Question

cantmano is the index, it starts on 0. Another method increases with cant++.
I recheck that 0 <= cantmano <= 10

public void dibujar(){
    //actualiza la pantalla
    if (cantmano >= 0 && cantmano < 10 && cantcroupier >= 0 && cantcroupier < 10){
        TextView textomano = (TextView)findViewById(R.id.textView3);
        TextView textocroupier = (TextView)findViewById(R.id.textView5);
        CharSequence buffer = textomano.getText();

        textomano.setText( buffer + " " +
            String.valueOf(manojugador[cantmano].getPalo())+ " de " +
            String.valueOf(manojugador[cantmano].getNumero()) ); // <-- ERROR

        textocroupier.setText( String.valueOf(cantmano) );
    }
}

I get a nice

Caused by: java.lang.NullPointerException
    at com.pruebas.blackjack.blackjack.dibujar(blackjack.java:58)
    at com.pruebas.blackjack.blackjack.onCreate(blackjack.java:23)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2717)

EDITS:
.getNumero() returns the int with the value of a requested CARD. (playing card type)
.getPalo() returns an int where 1= diamonds, etc.

initialization of manojugador:

Carta manojugador[]= new Carta[10];

constructor of Carta:

public Carta(){
    int palo=0;
    int numero=0;
}

MIDNIGHT UPDATE:
With some improvements i managed it to get over the error. BUT now the array has all 0 values when written. This has to be an easy to solve but that’s the final step before accepting the best answer.

Here’s the method that adds cards:

public void hit(View v){
        //sacan cartas
        if (cantmano < manojugador.length){
        manojugador[cantmano]=mazo.darcarta(); //adds a random Card to the manojugador. mazo means deck.
        manocroupier[cantcroupier]=mazo.darcarta(); //adds a random Card to the manojugador. mazo means deck.
        cantmano++;
        cantcroupier++;
        }
        dibujar();
    }

Answer 1

Your manojugador array null elements and your cantmano is somehow pointing to one of those null elements.

For instance, let’s say you have:

ManoJugador [] cantmano = new ManoJugador[10];

cantmano[0] = new ManoJugador();
cantmano[1] = new ManoJugador();
cantmano[2] = new ManoJugador();

You array beyond index 3 you have nulls. That’s why when your try to get the numero of null you get NullPointerException.

EDIT

As per your edit:

Yeap, definitely, you have a null value there. Debug that part and you’ll see some null values

hint: System.out.println( java.util.Arrays.toString( someArray ));

Suerte!