfo.objectForKey('UIApplicationLaunchOptionsLocalNotificationKey')) || null,
+			ios: notification?.userInfo?.objectForKey('UIApplicationLaunchOptionsLocalNotificationKey') || null,
 		};
 
 		notify(args);
 
@@ -25,17 +25,7 @@ declare namespace NodeJS {
 			 * Global framework event handling
 			 */
 			events: {
-				on(eventNames: string, callback: (data: any) => void, thisArg?: any);
-				on(event: 'propertyChange', callback: (data: any) => void, thisArg?: any);
-				off(eventNames: string, callback?: any, thisArg?: any);
-				addEventListener(eventNames: string, callback: (data: any) => void, thisArg?: any);
-				removeEventListener(eventNames: string, callback?: any, thisArg?: any);
-				set(name: string, value: any): void;
-				setProperty(name: string, value: any): void;
-				get(name: string): any;
-				notify<T>(data: any): void;
-				notifyPropertyChange(propertyName: string, value: any, oldValue?: any): void;
-				hasListeners(eventName: string): boolean;
+				[Key in keyof import('data/observable').Observable]: import('data/observable').Observable[Key];
 			};
 			launched: boolean;
 			// used by various classes to setup callbacks to wire up global app event handling when the app instance is ready
Original file line number	Diff line number	Diff line change
`@@ -1,3 +1,4 @@`
	`1`	`+import type { ApplicationEventData } from '../application';`
`1`	`2`	`import * as Application from '../application';`
`2`	`3`	`import { FontScaleCategory, getClosestValidFontScale } from './font-scale-common';`
`3`	`4`	`export * from './font-scale-common';`
`@@ -12,7 +13,7 @@ function fontScaleChanged(origFontScale: number) {`
`12`	`13`	`eventName: Application.fontScaleChangedEvent,`
`13`	`14`	`object: Application,`
`14`	`15`	`newValue: currentFontScale,`
`15`		`- });`
	`16`	`+ } as ApplicationEventData);`
`16`	`17`	`}`
`17`	`18`	`}`
`18`	`19`