Android hardware back button is something one can easily forget about but must in the end be properly supported in any mobile application. Unfortunately, built-in support in Ionic 4 is less than perfect. Many scenarios are still not properly supported as documented in a GitHub issue which hasn't been resolved for almost a year.
Posts about Android
The final release of Ionic 4 is a good incentive for migrating existing Ionic 2/3 applications to Ionic 4. The official documentation lists the required steps for creating a new Ionic 4 project and adding Android support to it. If you're using Cordova 8+, then the application will run fine. But if you're still using Cordova 7.1.0, you'll only be greeted by a white screen when the application starts.
Cordova plugins can use variables for project specific values which must be entered when installing them. When these variables are used in Gradle build files for Android, a bug in Cordova 6.5.0 can cause the build to fail.
In a previous blogpost, I've described how to intercept console log output when the application is running on the device, so that it can later be exported using the standard sharing functionality. Although this is usually the most convenient approach for testers, it's an overkill during development. In such a scenario, it's more effective to look at the console output from the debugger.
Cordova has well documented support for modifying the contents of AndroidManifest.xml file from a plugin by adding config-file and edit-config elements to its plugin.xml file. It's less obvious that these same configuration elements can also be used directly inside the application's config.xml.
In native Android applications, the version of build tools and SDK to build them with can be specified directly in the Gradle build script. In Cordova applications, the build file is automatically generated, therefore any manual changes to it will be overwritten. The question is, where do the values in the generated file come from.
Ionic applications have built-in support for Android's hardware back button. For the root page it closes the application by default. There are ways to change that behavior, though.
I have finally updated Android SDK to the latest version, because I wanted Android Studio to stop informing me about available updates on every startup. Unfortunately several breaking changes have been introduced since the version I was using before, which altogether broke my regular flow of work.
Proguard is an optimizer and obfuscator for Java code. It can easily be enabled with only a few entries in the Gradle build script. In Cordova applications, the build script is regenerated on each build, therefore you'll need a plugin to add the required entries to it unless you want modify it by hand every time.
The official Android emulator has a big disadvantage for regular users of Hyper-V: you cannot run the emulator accelerated when Hyper-V is enabled. Fortunately, there is an alternative: Visual Studio Emulator for Android, which uses Hyper-V for hardware acceleration.
The book is a great first step into the world of Xamarin.Android for a seasoned .NET C# developer with no previous development experience on Android. It's definitely enough to get you started and makes it much easier to decide whether this is the right way to build Android applications or not.