Android Button.setonclicklistener Eklediğimde Uygulama Çöküyor

LayoutInflater layoutInflater=LayoutInflater.from(this);
        View layout=layoutInflater.inflate(R.layout.dersekle,null);

        Button kaydet= (Button) findViewById(R.id.kaydet);
        Button vazgec= (Button) findViewById(R.id.vazgec);

        final Spinner spinner= (Spinner) findViewById(R.id.spinner);
        final EditText rakam= (EditText) findViewById(R.id.rakam);
        final DatePicker datePicker= (DatePicker) findViewById(R.id.datePicker);

        AlertDialog.Builder builder=new AlertDialog.Builder(this);
        builder.setTitle("Kayıt Ekle");
        builder.setView(layout);
        final AlertDialog alertDialog =builder.create();