Migrating NativeScript Plugins to AndroidX


The NativeScript 6.0 release is planned for July and with it comes support for AndroidX. We are also dropping support for the Android Support Library which is a breaking change and means code depending on it should be migrated.

This blog will provide what you, as a plugin developer, can do to prepare for the release.

Important: NativeScript 6 projects will build with both useAndroidX and enableJetifier enabled. Which means that all existing libraries (.jar and .aar files you ship with or include in your plugins) will be automatically migrated by jetifier at build time.

That said, each NativeScript plugin falls in one of following categories:

  1. There is no need to migrate the plugin. YEY!
  2. Plugin can be made compatible with both support-lib and AndroidX.
  3. There is no compatibility path (or it's just not worth it). You should publish an AndroidX-only version of the plugin to make it usable with NativeScript 6.0.

Let's see what is the recommended way to go forward in each case.

No Need To Migrate

Example: nativescript-localstorage

If your plugin (and its dependencies) does not depend on the Android Support Library in any way - you are off the hook. You can stop reading now.

Also, if the plugin uses a third-party native library that depends on support-lib, but does not use the support lib API in the JS/TS code - there is a good chance that you don't have to do anything. Jetifier will migrate the library build-time for you. Of course it is always best to test if you are not sure.

Versioning

There is no need to release new version of the plugin in this case.

Make it Compatible with Both Support-lib and AndroidX

Example: nativescript-permissions

In many cases it is possible to make your plugin compatible with both support-lib and AndroidX by performing a runtime check to know which one is available. You can check this awesome blog by Nathanael Anderson on how to do that. He's got (and maintains) tons of high quality plugins so you can trust him 😉.

There are some cases when re-writing your code to be compatible will take more effort. Mainly, when you are extending classes from the support lib. Here is an example on how to do that:

function useAndroidX {
    return global.androidx && global.androidx.appcompat;
};

function getMyClass() {
    if (useAndroidX()) {
        // Class implementation using AndroidX
        class MyCardView extends androidx.cardview.widget.CardView {
            // implementation skipped for brevity 
        }

        return MyCardView;
    } else {
        // Class implementation using support-lib
        class MyCardView extends android.support.v7.widget.CardView {
            // implementation skipped for brevity 
        }    

        return MyCardView;
    }
}

// Get the final class
const MyCardViewClass = getMyClass();

What?! But, I have so many questions!

Yup! The code above looks strange. Let's try to address some of the questions.

1. How does the Static Binding Generator (SBG) know for which of the two implementations to generate bindings?

SBG will try to generate bindings for both. However, it will only succeed for implementations that extends a class that it knows about at build time (libraries that you are referenced in the Android poject). So if you are building for NativeScript 5 - it will have the support-lib in its context and will manage to generate a class extending android.support.v7.widget.CardView.It will not generate bindings for the implementation extending androidx.cardview.widget.CardView. The opposite is true when building for NativeScript 6. The useAndroidX() check will make sure you use the right implementation at runtime.

Important: SBG will match the class in the extends directly. As it doesn't actually evaluate the JS code you are not allowed to put dynamic code there. So, the following will not work:

const supportLib = global.androidx ? androidx.cardview.widget : extends android.support.v7.widget;
class MyCardView extends supportLib.CardView { ... }

2. Looks like a lot of duplicating code?

You might try to share some of the code by extracting it outside the implementation of the classes. But...yeah, your code will get less pretty.

3. What about TypeScript definitions?

You can use the androidx tag of tns-platform-declarations to get AndroidX typings (npm i tns-platform-declarations@androidx). It will give you the definitions for types in AndroidX, but you won't get definitions for support-lib. You might want to use <any> or "stub" for one of the flavors (ex. declare var androidx:any;)

Versioning

Once you're done with migration, you can safely publish these changes as a minor or patch release of the plugin. The good part is that you can do this now and your plugin will be usable with NativeScript 6 when it comes out.

No Compatibility Path

Example: tns-core-modules

It might just not be possible for your plugin to be compatible with both support-lib and AndroidX. This can be due to multiple reasons:

  • Java code or third party lib depends on support-lib (and for some reason jetifier cannot handle it).
  • You are extending support-lib classes in your JS code and you don't want to bloat your code with androix runtime checks.
  • You have support lib configuration in android-manifest.xml or other resource that cannot be handled by jetifier.

There are some tools that might help you with the migration. You can use jetifier-standalone tool for the native dependencies and/or androidx-migration-tool for your JS/TS/Java code. You can also check support for AndroidX in NativeScript for tips on migration.

Versioning

Here is the recommended action plan:

  1. Migrate the plugin.
  2. Bump a major version and publish it behind androidx tag in npm: $npm publish --tag androidx
  3. (When NativeScript 6.0 is released) Publish the AndroidX version. It's a good idea to add a peerDependency to "tns-core-modules": ">6.0.0".

Note: Publishing behind the androidx tag before the official NativeScript 6 release will give a chance to other plugins and applications that depend on it to be tested.

Test Your Plugin Now!

Regardless of which category your plugin falls into, it is highly recommended to test it now using the androidx builds of the android-runtime and tns-core-modules:

npm install tns-core-modules@androidx --save-exact
tns platform add android@androidx
npm install tns-platform-declarations@androidx --save-exact (if you need typings)

You can then run your demo projects to assure everything is working as expected.

Getting Help

Handling breaking changes can be tedious, but we are here to help. Reach out to us in the NativeScript slack - #androidx-migration channel if you get stuck.

alex vakrilov
Author

Alexander Vakrilov

Alex is the team lead of the NativeScript core modules team and co-organizer of Angular Sofia meetup. He is passionate about optimizing code, making functions pure and keeping state immutable.

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