Alertdialog ANDROID accent error

Question

I’m having problems with the AlertDialog, when opened it exhibits the accents and neither cedilla, in the place appears that old "triangle with interrogation in". What to do to solve?

public void alertaInternet(){
    AlertDialog.Builder alertDialog = new AlertDialog.Builder(mContext);

    // Definindo Dialog Title
    alertDialog.setTitle("Sem conexão a internet!");

    // Definindo Dialog Message
    alertDialog.setMessage("O aplicativo precisa de conexão a internet para prosseguir.");

    // Ao pressionar o botão OK
    alertDialog.setNegativeButton("Fechar", new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface dialog, int which) {
            dialog.cancel();
        }
    });

    // Mostrando Alert Message
    alertDialog.show();
}