java - The content of EditText contained into a Android ListView isn't saved

Question

On my project I have to show to the user a ListView which is contained basically of EditText.

It is like a questionnaire, when he answer to the question he can go down and answer to the next question. (and go back)

public class onAdapter extends BaseAdapter {
    List<PointVerification> mObjects;
    Context mContext;
    LayoutInflater mInflater;

    HashMap<Integer, List<ChoixPointVerification>> mChoix;
    HashMap<Integer, ReponsePointVerification> mReponses;
    HashMap<Integer, String> mReponsesActuel;
    Integer mPositionSelectionne;
    Integer mIdIntervention;


    /**
     * Constructeur
     * @param context

     * @param listePointsVerification Liste des points de vérification à afficher.
     * @param listeChoixPointsVerification liste des choix de points de vérification pour chaque point de vérification.
     * @param listeReponsesPointsVerification réponses déjà fournies pour chaque point de vérification
     * @param idIntervention Identifiant de l'intervention
     */
    public onAdapter(
            Context context,

            Integer idIntervention, 
            List<PointVerification> listePointsVerification,
            List<ChoixPointVerification>> listeChoixPointsVerification,
            ReponsePointVerification> listeReponsesPointsVerification) {

        this.mInflater = LayoutInflater.from(context);
        this.mContext = context;
        this.mObjects = listePointsVerification;

        this.mChoix = listeChoixPointsVerification;
        this.mReponses = listeReponsesPointsVerification;
        this.mIdIntervention = idIntervention;


        // préparation des réponses par position
        this.mReponsesActuel = new HashMap<Integer, String>();
    }


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

        final Integer idPointVerification = getItem(position).id;

        if (convertView == null)
        {
            row = mInflater.inflate(R.layout.intervention_reponses_controle_nombre, null);

            EditText edValeur = (EditText) row.findViewById(R.id.edValeur);
            // Ajout de l'évènement lorsque l'on change la valeur
            // evènement d'enregistrement
            edValeur.addTextChangedListener(new TextWatcher() 

                @Override
                public void onTextChanged(CharSequence s, int start, int before, int count) {
                }

                @Override
                public void beforeTextChanged(CharSequence s, int start, int count,
                        int after) {
                }

                @Override
                public void afterTextChanged(Editable s) {
                    // This hashmap is a try workaround to the bug
                    // i register all modifications into this hashmap
                    mReponsesActuel.put(
                            idPointVerification,
                            s.toString());

                    // SAVE PROCEDURE
                    // REMOVED FOR THE EXAMPLE
                    // BUT I UPDATE MY DATABASE
                }
            });
        }
        else
        {
            row = convertView;
        }

        EditText edValeur = (EditText) row.findViewById(R.id.edValeur);

        // update of the text
        // it is the contained in the hashmap
        if (mReponsesActuel.containsKey(idPointVerification)) {
            String valeur = mReponsesActuel.get(idPointVerification);
            edValeur.setText(valeur);
        // otherwhise i will look into the database
        } else if (mReponses != null && mReponses.containsKey(idPointVerification)
                && mReponses.get(idPointVerification).valeur != null) {
            edValeur.setText(mReponses.get(idPointVerification).valeur);
        }
        else
        {
            edValeur.setText("");
        }

        return row;
    }
}

I don't know why but the user go down in the ListView, the content is unsaved and show some special values like others EditText. I didn't find how to correct that behaviour and it's really in a hurry.

Basically I made a TextWatcher which register data into the database and also into a temporary HashMap which contains all values. That data is called back when GetView is called. If I remove that initialisation, the EditText is erased.

Note : I made some test in my code so there may be different problem.

Edit

I uploaded a project with the problem : http://dl.free.fr/rbqOhUfJF

Here the steps to reproduce the problem :

1. launch the project in debug mode

2. write in the first row A, in the second B, in the third C

3. Scroll down until C is hidden

4. scroll up to the top. Result : There is no more text.

If you look closely on the debug log you can see line with afterText. Each times we write some text in the part 2, there will be a debug line with the registration of the event.

But at the phase 3, when you hide an item. the event will be launched with ""

Result : in the 4th phase, it loads the "" string

Answer 1

To speed up things in most mobile apps (Android iOS ...) cells of lists are usually recycled. This spares memory especially for long lists. Therefore you have to get the data of a new displayed cell. When the cell goes outside the screen, its layout/view is destroyed. In your case you have to save the text of the edit text somewhere. That's what you are trying to do with the hashmap.

I don't see any particular mistake in your code.

