Passing a listener to a custom Fragment in Android

user_5305817 0
Viewed 15759

I'm creating a view pager in my app and using a class that extends Fragment on it. When I create an instance I can pass all the elements (an image, text, etc) and store it with the Bundle to use it in the onCreate. But I can't store a listener for the button in the fragment. Here is my class:

public class RegWizardFragmentInfo extends Fragment {

private static final String IMAGE = "image";
private static final String TEXT = "text";
private static final String BUTTON = "buttonText";
private View.OnClickListener buttonCallBack;

private Button button;
private int image;
private int text;
private int buttonText;


public RegWizardFragmentInfo newInstance(int image, int text, int buttonText, View.OnClickListener callback) {

    RegWizardFragmentInfo fragment = new RegWizardFragmentInfo();
    Bundle bundle = new Bundle();
    bundle.putInt(IMAGE, image);
    bundle.putInt(BUTTON, buttonText);
    bundle.putInt(TEXT, text);
    fragment.setArguments(bundle);
    fragment.setRetainInstance(true);
    return fragment;

}

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    super.onActivityCreated(savedInstanceState);
    this.image = getArguments().getInt(IMAGE);
    this.text = (getArguments() != null) ? getArguments().getInt(TEXT)
            : -1;
    this.buttonText = (getArguments() != null) ? getArguments().getInt(BUTTON)
            : -1;
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    ViewGroup rootView = (ViewGroup) inflater.inflate(
            R.layout.fragment, container, false);
    //Extract all the views and add the image and texts

    return rootView;

}

So, how can I store the listener that I get in the newInstance to add it to the button on the onCreateView method?

Thanks for the help.

android-fragments fragment android java
3 Answers

You can use a callback in your Fragment:

public class RegWizardFragmentInfo extends Fragment {

    private Button button;

    private OnClickCallback callback;

    public interface OnClickCallback {
        void onClick();
    }

    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        callback = (OnClickCallback) context;
    }

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container,
                             @Nullable Bundle savedInstanceState) {
        return super.onCreateView(inflater, container, savedInstanceState);

        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                callback.onClick();
            }
        });
    }
}

and implement this new interface in your parent Activity

user_44026380

I suppose you want to re-use the Fragment with various different listeners. So your approach is not ideal since you can not use the Bundle for that. A better approach would be to use the callback design pattern e.g.

public class RegWizardFragmentInfo extends Fragment {

    public interface RegWizardCallback {
        void onClick();
    }
}

Your Activity would implement that interface. Since a Fragment only lives inside an Activity you can get the callback instance from it by using the lifecycle method onAttach(). It would look like this

public class RegWizardFragmentInfo extends Fragment {
    private RegWizardCallback callback;

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
        try {
            callback = (RegWizardCallback) activity;
        } catch (ClassCastException e) {
            throw new ClassCastException(activity.toString() + " must implement RegWizardCallback ");
        }
    }

    public interface RegWizardCallback {
        void onClick();
    }
}

With that you can simply call callback.onClick inside the listener of the Button.

user_44672080
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