Question

Possible Duplicate:
LogCat entry meaning 2

LogCat say that the problem is with the Array Adapter that it has a NullPointerException. How can I solve this problem? The application crashes if I press the button add.

package com.example.to_doliste;

import java.util.List;
import android.app.ListActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.EditText;

public class MainActivity extends ListActivity {
    private CommentsDataSource datasource;

      @Override
      public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        datasource = new CommentsDataSource(this);
        datasource.open();

        List<Comment> values = datasource.getAllComments();

Array Adapter get build

        ArrayAdapter<Comment> adapter = new ArrayAdapter<Comment>(this,
            android.R.layout.simple_list_item_1, values);
        setListAdapter(adapter);
      }

it is used here

      public void onClick(View view) {
        @SuppressWarnings("unchecked")
        ArrayAdapter<Comment> adapter = (ArrayAdapter<Comment>) getListAdapter();
        Comment comment = null;
        switch (view.getId()) {
        case R.id.add:

          String comments;
            EditText Feld1 = (EditText)findViewById(R.id.editText1);

            if (Feld1.getText().toString().length() == 0)
                    {
                return;
                    }

            comments = (Feld1.getText().toString());

            Feld1.setText(String.valueOf(comments));


          adapter.add(comment);
          break;
        case R.id.delete:
          if (getListAdapter().getCount() > 0) {
            comment = (Comment) getListAdapter().getItem(0);
            datasource.deleteComment(comment);
            adapter.remove(comment);
          }
          break;
        }
        adapter.notifyDataSetChanged();
      }

here the adapter stops

      @Override
      protected void onResume() {
        datasource.open();
        super.onResume();
      }

      @Override
      protected void onPause() {
        datasource.close();
        super.onPause();
      }

    } 

Answer 1

Here

Comment comment = null;

You are trying to add comment to adapter but comment is null. You are not updating any new value in comment after initializing it to null, so update it before adding or removing it from adapter.