If the question is about the "workaround" of using the hashmap, I confirm that for me it is up to you to save the states of the edit text. Using a hashmap is one way of doing it.

By the way getItem(position).id can be replaced by getItemId(position) which is here for that purpose.

Not sure if all this answers your question.

EDIT

Now that I understood your question correctly I can provide some code. I must say that I am not fully happy with the solution found but at least it is working.

The problem with the TextWatcher is that you have no access to the context and of the corresponding view.

Using setOnFocusChangeListener solved the problem. So here is the code I finally got working.

public final class PointVerificationAdapter extends BaseAdapter {
    List<BasicNameValuePair> mObjects;
    Context mContext;
    LayoutInflater mInflater;
    HashMap<Integer, String> mReponsesActuel;
    ArrayList<String> myItems = new ArrayList<String>();

    public PointVerificationAdapter(
            Context context,
            List<BasicNameValuePair> listObjets
            ) {

        this.mInflater = LayoutInflater.from(context);
        this.mContext = context;
        this.mObjects = listObjets;

        for (int i = 0; i < 30; i++) {
            myItems.add(Integer.toString(i));
        }
    }

    @Override
    public int getCount() {
        return mObjects.size();
    }

    @Override
    public BasicNameValuePair getItem(int position) {
        return mObjects.get(position);
    }

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

    static class ViewHolder {
        EditText yourEditText;
    }

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

        ViewHolder holder = null;

        if (convertView == null)
        {
            holder = new ViewHolder();
            convertView = mInflater.inflate(R.layout.intervention_reponses_controle_nombre, parent, false);
            convertView.setId(position);
            holder.yourEditText = (EditText) convertView.findViewById(R.id.edValeur);

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

        ((TextView) convertView.findViewById(R.id.tvNom)).setText(Integer.toString(position));

        holder.yourEditText.setText(myItems.get(position));
        holder.yourEditText.setId(position);
        holder.yourEditText.setOnFocusChangeListener(new OnFocusChangeListener() {
            public void onFocusChange(View view, boolean hasFocus) {
                if (!hasFocus){
                    final int position = view.getId();
                    final EditText editText = (EditText) view;
                    myItems.set(position, editText.getText().toString());
                }
            }
        });

        return convertView;
    }

}

FINAL EDIT

The previous code is working but I wasn't happy with it because you asked for addTextChangedListenerand not for onFocusChange.

So here is the solution :

public final class PointVerificationAdapter extends BaseAdapter {
    List<BasicNameValuePair> mObjects;
    Context mContext;
    LayoutInflater mInflater;
    HashMap<Integer, String> mReponsesActuel;
    ArrayList<String> myItems = new ArrayList<String>();

    public PointVerificationAdapter(
            Context context,
            List<BasicNameValuePair> listObjets
            ) {

        this.mInflater = LayoutInflater.from(context);
        this.mContext = context;
        this.mObjects = listObjets;

        for (int i = 0; i < 30; i++) {
            myItems.add(Integer.toString(i));
        }
    }

    @Override
    public int getCount() {
        return mObjects.size();
    }

    @Override
    public BasicNameValuePair getItem(int position) {
        return mObjects.get(position);
    }

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

    static class ViewHolder {
        EditText yourEditText;
    }

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

        ViewHolder holder = null;

        if (convertView == null)
        {
            holder = new ViewHolder();
            convertView = mInflater.inflate(R.layout.intervention_reponses_controle_nombre, parent, false);
            convertView.setId(position);
            holder.yourEditText = (EditText) convertView.findViewById(R.id.edValeur);
            holder.yourEditText.setId(position);
            holder.yourEditText.addTextChangedListener(new GenericTextWatcher(holder.yourEditText));
            convertView.setTag(holder);
        }
        else
        {
            holder = (ViewHolder) convertView.getTag();
            holder.yourEditText.setId(position);
        }

        ((TextView) convertView.findViewById(R.id.tvNom)).setText(Integer.toString(position));

        holder.yourEditText.setText(myItems.get(position));

        return convertView;
    }

    private class GenericTextWatcher implements TextWatcher{

        private View view;
        private GenericTextWatcher(View view) {
            this.view = view;
        }

        public void beforeTextChanged(CharSequence charSequence, int i, int i1, int i2) {}
        public void onTextChanged(CharSequence charSequence, int i, int i1, int i2) {}

        public void afterTextChanged(Editable editable) {
            final int position = view.getId();
            final EditText editText = (EditText) view;
            myItems.set(position, editText.getText().toString());
        }
    }
}