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I'm having this error 'Cannot resolve constructor 'ArrayAdapter( anonymous com.google.firebase.database.ValueEventListener...'

Here is my code

public class TestingActivity extends AppCompatActivity {
Button btnOpen;
Spinner spin2;
private Context mContext;
//private HashMap<String ,String> volName = new HashMap<>();
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_testing);

    Firebase.setAndroidContext(this);
    mContext = this;

    btnOpen = (Button)findViewById(R.id.btnOpen);
    spin2 = (Spinner)findViewById(R.id.spinner2);

    Log.d("TAG", "First click");

    //Add countries
    // Spinner example

    // read fireabse again. pfftt
    DatabaseReference volRef = FirebaseDatabase.getInstance().getReference("users");
    Query queryRef = volRef.orderByChild("role").equalTo("Volunteer");
    Log.d("TAG", "Second click");

    queryRef.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            HashMap<String ,String> volName = new HashMap<>();
            for (DataSnapshot s : dataSnapshot.getChildren()) {
                final Person listLoc = s.getValue(Person.class);
                Log.d("TAG", "Family Name " + listLoc.getEmail() );
                volName.put(listLoc.getEmail(), listLoc.getFirstname() + " " + listLoc.getSurname());

            }
            // Create the ArrayAdapter
            ArrayAdapter<HashMap<String ,String>> arrayAdapter = new ArrayAdapter<HashMap<String, String>>( TestingActivity.this,android.R.layout.simple_spinner_dropdown_item,volName);
            // Set the Adapter
            spin2.setAdapter(arrayAdapter);


        }



        @Override
        public void onCancelled(DatabaseError databaseError) {

        }


}

I have use TestingActivity.this, getActivity, this, getApplicationContext, Context but the error is still the same. Can anyone guide me through this. Thanks

Shafiq Mustapa
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  • yes. I have updated the code. – Shafiq Mustapa Oct 25 '18 at 13:11
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    I am not sure if an `ArrayAdapter` is properly working with a `Map`, [this](https://developer.android.com/reference/android/widget/ArrayAdapter) states that it will accept `List` and `T[]`, no talk about a `Map`. I mean the `volName`... The error message says that it `Cannot resolve constructor...`. – deHaar Oct 25 '18 at 13:14
  • Finally, [this question here on stackoverflow](https://stackoverflow.com/questions/5234576/what-adapter-shall-i-use-to-use-hashmap-in-a-listview) might help you (a lot if you understand it). You obviously cannot use an `ArrayAdapter` and pass a `Map` to it because it cannot handle `Map`s. To be able to pass a `Map` to an adapter, you will have to implement one yourself, which is possible. – deHaar Oct 25 '18 at 13:21
  • Possible duplicate of [What adapter shall I use to use HashMap in a ListView](https://stackoverflow.com/questions/5234576/what-adapter-shall-i-use-to-use-hashmap-in-a-listview) – deHaar Oct 25 '18 at 13:23
  • i think it is quite possible to pass a map – Avinash Roy Oct 25 '18 at 13:26
  • I will look into it. Need to look into Firebase UI solutions. Thanks for the help @deHaar – Shafiq Mustapa Oct 25 '18 at 13:27
  • @ShafiqMustapa no problem, please also check if you are passing the correct context, wich may be another error source. – deHaar Oct 25 '18 at 13:29
  • Check **[this](https://stackoverflow.com/questions/48622480/showing-firebase-data-in-listview)** out. – Alex Mamo Oct 26 '18 at 05:33

1 Answers1

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Pass Activity Context instance as first parameter to your ArrayAdapter. Currently you are passing ValueEventListener instance.

 // Set the Adapter
 ArrayAdapter<HashMap<String ,String>> arrayAdapter = new ArrayAdapter<HashMap<String, String>>( TestingActivity.this,android.R.layout.simple_spinner_dropdown_item,volName);

also you are passing wrong third parameter. You can pass only List or Array. You can not pass single HashMap. You need to pass List or Array of HashMap.

Chandrakant Dvivedi
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