在 Android 中，如何在单独的文件中获取 OnItemSelectedListener 中的 viewmodelprovider？

Question

I was trying to keep my code clean, so I wanted to put my OnItemSelectedListener methods in a separate file. This seems to work fine, I just define it like so:

public class spinnerSelected implements AdapterView.OnItemSelectedListener {
      public void onItemSelected(AdapterView<?> parent, View view, int pos, long id) {

Then in my mainActivity I set it like so:

spinner.setOnItemSelectedListener(new spinnerSelected());

This works fine, but now in this onItemSelectedListener i want to upated my viewModel adapter for MainActivity, but I can't figure out how to get to it. In the mainactivity I can get the model like so:

uiViewModel userModel  = ViewModelProviders.of(this).get(uiViewModel.class);

but in my spinnerSelected class I don't have the "this" and I couldn't find it in any of the passed in objects.

So is there a way to do this or am I doomed to just put my onItemSelectedListener in my main activity (which works fine)?

Thank you

Answer 1

You can pass your Activity or any other java object into your own spinnerSelected class. You just need to add a constructor. It will be called automatically when you create the new instance (which ensures it is never null). So the code would look something like this:

public class SpinnerSelected implements AdapterView.OnItemSelectedListener {
  Activity activity;

  SpinnerSelected (Activity activity){ //same name as class
    this.activity = activity
  }
      public void onItemSelected(AdapterView<?> parent, View view, int pos, long id) {
...

and

spinner.setOnItemSelectedListener(new spinnerSelected(this));