docs: fix broadcast receiver example + minor article improvements

app/ng-framework-modules-category/application/app-checking-target/article.md

@@ -1,4 +1,2 @@
-Use the following code in case you need to check somewhere in your code the platform you are running against:
-
-Basic usage of the `application` module in a component:
+Basic usage of the `application` module in a component to apply different code on Android and iOS
 <snippet id='app-check-target-code'/>

app/ng-framework-modules-category/application/app-using-android-specifics/app-using-android-specifics.component.ts

@@ -20,10 +20,24 @@ export class AppUsingAndroidExampleComponent {
             console.log("We are running on Android device!");
             this.isItemVisible = true;
 
+            // >> app-class-properties
+            // import { android as androidApp } from "tns-core-modules/application";
+            let isPaused = androidApp.paused; // e.g. false
+            let packageName = androidApp.packageName; // The package ID e.g. org.nativescript.nativescriptsdkexamplesng
+            let nativeApp = androidApp.nativeApp; // The native APplication reference
+            let foregroundActivity = androidApp.foregroundActivity; // The current Activity reference
+            let currentContext = androidApp.currentContext; // The current Android context
+            let context = androidApp.context; console.log(context); // The current Android context
+            // << app-class-properties
+
             // >> app-android-dirs-code
             this.fileList = [];
             this.appContext = androidApp.context;
+
+            // https://developer.android.com/reference/android/content/Context.html#getFilesDir()
             this.filesDir = this.appContext.getFilesDir();
+
+            // https://developer.android.com/reference/android/content/Context.html#getCacheDir()
             this.cacheDir = this.appContext.getCacheDir();
 
             let files = this.appContext.fileList();
@@ -37,8 +51,9 @@ export class AppUsingAndroidExampleComponent {
             this.batteryLife = "0";
             let that = this;
 
+            // Broadcast Receiver https://developer.android.com/reference/android/content/BroadcastReceiver
             androidApp.registerBroadcastReceiver(android.content.Intent.ACTION_BATTERY_CHANGED,
-                function onReceiveCallback(context: android.content.Context, intent: android.content.Intent) {
+                function onReceiveCallback(androidContext: android.content.Context, intent: android.content.Intent) {
                     let level = intent.getIntExtra(android.os.BatteryManager.EXTRA_LEVEL, -1);
                     let scale = intent.getIntExtra(android.os.BatteryManager.EXTRA_SCALE, -1);
                     let percent = (level / scale) * 100.0;
@@ -51,6 +66,12 @@ export class AppUsingAndroidExampleComponent {
             this.isItemVisible = false;
         }
     }
+
+    unregister() {
+        // >> app-android-broadcast-unregister-code
+        androidApp.unregisterBroadcastReceiver(android.content.Intent.ACTION_BATTERY_CHANGED);
+        // << app-android-broadcast-unregister-code
+    }
 }
 
 class File {

app/ng-framework-modules-category/application/app-using-android-specifics/article.md

@@ -1,5 +1,19 @@
-Using the Android Application context to get the absolute path to Files directory:
+### Application Module Android Specific Properties
+
+The application module provides a number of Android specific properties to access the Android app, context and activities.
+<snippet id='app-class-properties'/>
+
+### Using the Android Application Context
+
+In the extended example below, the Android context is used to get the absolute path to Files directory.
+We are accessing methods from the Android SDK (like `getCacheDir` and `getFilesDir`)
 <snippet id='app-android-dirs-code'/>
 
-Registering a Broadcast Receiver (Android)
-<snippet id='app-android-broadcast-code'/>
+### Registering a Broadcast Receiver (Android)
+
+NativeScript can send/receive messages and system information though broadcast receivers.
+More on broadcast receivers in Android [here](https://developer.android.com/guide/components/broadcasts).
+<snippet id='app-android-broadcast-code'/>
+
+### Unregistering a Broadcast Receiver (Android)
+<snippet id='app-android-broadcast-unregister-code'/>

app/ng-framework-modules-category/application/app-using-ios-specifics/app-using-ios-specifics.component.ts

@@ -15,6 +15,19 @@ export class AppUsingIosExampleComponent {
     constructor() {
 
         if (iosApp) {
+            // >> app-class-properties-ios
+            // import { ios as iosApp } from "tns-core-modules/application";
+
+            // https://developer.apple.com/documentation/uikit/uiapplicationdelegate?language=objc
+            let delegate = iosApp.delegate; // the iOS application delegate
+
+            let nativeApp = iosApp.nativeApp; // The native iOS app
+
+            // https://developer.apple.com/documentation/uikit/uiwindow/1621581-rootviewcontroller?language=objc
+            let rootController = iosApp.rootController; // the iOS rootViewController
+
+            let window = iosApp.window; // UIWindow
+            // << app-class-properties-ios
 
             this.isItemVisible = true;
             this.batteryLife = 0;

app/ng-framework-modules-category/application/app-using-ios-specifics/article.md

@@ -1,5 +1,10 @@
-Adding a Notification Observer (iOS)
+### Application Module iOS Specific Properties
+
+The application module provides a number of iOS specific properties to access the iOS app, delegate and root view controller, etc..
+<snippet id='app-class-properties-ios'/>
+
+### Adding a Notification Observer (iOS)
 <snippet id='app-ios-observer-code'/>
 
-Removing a notification observer
+### Removing a notification observer
 <snippet id='app-ios-observer-remove-code'/>