java.lang.NullPointerException : displaying records from database in an expandable listview

Question

As the question dictates, i need to display records from database, different record for each child.ie, child 1= record 1 data. child 2 =record 2 data.so and so. i came up with t

Answer 1

It should be like below. Also post the stack trace so that we can help you further

public class DisplayActivity extends ListActivity {
DBAdapter db;
@Override
public void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_display_cursor); 
 db=new DBAdapter(this);  
Button viewbutton=(Button)findViewById(R.id.button2);
viewbutton.setOnClickListener(new OnClickListener()
{
       @override
       public void onClick(View v)
       {
             // do something
       }   

});
}

Edit:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

  <ListView 
android:layout_height="wrap_content" 
android:layout_above="@+id/button1"
android:layout_width="fill_parent" 
android:id="@+id/lv" />

  <Button
      android:id="@+id/button1"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_alignParentBottom="true"
      android:layout_centerHorizontal="true"
      android:text="Button" />

</RelativeLayout>

MainActivity.java

public class MainActivity extends Activity {

    ListView lv;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button b = (Button) findViewById(R.id.button1);
        lv= (ListView) findViewById(R.id.lv);
        b.setOnClickListener(new OnClickListener()
        {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                // set your adapter to listview here
            }

        });
    }
}