### opdracht 4 ###

public void btnOK(View view) {

    ...

//  Herhalingen
    EditText etnHerhalingen = (EditText)findViewById(R.id.etnHerhalingen);
    int herhalingen = Integer.parseInt(etnHerhalingen.getText().toString());
    String strHerhalingen = "";

    for (int i = 0; i < herhalingen; i++) {
        strHerhalingen = strHerhalingen + i;
    }

    TextView tvHerhalingen = (TextView)findViewById((R.id.tvHerhalingen));
    tvHerhalingen.setText(strHerhalingen);
    
    ...
    
}