Check if Registration Exists in BD Sqlite and if there is no Return Message

Question

Good night,

I’m trying to make a little app that consists of searching a Sqlite database. For the research I will use two forms, ie through the UN Number and through the Name.

However I am facing a problem, the app bursts in case you try to search for any registration that does not exist.

How can I trigger an error message in case the search does not find a result?

Dbhelper:

//Metodo ONU Query
public List<Elemento> getONU()
{
    List<Elemento> listaElementos = new ArrayList<Elemento>();

    //Seleccionar Query
    String selectQuery = "SELECT *FROM " + TABLE_NAME + " WHERE ONU = " + MainActivity.editText_ONU_search.getText();
    dbase = this.getReadableDatabase();

    Cursor cursor = dbase.rawQuery(selectQuery, null);

    //Loop por todas as linhas da BD e adiciona-las a lista
    if(cursor.moveToFirst())
    {
            Elemento element = new Elemento();
            element.setID(cursor.getInt(0));
            element.setONU(cursor.getInt(1));
            element.setNOME_SUB(cursor.getString(2));
            listaElementos.add(element);

    }

    //Return listaElementos;
    return listaElementos;

}

//Metodo Nome Query
public List<Elemento> getNomeSubstancia()
{
    List<Elemento> listaElementos = new ArrayList<Elemento>();

    //Seleccionar Query
    String selectQuery = "SELECT * FROM " + TABLE_NAME + " WHERE NOME_SUB = '" + MainActivity.editText_NOME_search.getText() + "'";
    dbase = this.getReadableDatabase();

    Cursor cursor = dbase.rawQuery(selectQuery, null);

    //Loop por todas as linhas da BD e adiciona-las a lista
    if(cursor.moveToFirst())
    {
            Elemento element = new Elemento();
            element.setID(cursor.getInt(0));
            element.setONU(cursor.getInt(1));
            element.setNOME_SUB(cursor.getString(2));
            listaElementos.add(element);

    }

    //Return listaElementos;
    return listaElementos;

}

Onuresultactivity:

public class OnuResultActivity extends AppCompatActivity {

//Declaração de variaveis
List<Elemento> listaElementos;
int elemento_id = 0;

Elemento currentElemento;
TextView textView_onu, textView_nome_sub;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_onu_result);

    DbHelper db = new DbHelper(this);
    listaElementos = db.getONU();
    currentElemento = listaElementos.get(elemento_id);

    textView_onu = (TextView)findViewById(R.id.textView_onu);
    textView_nome_sub = (TextView) findViewById(R.id.textView_nome_sub);

    //Apresentar Info
    setElementosView();

}

private void setElementosView() {

    textView_onu.setText(Integer.toString(currentElemento.getONU()));
    textView_nome_sub.setText(String.valueOf(currentElemento.getNOME_SUB()));


    elemento_id++;
}

}

Nomeresultactivity:

public class NomeResultActivity extends AppCompatActivity {

    //Declaração de variaveis
    List<Elemento> listaElementos;
    int elemento_id = 0;

    Elemento currentElemento;
    TextView textView_onu, textView_nome_sub;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_nome_result);

        DbHelper db = new DbHelper(this);
        listaElementos = db.getNomeSubstancia();
        currentElemento = listaElementos.get(elemento_id);

        textView_onu = (TextView)findViewById(R.id.textView_onu);
        textView_nome_sub = (TextView) findViewById(R.id.textView_nome_sub);

        //Apresentar Info
        setElementosView();
    }

    private void setElementosView() {

        textView_onu.setText(Integer.toString(currentElemento.getONU()));
        textView_nome_sub.setText(String.valueOf(currentElemento.getNOME_SUB()));

        elemento_id++;
    }
}

Any idea how I can return a warning message when the search is not found in order to cover the possibility that the search entered by the user is not matching what is in the BD.

Regards

Answer 1

The way I do this type of task and the next, right after the query I make a comparison to see if the query returned any result, then I take my Cursor and check it, if(cursor.getCount() == 0){ message }So if you don’t have any records in the bank you’ll return 0 lines, out of curiosity where you’re from? good luck in school

Answer 2

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_onu_result);

DbHelper db = new DbHelper(this);
listaElementos = db.getONU();

if(listaElementos.size() > 0){
   currentElemento = listaElementos.get(elemento_id);
}else{
  //AQUI VOCÊ PODE USAR UM TOAST OU UM DIALGO PRA EXIBIR A 
  //MENSAGEM QUE QUISER
}
textView_onu = (TextView)findViewById(R.id.textView_onu);
textView_nome_sub = (TextView) findViewById(R.id.textView_nome_sub);

//Apresentar Info
setElementosView();

}

I guess that’s what I understood from your question.