Start Activity within a fragment

Question

I'm trying to start a new Tab1City activity, as I click on a button from Tab1Discover, which is a fragment. I've try several combinaisons if parameters, looking on stackoverflow, but it keeps compiling and making the app crash at launch, with a :

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference

at Tab1Discover.onCreateView(Tab1Discover.java:32)

public class Tab1Discover extends Fragment {

@InjectView(R.id.buttonLille)
Button _loginButton;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {


    _loginButton.setOnClickListener(new View.OnClickListener(){
        @Override
        public void onClick(View v) {
            // Start the Signup activity
            Intent intent = new Intent(getActivity(), Tab1City.class);
            startActivity(intent);
        }
    });


    return inflater.inflate(R.layout.tab_1_disc1_main, container, false);
}
}

score 2 · Answer 1 · edited May 23 '17 at 11:44

2

Edit:

I've noticed (thanks to the comment) that you're using RoboGuice. After a quick search, I've come up that the reference will only be available in onViewCreated, so move your code there:

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
  return inflater.inflate(R.layout.tab_1_disc1_main, container, false);
}


@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
  super.onViewCreated(view, savedInstanceState);
  _loginButton.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
      // Start the Signup activity
      Intent intent = new Intent(getActivity(), Tab1City.class);
      startActivity(intent);
    }
  });
}

edited May 23 '17 at 11:44

Community

1
1

answered Oct 12 '15 at 20:12

Simas

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His `@InjectView (R.id.idhere) CLASS varname;` is perfectly valid. Shouldn't he still inflate the xml before using the variable if he uses `@InjectView`? If not, then it could simply be that `R.id.buttonLille` isn't existent. – showp1984 Oct 12 '15 at 20:14
@showp1984 thanks for the insight. I've updated the answer accordingly. – Simas Oct 12 '15 at 20:18
Android Studio says to me that types are incompatibles, as _loginButton is a button, and it found that R.id.buttonLille is a view – Adrien Chapelet Oct 12 '15 at 20:19
@AdrienChapelet you will need RoboGuice if you are going to use `@InjectView`. See: https://github.com/roboguice/roboguice/ – showp1984 Oct 12 '15 at 20:21
1

@AdrienChapelet if you're talking about my old answer, you need to cast it using `... = (Button) ...` – Simas Oct 12 '15 at 20:21

score 0 · Answer 2 · answered Oct 12 '15 at 20:17

From your usage of '@InjectView', i'm guessing you're using ButterKnife 6.0.x.

You're missing the part of ButterKnife where you have to tell it WHEN to inject the views.

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.tab_1_disc1_main, container, false);

    ButterKnife.inject(this, rootView);

    _loginButton.setOnClickListener(new View.OnClickListener(){
        @Override
        public void onClick(View v) {
            // Start the Signup activity
            Intent intent = new Intent(getActivity(), Tab1City.class);
            startActivity(intent);
        }
    });

    return rootView;
}

With this code, you're telling ButterKnife where to find the view so it can set up the bindings. From here on, you can simply add all the @InjectView you want, and it'll take care of the bindings automatically.

score 0 · Answer 3 · answered Oct 12 '15 at 20:30

Thanks a lot, that's now working :

public class Tab1Discover extends Fragment {

@InjectView(R.id.buttonLille)
Button _lilleButton;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.tab_1_disc1_main, container, false);

    ButterKnife.inject(this, rootView);

    _lilleButton.setOnClickListener(new View.OnClickListener(){
        @Override
        public void onClick(View v) {
            // Start the Signup activity
            Intent intent = new Intent(getActivity(), Tab1City.class);
            startActivity(intent);
        }
    });

    return rootView;
}

Start Activity within a fragment

3 Answers3