Android app stops when SQLiteOpenHelper is called

Question

This is my first question here in SO. So, here's my problem: I'm developing an app for android. This is how my app flows:

• I call a MainActivity;
  
• The user press a button that calls a LoginActivity;
  
• The user fill in the username and password;
  
• LoginActivity calls a AsynchronousTask that send the data for a JAX-WS (I use ksoap2 library to call my SOAP web service);
  
• If the information are right, a MenuActivity is called;
  
• There is a button for "License Plate Search". When it is pressed, I call a Activity for input the license plate and an "OK" button for search;
  
• When the "OK" button is pressed, I send the data for a new AsynchronousTask that search for the plate in my web service;
  
• If the license plate is a valid one (activity result = OK) I populate my database with: License Plate Number, Year, Model and Developer;
  
• After this I call a new Activity called ResultActivity where a show the vehicle information in a new Dialog (HERE IS THE PROBLEM);
  
• But, if the result is CANCELED (when my web service doesn't found the license plate) I just show a Alert for the user.
  

The problem is happening when I try to show the information for the user. Here is my ResultActivity:

public class ResultadoBuscaPlacaActivity extends Activity {

    private VeiculoDAO vDao;

    TextView campoPlaca;
    TextView campoModelo;
    TextView campoMarca;
    TextView campoAno;
    TextView campoRenavam;
    TextView campoProprietario;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_resultado_busca_placa);            
        campoPlaca = (TextView) findViewById(R.id.valor_placa);
        campoModelo = (TextView) findViewById(R.id.valor_modelo);
        campoMarca = (TextView) findViewById(R.id.valor_marca);
        campoAno = (TextView) findViewById(R.id.valor_ano);
        campoRenavam = (TextView) findViewById(R.id.valor_renavam);
        campoProprietario = (TextView) findViewById(R.id.valor_proprietario);    
        vDao = new VeiculoDAO(this);
        vDao.open();    

    }

    public void confirm(View v){        
        finish();
    }       

    @Override
    protected void onStart() {      
        super.onStart();
        Veiculo v = new Veiculo();
        v = vDao.getFirstElement();
        if (v.getPlaca()!=null){
            campoPlaca.setText(v.getPlaca());
            campoModelo.setText(v.getModelo());
            campoMarca.setText(v.getMarca());
            campoAno.setText(v.getAno());
            campoRenavam.setText(v.getRenavan().toString());
            campoProprietario.setText(v.getNomeProprietario());
        }           
    }

    @Override
    protected void onDestroy() {
        vDao.close();
        super.onDestroy();
    }

    @Override
    protected void onPause() {
        vDao.close();
        super.onPause();
    }    
}

The VeiculoDAO is a simple DAO that calls a Custom SQLiteOpenHelper class. The method getFirstElement() is here:

public Veiculo getFirstElement(){

        Cursor cursor = database.query(CustomSQLiteOpenHelper.TABLE_VEICULO,
                columns, null, null, null, null, null);
        cursor.moveToFirst();
        Veiculo v = new Veiculo();

        while (!cursor.isAfterLast()) {

            v.setAno(cursor.getInt(cursor.getColumnIndex(CustomSQLiteOpenHelper.COLUMN_ANO)));
            v.setMarca(cursor.getString(cursor.getColumnIndex(CustomSQLiteOpenHelper.COLUMN_MARCA)));
            v.setModelo(cursor.getString(cursor.getColumnIndex(CustomSQLiteOpenHelper.COLUMN_MOD)));
            v.setNomeProprietario(cursor.getString(cursor.getColumnIndex(CustomSQLiteOpenHelper.COLUMN_NMPROP)));
            v.setPlaca(cursor.getString(cursor.getColumnIndex(CustomSQLiteOpenHelper.COLUMN_PLACA)));
            v.setRenavan(cursor.getLong(cursor.getColumnIndex(CustomSQLiteOpenHelper.COLUMN_MARCA)));           
        }
        cursor.close();
        return v;
}

What is actually happening is: when the result activity calls the method onStart() and goes to the line:

v = vDao.getFirstElement();

The UI goes back to MenuActivity (because I called the SearchActivity by startActivityForResult() ) but it stops there, when it supposed to call ResultActivity.
In logcat, this message runs in loop:

D/dalvikvm(28637): GC_CONCURRENT freed 631K, 15% free 18650K/21824K, paused 1ms+4ms, total 25ms<br>

If I comment the specific line above, the app runs "normally" and the result Activity is called, but the information are empty (of course).

Does anyone know what should I do?

Answer 1

This loop never terminates since the cursor is never advanced inside the loop and the return value of isAfterLast() does not change.

while (!cursor.isAfterLast()) {

}

Since you are only interested in the first result, change it to

if (cursor.moveToFirst()) {

}

You can remove the earlier moveToFirst() call as redundant. It's still important to check the return value as there may be no result rows and then moveToFirst() returns false.