How to access packagemanager in viewmodel-CodePudding

I was using fragment and now I attached ViewModel to it and was transferring code to ViewModel and activity?.packageManager?.getPackageInfo(uri, PackageManager.GET_ACTIVITIES) this line shows an error. How can I access package manager in ViewModel?

CodePudding user response：

On way is to extend AndroidViewModel instead of ViewModel as:

class MyFragmentViewModel(application: Application) : AndroidViewModel(application) {
...

Now you can call:

application.packageManager?.getPackageInfo(uri, PackageManager.GET_ACTIVITIES)

CodePudding user response：

Theoretically if you are implementing MVVM pattern (I see you implementing ViewModel), android.* layer should be handled in the View, Activities/Contexts shouldn't be managed in the ViewModel to avoid Memory Leaks. Even though, depending on the project context, of course this rule doesn't apply to every single project context, I think the best approach would be (if not Dependency Injection is been used) to have an Application Provider.

Create an object:

object ApplicationProvider {

    @Volatile
    lateinit var application: Application

    fun initialize(_application: Application) {
        if (!::application.isInitialized) {
            synchronized(this) {
                application = _application
            }
        }
    }
}

In your MainActivity, initialise the ApplicationProvider as the following:

override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding = ActivityMainBinding.inflate(layoutInflater)
        setContentView(binding.root)
        
        ApplicationProvider.initialize(this.application)
    }

Now you can access the ApplicationContext in your whole project where is needed with:

ApplicationProvider.application.applicationContext

Remember to not assign ApplicationContext to static fields (as a val e.g.) to avoid Memory Leaks.

PD: I'm not very fan of AndroidViewModel, but I guess it is a good solution as well, as a colleague mentioned before :D