Android: erro NullPointerException on getWritableDatabase()

Question

I have a problem NullPointerException on getWritableDatabase()

Database

I am trying to build a small application that store some information in a SQLite table. But I always receive a "Java.lang.NullPointerException" exception in getWritableDatabase method. Can anyone help me? All the code is below.

public class PacienteDatabase extends SQLiteOpenHelper {

private static final String DB_NAME = "paciente.sqlite";
private static final int VERSION = 1;
private static final String TABLE = "paciente";


public PacienteDatabase(Context context) {
    super(context, DB_NAME, null, VERSION);
}

@Override
public void onCreate(SQLiteDatabase db) {
    // Crear tabla paciente
    db.execSQL("create table paciente (" +
            "_id integer primary key autoincrement, start_date integer)");
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

}

}

Activiy

public class RegistroPaciente extends ActionBarActivity {

private Button mBotonOk;

private PacienteDatabase mPaciente;
private Context c;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_registro_paciente);
    mPaciente = new PacienteDatabase(c);

    mBotonOk = (Button)findViewById(R.id.boton_registro_ok);


    mBotonOk.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            ContentValues datos = new ContentValues();

            datos.put("start_date", 1000 );

            mPaciente.getWritableDatabase().insert("paciente", null, datos);

            finish();
        }
    });
}

Error in log cat

03-16 22:22:46.531    1181-1181/com.example.franciscodelgadogarcia.projecto E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.franciscodelgadogarcia.projecto, PID: 1181
java.lang.NullPointerException
        at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:224)
        at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:164)
        at com.example.franciscodelgadogarcia.projecto.RegistroPaciente$1.onClick(RegistroPaciente.java:84)
        at android.view.View.performClick(View.java:4438)
        at android.view.View$PerformClick.run(View.java:18422)
        at android.os.Handler.handleCallback(Handler.java:733)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:136)
        at android.app.ActivityThread.main(ActivityThread.java:5017)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
        at dalvik.system.NativeStart.main(Native Method)

Answer 1

c object of Context is null initialize it before passing cto PacienteDatabase class constructor :

 c=RegistroPaciente.this
 mPaciente = new PacienteDatabase(c);