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Answer 1

A:

It looks like the error is on line 53, not 54.

In any case, you're dereferencing a null pointer. Just check and see which variable isn't defined, and avoid calling it (or make sure it's properly initialized).

Assuming you've listed the correct line, it's either txtArrival or Booking.this (I'm not sure if you can you call this on a class.).

Trevor Johns 2010-08-06 03:09:47

Sorry, what do you mean by dereferencing a null pointer and how would i go about doing it?

User358218 2010-08-06 03:20:12

You call Booking.this from an inner class of Booking to refer to the Booking object instead of the inner one.

Carl Manaster 2010-08-06 03:21:21

So instead of Booking.this, i would change it to?

User358218 2010-08-06 03:23:48

Every variable in Java is a reference to an object (or a primitive, but I digress). If you call myObj.foo(), Java first looks up what object myObj points to. If you say "myObj=null" first, then calling myObj.foo() is guaranteed to fail. That's what dereferencing a null pointer is.

Trevor Johns 2010-08-06 03:33:30

But i did not declare any myobj = null in my codes?

User358218 2010-08-06 03:47:55

Answer 2

A:

I believe you need to make sure that the variable "C" is not null.

String title=c.getString(1); txtArrival.setText(title);

seems to be the trouble code, and if c is null, then c.getString(1) should return nullpointerexception, or it might just return nothing, causing title to be null, and setting txtarrival.setText with a null should throw an error too.

Nicholas 2010-08-06 04:09:54

So would i go about solving it? As i already have c = db.getSpinnerData(), which has data in the cursor.

User358218 2010-08-06 04:11:37

Add an if there that checks if either c is null, or title.

Nicholas 2010-08-06 05:08:54

Answer 3

A:

There is only one place on line 53 where you can get NPR: txtArrival.setText().

I believe you forgot to set TextView's ID to R.id.txtArrival in layout and (TextView) findViewById(R.id.txtArrival); returns NULL.

nunthrey 2010-08-06 04:39:39

I already did TextView txtArrival = (TextView) findViewById(R.id.txtArrival); in my oncreate method.

User358218 2010-08-06 05:29:09

Answer 4

+2 A:

You are creating local variables with the same names as your class members. This leads to the members being hidden by the local ones which is why you are getting NullPointerExceptions. You are simply not giving the members any value which is why they are null.

What you want to do is:

package one.two;

import android.app.Activity;
import android.database.Cursor;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.SimpleCursorAdapter;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.AdapterView.OnItemSelectedListener;


public class Booking extends Activity
{
    private DBAdapter db; 
    private Spinner colourSpinner;
    public Cursor c;
    public TextView txtArrival;

    /** Called when the activity is first created. */
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        db = new DBAdapter(this);
        this.setContentView(R.layout.booking);
        txtArrival = (TextView) findViewById(R.id.txtArrival); // Member assignment
        colourSpinner = (Spinner) findViewById(R.id.myspinner); // Member assignment
        db.open();
        fillData();
        db.close();
        colourSpinner.setOnItemSelectedListener(new MyOnItemSelectedListener());
    }

    private void fillData()
    {
        c = db.getSpinnerData();
        startManagingCursor(c);
        String[] from = new String[]{DBAdapter.KEY_ARRIVAL};
        int[] to = new int[]{android.R.id.text1};
        SimpleCursorAdapter adapter =
        new SimpleCursorAdapter(this,R.layout.booking, c, from, to );
        adapter.setDropDownViewResource( android.R.layout.simple_spinner_dropdown_item );
        // Removed this line, since members is set in onCreate
        colourSpinner.setAdapter(adapter);
    }
    public class MyOnItemSelectedListener implements OnItemSelectedListener
    {
        public void onItemSelected(AdapterView<?> arg0, View v,int position, long id)
        {
            boolean result = Booking.this.c.moveToPosition(position);
            if (result) {
                String title=Booking.this.c.getString(1);
                Booking.this.txtArrival.setText(title);
            }

        }
        @Override
        public void onNothingSelected(AdapterView<?> arg0)
        {
            // TODO Auto-generated method stub

        }
    };
}

Key 2010-08-06 07:04:37

There is still a null error stated, in my logcat

User358218 2010-08-10 03:14:42

The error is at Booking.this.txtArrival.setText(title);

User358218 2010-08-10 03:22:47

Have you used the code in my version of onCreate? I have moved line 7 and 8 of onCreate and removed the local variable creation. Make sure you understand why you had the null pointer from the beginning and you will be able to solve these issues much faster!

Key 2010-08-10 07:19:04

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