Android适配器getView null

Question

When it starts run , there is no error in first 5 row and follower 3 row. But then it gives null pointer exception. I can't solve why it is happening ?

Code snippet:

public View getView(int position, View convertView, ViewGroup viewGroup) {
    PaylasilanHolder holder;
    final int pozisyon = position;
    Object currentpaylasilan = getItem(position);
    Paylasilanlar paylasilan = (Paylasilanlar) currentpaylasilan;
    if (convertView == null) {
        Log.i("tago", "convertview null");
        holder = new PaylasilanHolder();
        if (paylasilan.cesit.equals("text")) {

            convertView = lala.inflate(R.layout.paylasilanyazi,null);
            holder.tv1 = (TextView) convertView.findViewById(R.id.textView11);
            holder.tv2 = (TextView) convertView.findViewById(R.id.textView12);
            holder.tv3 = (TextView) convertView.findViewById(R.id.textView13);
            holder.image1 = (ImageButton) convertView.findViewById(R.id.imageButton11);
            Log.i("tago", "texttexttext");
        } else if (paylasilan.cesit.equals("teklifoto")) {

            convertView = lala.inflate(R.layout.paylasilanresim,null);
            holder.tv1 = (TextView) convertView.findViewById(R.id.textView11);
            holder.tv2 = (TextView) convertView.findViewById(R.id.textView12);
            holder.tv3 = (TextView) convertView.findViewById(R.id.textView13);
            holder.image1 = (ImageButton) convertView.findViewById(R.id.imageButton11);
            Log.i("tago", "tekliteklitekli");
        } else if (paylasilan.cesit.equals("ikilifoto")) {
            Log.i("tago", "ikiliikiliikili");
        } else if (paylasilan.cesit.equals("anket")) {

            convertView = lala.inflate(R.layout.paylasilananket, null);
            holder.etv1 = (EditText) convertView.findViewById(R.id.editText5);
            holder.etv2 = (EditText) convertView.findViewById(R.id.editText6);
            holder.etv3 = (EditText) convertView.findViewById(R.id.editText7);
            holder.etv4 = (EditText) convertView.findViewById(R.id.editText8);
            Log.i("tago", "anketanketanket");
        }

        convertView.setTag(holder);

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

    if (paylasilan.cesit.equals("text")) {
        holder.tv1.setText(paylasilanlarListesi.get(position).getGonderenid());
        holder.tv2.setText(paylasilanlarListesi.get(position).getYaziveyaurl());
    } else if (paylasilan.cesit.equals("teklifoto")) {
        holder.tv3.setText(paylasilanlarListesi.get(position).getGonderenid());
        new urldenResim(holder.image1).execute(paylasilanlarListesi.get(position).getYaziveyaurl());
    } else if (paylasilan.cesit.equals("ikilifoto")) {

    } else if (paylasilan.cesit.equals("anket")) {
        holder.etv1.setText(paylasilanlarListesi.get(position).getQuestion());
        holder.etv2.setText(paylasilanlarListesi.get(position).getOption1());
        holder.etv3.setText(paylasilanlarListesi.get(position).getOption2());
        holder.etv4.setText(paylasilanlarListesi.get(position).getOption3());
    }
    return convertView;
}

It gives :

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference    

 com.example.bahadir.myapplicationn.PaylasilanlarAdapter.getView(PaylasilanlarAdapter.java:128)

in holder.tv3.settext() method.

How can i overcome it ?

Answer 1

You can't mix different views like that. Because if for example you have first 10 items paylasilan.cesit.equals("anj=ket") and after that some other items, adapter views would be already initialized with R.layout.paylasilananket and sure that holder.tv3.setText would give you NullPointerException

You should either mix all layouts into one layout and show/hide parts according to item which is pretty bad or use viewTypes like in this tutorial: http://www.survivingwithandroid.com/2014/08/android-listview-with-multiple-row.html

Answer 2

Since you're using only one kind of a view holder I would think, that you're also handling one kind of view in your adapter. So you're creating a view of one type and reuse it with another.

You have to override getViewTypeCount() and getItemViewType(int position) to return the correct values for your model to work.

Answer 3

You can't do this as you're doing now. The crash arises when you try to reuse a cell which is of a different kind, and you're trying to get a reference to a non-existance text-field.

You have to add another field to "PaylasilanHolder" and set that to the type of cell when you inflate a new cell.

When you are reusing a cell ie: when "convertView != null", you also have to check whether the cell types are the same by referring to the new field you defined in "PaylasilanHolder". Otherwise, inflate the cell again.