Question

I’m trying to create an android application which can store users location (cell tower code) with a name of his choice, i.e for example the cell tower code is 405673 and I want to store that as a ‘Home’ location.
So, essentially my program contains the following modules

1. to get users tower code.
2. to create a database.
3. to get an input string for location name from user.
4. to store these values in database.
5. to display these values when requested.

modules 1 and 2 were working perfectly individually, but when i integrate them I get a Fatal main and a null pointer exception.

My code is as below

package my.project.mil;

import android.content.Context;
import android.content.Intent;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class Cbdata extends MainActivity {

    public String str;

    public void onReceive(Context context, Intent intent) {
        //---get the CB message passed in---
        Bundle bundle = intent.getExtras();        
        SmsCbMessage[] msgs = null;
        str = "";            
        if (bundle != null)  {
            //---retrieve the SMS message received---
            Object[] pdus = (Object[]) bundle.get("pdus");
            msgs = new SmsCbMessage[pdus.length];            
            for (int i=0; i<msgs.length; i++) {
                msgs[i] = SmsCbMessage.createFromPdu((byte[])pdus[i]);                
                str += "CB " + msgs[i].getGeographicalScope() + msgs[i].getMessageCode() + msgs[i].getMessageIdentifier() + msgs[i].getUpdateNumber();                     
                str += " :";
                str += msgs[i].getMessageBody().toString();
                str += "\n";        
            }}
}

    SQLiteDatabase cd = openOrCreateDatabase("mydata", MODE_WORLD_READABLE, null);



Button submit;
Button viewdb;
EditText name;

@Override
public void onCreate(Bundle savedInstanceState)
{
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.seventh);

    viewdb = (Button) findViewById(R.id.viewdb);
    submit = (Button) findViewById(R.id.submit);
    name = (EditText) findViewById(R.id.name);

    submit.setOnClickListener(new View.OnClickListener() 
    {

        public void onClick(View arg0) {

            String locname = name.getText().toString();
            if (locname.length()>0)
            {

                cd.execSQL("CREATE TABLE IF NOT EXITSTS MLITable     (CblocationCode INT(10), CblocationName VARCHAR);");
                cd.execSQL("INSERT INTO MLITable VALUES (' ',' ');" +str +locname);
                Toast.makeText(getBaseContext(), "value successfully entered.", Toast.LENGTH_LONG).show();
            }
            else
            {
                Toast.makeText(getBaseContext(), "Please enter the location name, for example 'Home'.", Toast.LENGTH_LONG).show();
            }

        }
    });

    cd.close();

    viewdb.setOnClickListener(new View.OnClickListener() 
    {

        public void onClick(View arg0) {
            // TODO Auto-generated method stub
            // here comes the code for viewing the database


        }
    });
}



} 

My logcat is as follows

Interestingly, I’ve removed database commands to see if my code is working or not, from that I could conclude that I made a mistake in database connection line.

Now, my queries are

1. Why I’m a getting a null point exception error with my database connection and how can I resolve it?

2. I’ve used the following code to insert values into a table,

   cd.execSQL(“CREATE TABLE IF NOT EXITSTS MLITable (CblocationCode INT(10), CblocationName VARCHAR);”);
   cd.execSQL(“INSERT INTO MLITable VALUES (‘ ‘,’ ‘);” +str +locname);
   is it the correct way to pass user values to my database?

Thank you.

Answer 1

The CREATE statement has EXISTS misspelled.

The INSERT statement should read

cd.execSQL("INSERT INTO MLITable VALUES('" + str + "', '" + locname + "');");

But I think the most likely cause is that the openOrCreateDatabase call hasn’t run, so nothing is assigned to cd.