如何等待 Volley 的响应？

Question

To summarize my problem i have a request written with Android Volley Library.

I need fill chartDataList . But there is a problem whenever i call the method it return a null array after 3 seconds it filling itself asynchronously. I want to wait for response but i dont have any idea how can i do that?

Here is my codes:

 public List<ChartData> getVolleyResponse() {
        requestQueue = Volley.newRequestQueue(getApplicationContext());
        JsonObjectRequest req = new JsonObjectRequest(
                Request.Method.GET,
                urlCreator(getCoinName()),
                null,
                response -> {
                    try {
                        JSONArray arr = response.getJSONArray("prices");
                        ChartData chartData = new ChartData();
                        for (int i = 0; i < arr.length(); i++) {
                            JSONArray jsonArray = arr.getJSONArray(i);
                            chartData.setTimeStamp(timeStampConverter(jsonArray.getString(0)));
                            chartData.setCost(jsonArray.getDouble(1));
                            chartDataList.add(chartData);
                        }

                    } catch (JSONException e) {
                        e.printStackTrace();
                    }
                },
                error -> {
                    Toast.makeText(getApplicationContext(), "ERROR", Toast.LENGTH_LONG).show();
                });
        requestQueue.add(req);
        return chartDataList;
}

Answer 1

The Response function is a callback that will be executed after your request has processed/server has responded. I would recommend executing your logic that depends on the response data within your Response function callback. This is non-blocking but works with the asynchronous design of Volley:

 public List<ChartData> getVolleyResponse() {
    requestQueue = Volley.newRequestQueue(getApplicationContext());
    JsonObjectRequest req = new JsonObjectRequest(
            Request.Method.GET,
            urlCreator(getCoinName()),
            null,
            response -> {
                try {
                    JSONArray arr = response.getJSONArray("prices");
                    ChartData chartData = new ChartData();
                    for (int i = 0; i < arr.length(); i++) {
                        JSONArray jsonArray = arr.getJSONArray(i);
                        chartData.setTimeStamp(timeStampConverter(jsonArray.getString(0)));
                        chartData.setCost(jsonArray.getDouble(1));
                        chartDataList.add(chartData);
                    }
                    
                    // The request has processed/server has responded.
                    // Do something with your response here.
                    // ...

                } catch (JSONException e) {
                    e.printStackTrace();
                }
            },
            error -> {
                Toast.makeText(getApplicationContext(), "ERROR", Toast.LENGTH_LONG).show();
            });
    requestQueue.add(req);
    
    // We're handling the response asynchronously, so there shouldn't be anything to return here.
}