Unable to launch another activity from fragment in android studio

Question

I have a fragment in which I am trying to call a new activity on a button click.

 btnLoadLimit.setOnClickListener(v -> {
        Intent intent = new Intent(getActivity(), DataActivity.class);
        startActivity(intent);
    });

Data Activity

public class DataActivity extends AppCompatActivity {
 Context mContext;

 @BindView(R.id.smart_msn_spinner)
Spinner msnSpinner;

 ArrayList<String> msnArrayList = new ArrayList<>(Arrays.asList("Select MSN","002998002010" )); //"002999002020"

ArrayAdapter<String> msnAdapter;

 @Override
 protected void onCreate(Bundle savedInstanceState) {


  msnAdapter = new ArrayAdapter<>(mContext, android.R.layout.simple_spinner_dropdown_item, msnArrayList);
    msnSpinner.setAdapter(msnAdapter);
    msnSpinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
        @Override
        public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
            selectedMeterNo = msnArrayList.get(position);
        }

        @Override
        public void onNothingSelected(AdapterView<?> parent) {

        }
    });
        
 }

}

When I click on btnLoadLimit button my app is closing with the following error

Unable to start activity ComponentInfo{com.thumbsol.accuratemobileassetsmanagament/com.thumbsol.accuratemobileassetsmanagament.fragment.DataActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object android.content.Context.getSystemService(java.lang.String)' on a null object reference

at com.thumbsol.accuratemobileassetsmanagament.fragment.DataActivity.onCreate(DataActivity.java:122)

The line 122 is msnAdapter = new ArrayAdapter<>(mContext, android.R.layout.simple_spinner_dropdown_item, msnArrayList);

The same method I have applied in my fragment and it's working but in my new activity it's not.

Note: The activity is displaying if none of the methods are invoked.

Answer 1

Looks like you don't initialize your mContext . meaning you're passing null to your ArrayAdapter().

You shouldn't be storing your context anyway, since your context is your activity.. You can just use this :

msnAdapter = new ArrayAdapter<>(this, android.R.layout.simple_spinner_dropdown_item, msnArrayList);