Can't replace a fragment by another one

Question

Even though I've been reading other topics about my kind of problem, I can't figure out the reason of my problem.

I have an activity where there is on the left a ListView. On the right is a ListFragment as you can see it on the activity_question.xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="0dip"
        android:layout_weight="1"
        android:orientation="horizontal" >

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_weight="3"
            android:orientation="vertical" >

            <TextView
                android:id="@+id/textViewCategoryTitle"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_gravity="center"
                android:layout_weight="10"
                android:background="@drawable/in_progress_background"
                android:gravity="center" />

            <ListView
                android:id="@+id/listViewQuestionsGroup"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:layout_weight="1" />
        </LinearLayout>

        <fragment
            android:id="@+id/fragmentQuestions"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_weight="1"
            class="com.firm.bonjour.visite.QuestionsFragment" />
    </LinearLayout>

    <Button
        android:id="@+id/buttonValidate"
        style="@style/ButtonsValidation"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|right"
        android:text="@string/validate" />

</LinearLayout>

I have created an Adapter for the ListView of the Fragment:

public class QuestionsAdapter extends BaseAdapter {

    private QuestionsBean questions = null;
    private LayoutInflater inflater = null;

    public QuestionsAdapter(LayoutInflater inflater) {
        this.inflater = inflater;
    }

    @Override
    public int getCount() {
        return (questions != null && questions.getQuestionList() != null) ? questions.getQuestionList().size() : 0;
    }

    @Override
    public Object getItem(int position) {
        return (questions != null && questions.getQuestionList() != null) ? questions.getQuestionList().get(position) : null;
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder holder;

        if (convertView == null) {
            holder = new ViewHolder();

            convertView = inflater.inflate(R.layout.item_fragment_question, null);

            holder.question = (TextView) convertView.findViewById(R.id.questionsLayout);

            convertView.setTag(holder);

        } else {
            holder = (ViewHolder) convertView.getTag();
        }

        holder.question.setText(((QuestionsBean) questions).getQuestionList().get(position).getQuestion());

        return convertView;
    }

    private class ViewHolder {
        TextView question;
    }

    public void setQuestions(QuestionsBean questions) {
        this.questions = questions;
        notifyDataSetChanged();
    }

}

When I start the Activity, I select the first item on the left side ListView to display detail in the Fragment. Once I click on one of the items of my left side ListView, the Fragment doesn't change. When I'm in debugg mod, I can see that the Adapter get the right object to display.

Do you have any idea why the new Fragment isn't displaying ?

My Activity code:

public class QuestionsActivity extends Activity implements OnItemClickListener {

    public static final String QUESTIONS_LIST = "questionsList";
    public static final String QUESTIONS = "questions";

    private CategoryBean category;

    private ListView questionsGroupListView;

    private Fragment questionsFragment;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_questions);

        category = (CategoryBean) getIntent().getExtras().get(MainActivity.CATEGORY);

        questionsGroupListView = (ListView) findViewById(R.id.listViewQuestionsGroup);
        QuestionListAdapter adapter = new QuestionListAdapter(this, category);
        questionsGroupListView.setAdapter(adapter);
        questionsGroupListView.setOnItemClickListener(this);

        if (getFragmentManager().findFragmentById(R.id.fragmentQuestions) == null) {
            questionsFragment = new QuestionsFragment();
            getFragmentManager().beginTransaction().add(R.layout.activity_questions, questionsFragment).commit();
        } else {
            questionsFragment = getFragmentManager().findFragmentById(R.id.fragmentQuestions);
        }
    }

    /**
     * Called when a number gets clicked
     */
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        displayFragment((QuestionsBean)questionsGroupListView.getItemAtPosition(position));
    }

    @Override
    protected void onResume() {
        super.onResume();
        if(questionsFragment != null && category.getCategoryList() != null && !category.getCategoryList().isEmpty()) {
            ((QuestionsFragment)questionsFragment).refresh((QuestionsBean)category.getCategoryList().get(0));
        } else {
            Log.v("BUGGGGG", "PAS NORMAL !!!");
        }
    }

    /**
     * Add a Fragment to our stack with n Androids in it
     */
    private void displayFragment(QuestionsBean questions) {
        Fragment fragment = QuestionsFragment.newInstance(questions);

        FragmentTransaction fragmentTransaction = getFragmentManager().beginTransaction();
        fragmentTransaction.replace(R.id.fragmentQuestions, fragment);
        fragmentTransaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
        fragmentTransaction.commit();
    }

