如何在 RecyclerView.Adapter 类中创建警报对话框构建器

Question

HoAlertDialogBuilder in my RecylerView.Adapater class i get an error saying "in Builder cannot to the com.example.john.atsnotify.Adapter.PupilGroupAdapter class"

i can easily create an alert dialog Builder in a regular activity class which extends AppCompatActivity but not in an Adapter class. why?

https://pastebin.com/WqXCG1Ch AlertDialog.Builder builder = new AlertDialog.Builder(PupilGroupAdapter.this);

Answer 1

The argument to the constructor (for which you are currently passing PupilGroupAdapter.this ) must be of type Context . Your adapter is not a Context, so this is failing.

You can retrieve a context from any View instance via the getContext() method. In your case, you're trying to show the alert dialog from a button click, so you can use the context of the view passed to the click listener:

@Override
public void onBindViewHolder(@NonNull ViewHolder viewHolder, int i) {
    // ...

    viewHolder.btnAdd.setOnClickListener( new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            showAlertDialog(view.getContext()); // pass the context here
        }
    } );
}

private void showAlertDialog(Context context) { // receive the context here
    AlertDialog.Builder builder = new AlertDialog.Builder(context); // use the context here
}

Answer 2

Was looking for a similar way and Context did not help. Found a solution through chat history of https://chat.stackoverflow.com/rooms/110530/discussion-between-sukhbir-and-amir-p

Implemented it in my code with Adapter constructor parameter like so:

public AdapterClass(..., Activity abc, ...){
  this.abc = abc;
}

In my activity class initiating the recycler adapter:

AdapterClass newAdapter = new AdapterClass(..., CurrentActivity.this, ...);

And alert dialog in RecyclerAdapter onBindViewHolder class:

public void startAlert(..., Activity passedActivity, ...){
  AlertDialog.Builder aB = new AlertDialog.Builder(passedActivity);
  ...
}