Android-Java：Arraylists似乎是空的

Question

我知道这是一个愚蠢的错误，这是一个新手的错误，但我无法解决。问题是arraylists的值似乎是空的onCreate在按钮的onclick下面。但是当我点击按钮我看到他们的价值观在调试器上。如何在不使用onclick或其他东西的情况下使用它们？我需要帮助。

  ArrayList<String> menkulList = new ArrayList<>();
ArrayList<String> miktarList = new ArrayList<>();
ArrayList<String> fiyatList = new ArrayList<>();
ArrayList<Double> tutarList = new ArrayList<>();
private TextView tx;
Button btn;
TableLayout table;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.portfoy);
    table = (TableLayout) findViewById(R.id.customer_table);
    btn = (Button) findViewById(R.id.tikla);
    btn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            for(String s : menkulList) {
                Log.i("Menkul list", s);
            }
            for(String s : miktarList) {
                Log.i("Miktar list", s);
            }
            for(String s: fiyatList) {
                Log.i("Fiyat list", s);
            }
            for(Double d: tutarList) {
                Log.i("Tutar list", d.toString());
            }
        }
    });
    String jsonUrl = createJsonUrl();
    jsonProcess(jsonUrl);
    for(String s : menkulList) {
        Log.i("Menkul list", s);
    }
    for(String s : miktarList) {
        Log.i("Miktar list", s);
    }
    for(String s: fiyatList) {
        Log.i("Fiyat list", s);
    }
    for(Double d: tutarList) {
        Log.i("Tutar list", d.toString());
    }

}
public void jsonProcess(String jsonString){
    RequestQueue queue = Volley.newRequestQueue(this);
    String url = jsonString;

    // Request a string response from the provided URL.
    StringRequest stringRequest = new StringRequest(Request.Method.GET, url,
            new Response.Listener<String>() {
                @Override
                public void onResponse(String response) {
                    // Display the first 500 characters of the response string.
                    try {
                        JSONObject jObj = new JSONObject(response);
                        JSONArray jArr = jObj.getJSONArray("Item");
                        for (int i = 0; i < jArr.length(); i++) {
                            jObj = jArr.getJSONObject(i);
                            String s1 = jObj.getString("Symbol");
                            String s2 = jObj.getString("Qty_T2");
                            String s3 = jObj.getString("LastPx");
                            Double tutar = Double.parseDouble(s2) * Double.parseDouble(s3);
                            fillArrayLists(s1,s2,s3,tutar);
                        }
                    }catch(Exception e){
                        Log.i("Error while json parse",e.toString());
                    }
                }
            }, new Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError error) {
            Log.i("Error is",error.toString());
        }
    });
    // Add the request to the RequestQueue.
    queue.add(stringRequest);
}
public void fillArrayLists(String menkul,String miktar,String fiyat,Double tutar){

    menkulList.add(menkul);
    miktarList.add(miktar);
    fiyatList.add(fiyat);
    tutarList.add(tutar);

    fillTableLayout();
}
public void fillTableLayout(){

}
public String createJsonUrl(){
    Intent i = getIntent();
    String customerId = i.getStringExtra(MainActivity.CUSTOMER_ID);
    String jsonString = "https://tb.matriksdata.com/9999/Integration.aspx?MsgType=AN&CustomerNo=0&Username=proje&Password=proje&AccountID="+ customerId +"&ExchangeID=4&OutputType=2";
    Log.i("Json String is : ", jsonString);
    return jsonString;
}