Android Null Pointer Exception when Creating Database

Question

I have a sample app which creates a database, table and inserts a row of values.

Here is my MainActivity.java:

public class MainActivity extends Activity {

protected static final android.content.Context Context = null;
public String ReadingMode="";

@Override
protected void onCreate(Bundle savedInstanceState) {


             SQLiteDatabase sampleDB =  Context.openOrCreateDatabase("WaterElectricityReading", MODE_WORLD_READABLE, null);

             sampleDB.execSQL("CREATE TABLE IF NOT EXISTS " +
                        "SampleTable " +
                        " (LastName VARCHAR, FirstName VARCHAR," +
                        " Country VARCHAR, Age INT(3));");

             sampleDB.execSQL("INSERT INTO " +
                        "SampleTable " +
                        " Values ('Makam','sample','India',25);");

             sampleDB.close();                       
        }


@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.activity_main, menu);
    return true;
}

}

When I debug line by line, Null pointer exception is raised near the line:

 SQLiteDatabase sampleDB =  Context.openOrCreateDatabase("WaterElectricityReading", MODE_WORLD_READABLE, null);

I see that sampleDB is null and Database is not being created.

Is any thing wrong with my code?

Arash GM · Accepted Answer · 2013-03-05 11:12:17Z

3

you are initializing your Context with null

protected static final android.content.Context Context = null;

so when you are using your null Context , it will throw an NPE, you can Set your Context with your Activity Context and then use your Context

Context = MainActivity.this;

or just use this

SQLiteDatabase sampleDB =  this.openOrCreateDatabase("WaterElectricityReading", MODE_WORLD_READABLE, null);

edited Mar 5, 2013 at 11:12

answered Mar 5, 2013 at 11:06

Arash GM

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Comments

AnujMathur_07 · Accepted Answer · 2013-03-05 11:07:24Z

1

You are initializing as protected static final android.content.Context Context = null; and then using it as Context.openOrCreateDatabase("WaterElectricityReading", MODE_WORLD_READABLE, null);

It will produce null pointer exception for obvious.

answered Mar 5, 2013 at 11:07

AnujMathur_07

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Paul Lammertsma · Accepted Answer · 2013-03-05 11:21:48Z

1

Repalce

  SQLiteDatabase sampleDB =  Context.openOrCreateDatabase("WaterElectricityReading", MODE_WORLD_READABLE, null);

with

  SQLiteDatabase sampleDB =  this.openOrCreateDatabase("WaterElectricityReading", MODE_WORLD_READABLE, null);

Reason :

Activity is subclass of Context so you can use this.
openOrCreateDatabase is not a static method so you cannot call it using class name.

edited Mar 5, 2013 at 11:21

Paul Lammertsma

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answered Mar 5, 2013 at 11:10

Mr Coder

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