}

My ListFragment code:

public class QuestionsFragment extends ListFragment {

    private LayoutInflater inflater;
    private QuestionsAdapter adapter;
    private QuestionsBean questions;

    /**
     * Create a new instance of DetailsFragment, initialized to show the text at 'index'.
     */
    public static QuestionsFragment newInstance(QuestionsBean questions) {
        QuestionsFragment questionFragment = new QuestionsFragment();

        // Supply index input as an argument.
        Bundle args = new Bundle();
        args.putSerializable(QuestionsActivity.QUESTIONS, questions);
        questionFragment.setArguments(args);

        return questionFragment;
    }

    public int getShownIndex() {
        return getArguments() != null ? getArguments().getInt("index", 0) : 0;
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        this.inflater = inflater;
        this.adapter = new QuestionsAdapter(inflater);

        View questionsView = (LinearLayout) inflater.inflate(R.layout.layout_fragment_question, null);
        setListAdapter(adapter);

        return questionsView;
    }

    @Override
    public void onResume() {
        super.onResume();
        if (getArguments() != null && getArguments().getSerializable(QuestionsActivity.QUESTIONS) != null) {
            this.questions = (QuestionsBean) getArguments().getSerializable(QuestionsActivity.QUESTIONS);
            adapter.setQuestions((QuestionsBean) getArguments().getSerializable(QuestionsActivity.QUESTIONS));
        } else {
            adapter.setQuestions(questions);
        }
    }

    @Override
    public void onListItemClick(ListView l, View v, int position, long id) {
        super.onListItemClick(l, v, position, id);

    }

    public void refresh(QuestionsBean questions) {
        if (getArguments() != null && getArguments().getSerializable(QuestionsActivity.QUESTIONS) != null) {
            this.questions = (QuestionsBean) getArguments().getSerializable(QuestionsActivity.QUESTIONS);
        } else {
            this.questions = questions;
        }
    }

}

I'm really stuck for many hours now ... Any help is really appreciated :)

Answer 1

First, since you're making use of the fragment's Argument bundle to store your data, make sure it is properly serializable - check if the embedded questions.getQuestionList() isn't null or something.

If you're going for a new fragment each time you click on a listItem, you might as well store the argument beans directly as a property of your fragment, at least as a temporary measure until you find what's wrong.

public static QuestionsFragment newInstance(QuestionsBean questions) {
    QuestionsFragment questionFragment = new QuestionsFragment();
    questionFragment.questions = questions;
    return questionFragment;
}

Second, try to harmonize the refresh code in your fragment's onResume() and the refresh code in your fragment's refresh(), maybe have onResume call refresh(). Also make sure that your refresh() code updates your Adapter so you can actually display any of the new values. If you let go of using the Argument Bundle (at least until you find your bug), the code becomes much simpler.

@Override
public void onResume() {
    super.onResume();
    refresh(this.questions);
}

public void refresh(QuestionsBean questions) {
    this.questions = questions;
    adapter.setQuestions(questions);
}

and the last step is your activity code - try to remove all code that mention the QuestionsFragment outside of your displayFragment method. Simply call displayFragment from your activity's onResume(), and from the listItemClick events.

With that kind of code, a new QuestionFragment will be allocated once by the LayoutInflater of the activity's onCreate, then replaced with the default category questions during onResume, then replaced after each click with the selected category. You can then track more easily what's really happening and maybe start building up from there?

From that point on I would personally adjust the displayFragment method to check if the QuestionFragment exists and then just refresh it instead of replacing it with a new one.

Good luck, tell us how it goes!

Answer 2

I would guess that it's because you are returning a fragment, not a view when you use the newInstance method, and doing a FragmentTransaction is about changing views.

Here's how I would do this...

To call the right hand fragment, I would change your onItemClick to this:

public void onItemClick(AdapterView<?> parent, View view, int position, long id) {        
    QuestionsFragment fragment = new QuestionsFragment(((QuestionsBean)QuestionsGroupListView.getItemAtPosition(position));
    getFragmentManager().beginTransaction().replace(R.id.fragmentQuestions, fragment).commit();
}

Then I'd change the QuestionsFragment.

Remove the newInstance method and insert a constructor with the code that was in the newInstance:

public QuestionsFragment(QuestionBean questions){
    // Supply index input as an argument.            
    Bundle args = new Bundle();            
    args.putSerializable(QuestionsActivity.QUESTIONS, questions);            
    questionFragment.setArguments(args);     
}

That way when you call for the new fragment it will take your parameters and continue on to create the view and then return that, which is what you need.

Hope this helps!