transfer data from fragment to activity - keep getting null object returned

Question

I have a fragment that asks for email and password. I want to transfer the email to the activity.

I want to pass from the fragment the text from etCbMail, and then return to activity. I keep getting null object and i dont know how to return to the activity.

This is my fragment:

public class RegFragOne extends Fragment {

EditText etCbMail, etCbPassword, etCbVerifyPassword;
Button btnCbContinueToTwo;
OnDataPass dataPasser;

@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.reg_one, container, false);

    etCbMail = (EditText) view.findViewById(R.id.etEMail);
    etCbPassword = (EditText) view.findViewById(R.id.etPassword);
    etCbVerifyPassword = (EditText) view.findViewById(R.id.etVerifyPassword);
    btnCbContinueToTwo = (Button) view.findViewById(R.id.btnContinueToTwo);

    btnCbContinueToTwo.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            dataPasser.onDataPass(etCbMail.getText().toString());
        }
    });
    return view;
}

@Override
public void onAttach(Context context) {
    super.onAttach(context);
    try {
        dataPasser = (OnDataPass) context;
    } catch (Exception ex) {
        ex.printStackTrace();
    }
}

public interface OnDataPass {
    public void onDataPass(String data);
}
}

this is my activity:

public class RegistationActivity extends Activity implements RegFragOne.OnDataPass{
Fragment fragment;
FragmentTransaction fragmentTransaction;
String passedData;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.reg_fragment);

    fragment = new RegFragOne();
    fragmentTransaction = getFragmentManager().beginTransaction().add(R.id.frgContainer, fragment);
    fragmentTransaction.commit();


}

@Override
public void onDataPass(String data) {
    passedData = data;
}
}

and this is my log:

03-05 15:15:32.871 4043-4043/? E/AndroidRuntime: FATAL EXCEPTION: main
                                             Process: com.example.shaka.myparselogin, PID: 4043
                                             java.lang.NullPointerException: Attempt to invoke interface method 'void com.example.shaka.myparselogin.RegistrationFragments.RegFragOne$OnDataPass.onDataPass(java.lang.String)' on a null object reference
                                                 at com.example.shaka.myparselogin.RegistrationFragments.RegFragOne$1.onClick(RegFragOne.java:39)
                                                 at android.view.View.performClick(View.java:4756)
                                                 at android.view.View$PerformClick.run(View.java:19749)
                                                 at android.os.Handler.handleCallback(Handler.java:739)
                                                 at android.os.Handler.dispatchMessage(Handler.java:95)
                                                 at android.os.Looper.loop(Looper.java:135)
                                                 at android.app.ActivityThread.main(ActivityThread.java:5221)
                                                 at java.lang.reflect.Method.invoke(Native Method)
                                                 at java.lang.reflect.Method.invoke(Method.java:372)
                                                 at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
                                                 at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)

can you please help me with my 2 questions?

Answer 1

Replace getFragmentManager()... with getSupportFragmentManager().
This will force you to use the components from the support library ( Fragment, AppCompatActivity) and change your imports from import android.app.Fragment; to import android.support.v4.app.Fragment;.

As a general rule, try and use the components from the support libraries, not the ones from the framework, as the support components get bugs fixed faster. I have no proof to back this statement, only my day-to-day experience :).