Multiple Fragment Instances

Question

I have created a fragment I would like to add multiple instances of:

public class myFragment extends Fragment {
    int id;
    public static myFragment newInstance(int id) {
        myFragment fragment = new myFragment();
        int id = id;
        return fragment;
}

@Override
public View onCreateView(LayoutInflater inflater, final ViewGroup container,
                         Bundle savedInstanceState) {
     View rootView = inflater.inflate(R.layout.fragment_main, container, false);
     TextView idText = (TextView)
               rootView.findViewById(R.id.idText);
     idText.setText(id);
     return rootView;
}

In my Main class,

private int currentID;
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    if (savedInstanceState == null) {
       currentId = 0;
        FragmentManager manager = getFragmentManager();
        FragmentTransaction fragmentTransaction =  
                  manager.beginTransaction();
        oneFragment = new myFragment();
        oneFragment.newInstance(currentId);
        currentId = 2;
        fragmentTransaction
                .replace(R.id.container, oneFragment)
                .commit();
        twoFragment = new myFragment();
        twoFragment.newInstance(currentId);
        currentId = 3;

The problem is, oneFragment is coming up with id 2. I am not entirely sure why this is the case. The container is a LinearLayout with a vertical orientation and the Fragment is a linear as well. I would like to use the code I wrote for myFragment repeatedly for all of the ID's.

Answer 1

You should pass id for each Fragment using Constructor. So, every fragment instance hold their id in member variable

public class MyFragment extends Fragment {
    private int id;

    // constructor
    public MyFragment() {
    }

    public MyFragment(int a) {
        this.id = a;
    }

    // this method is not requreied if you use above Constuctor
    public myFragment newInstance(int id) {
        return new myFragment(id);
    }

}

Main Class :

private int currentID = 0;
    protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    if (savedInstanceState == null) {
       currentId = 0;
        FragmentManager manager = getFragmentManager();
        FragmentTransaction fragmentTransaction =  
                  manager.beginTransaction();
        oneFragment = new myFragment(currentID);  // id = 0

        currentId = 2;
        fragmentTransaction
                .replace(R.id.container, oneFragment)
                .commit();
        twoFragment = new myFragment(currentID);  // id = 2

        currentId = 3;
    }

Answer 2

Your MyFragment class needs to transfer the id like this:

public class MyFragment extends Fragment {

    private final static String ID_KEY = "id_key";
    public int id;

    public static MyFragment newInstance(int id) {
        MyFragment fragment = new MyFragment();
        Bundle args = new Bundle();
        args.putInt(ID_KEY, id);
        fragment.setArguments(args);
        return fragment;
    }

    public MyFragment() {
        // Required empty public constructor
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (getArguments() != null) {
            id = getArguments().getInt(ID_KEY);
        }
    }
}

I don't think that you need to create a fragment and then call newInstance() on it. I think you can just get away with calling newInstance(). Try this:

private int currentID;
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    if (savedInstanceState == null) {
       currentId = 0;
        FragmentManager manager = getFragmentManager();
        FragmentTransaction fragmentTransaction =  
                  manager.beginTransaction();
        MyFragment oneFragment = MyFragment.newInstance(currentId);
        currentId = 2;
        fragmentTransaction
                .replace(R.id.container, oneFragment)
                .commit();
        MyFragment twoFragment = MyFragment.newInstance(currentId);
        currentId = 3;