java - 使用Volley在Util类中调用Web服务后如何返回值？

Question

我想在从 Volley 中的 Web 服务获取响应并在 Activity 中调用值后返回字符串值。下面是我的代码；

Utils.java

    public static String getitemCountPrice(String cartId) {

    try {
        if (Utils.isNetworkAvailable(mContext)) {
            HashMap<String, String> params = new HashMap<>();
            params.put(CONSTANTS.API_param_cartid, cartId);
            params.put(CONSTANTS.API_param_token, Utils.getToken());
            JSONObject postdata = new JSONObject(params);

            try {
                YupITApplication.getJsonWithHTTPPostResponse(params, mContext, 1, (id, jsonResult) -> {
                    if (jsonResult.getString(mContext.getString(R.string.status)).equalsIgnoreCase(mContext.getString(R.string.success))) {
                        itemCountPrice = jsonResult.getJSONObject("Data").getString("Count") + ","
                                + jsonResult.getJSONObject("Data").getString("TotalPrice");
                        Log.e("itemCountPrice.............", "" + itemCountPrice);
                        // Here I get value
                    } else {
                        itemCountPrice = "0,0";
                    }
                }, Utils.cartitemcount, postdata);
            } catch (Exception e) {
                e.printStackTrace();
            }
        } else {
            Toast.makeText(mContext, mContext.getString(R.string.no_server_found), Toast.LENGTH_SHORT).show();
        }
    } catch (Exception e) {
        e.printStackTrace();
    }

    return itemCountPrice;
    // Here I get null and this is called before web service call
}

MainActivity.java

Utils.getitemCountPrice(cart_id));

每次我从上述方法中得到 null

Answer 1

您的 return 语句将在进行 API 调用后立即执行，并且不会等待响应，因为它是以同步方式编写的。您可以借助界面通知结果

interface APIListener{
  public void onResponse(String itemPrice);
}

你的方法看起来像这样

    public static void getitemCountPrice(String cartId, APIListener apiListener) {

        try {
            if (Utils.isNetworkAvailable(mContext)) {
                HashMap<String, String> params = new HashMap<>();
                params.put(CONSTANTS.API_param_cartid, cartId);
                params.put(CONSTANTS.API_param_token, Utils.getToken());
                JSONObject postdata = new JSONObject(params);

                try {
                    YupITApplication.getJsonWithHTTPPostResponse(params, mContext, 1, (id, jsonResult) -> {
                        if (jsonResult.getString(mContext.getString(R.string.status)).equalsIgnoreCase(mContext.getString(R.string.success))) {
                            itemCountPrice = jsonResult.getJSONObject("Data").getString("Count") + ","
                                    + jsonResult.getJSONObject("Data").getString("TotalPrice");
                            Log.e("itemCountPrice.............", "" + itemCountPrice);
    apiListener.onResponse(itemCountPrice);
                            // Here I get value
                        } else {
                            itemCountPrice = "0,0";
                            apiListener.onResponse(itemCountPrice);
                        }
                    }, Utils.cartitemcount, postdata);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            } else {
                Toast.makeText(mContext, mContext.getString(R.string.no_server_found), Toast.LENGTH_SHORT).show();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }