Android:如何使用Volley处理来自服务器的消息错误？

Question

我正在使用Volley为我的Android应用程序从我的服务器获取数据.除了从我的服务器处理错误之外,它运行良好.我的服务器在出错时发送此响应:

{
    "status": 400,
    "message": "Errors (2): A name is required- Julien is already used. Not creating."
}

我的目标是获取消息,然后将其显示在Toast.我按照一些示例来了解如何执行此操作,但它不起作用.

有我的错误监听器:

public void onErrorResponse(VolleyError error) {
            int  statusCode = error.networkResponse.statusCode;
            NetworkResponse response = error.networkResponse;

            Log.d("testerror",""+statusCode+" "+response.data);
            // Handle your error types accordingly.For Timeout & No connection error, you can show 'retry' button.
            // For AuthFailure, you can re login with user credentials.
            // For ClientError, 400 & 401, Errors happening on client side when sending api request.
            // In this case you can check how client is forming the api and debug accordingly.
            // For ServerError 5xx, you can do retry or handle accordingly.
            if( error instanceof NetworkError) {
            } else if( error instanceof ClientError) {
            } else if( error instanceof ServerError) {
            } else if( error instanceof AuthFailureError) {
            } else if( error instanceof ParseError) {
            } else if( error instanceof NoConnectionError) {
            } else if( error instanceof TimeoutError) {
            }
            showProgress(false);
            mPasswordView.setError(getString(R.string.error_incorrect_password));
            mPasswordView.requestFocus();

        }

还有调试器的结果: testerror:400 [B @ 430b8d60

编辑:此外我的error.getMessage()为null.

所以我不明白为什么我的变量response.data不是我服务器的响应.

如果有人知道如何从我的服务器获取消息,那将是很酷的.

谢谢,

Answer 1

我已经实现了类似的东西,而且相对简单.你的日志消息打印出看起来像乱码的东西,因为response.data它实际上是一个字节数组 - 而不是a String.另外,a VolleyError实际上只是一个扩展Exception,因此Exception .getMessage()可能不会返回您要查找的内容,除非您覆盖解析方法以解析VolleyError扩展Request类中的内容.处理这个问题的一个基本方法是执行以下操作:

//In your extended request class
@Override
protected VolleyError parseNetworkError(VolleyError volleyError){
        if(volleyError.networkResponse != null && volleyError.networkResponse.data != null){
                VolleyError error = new VolleyError(new String(volleyError.networkResponse.data));
                volleyError = error;
            }

        return volleyError;
    }
}

如果将其添加到扩展Request类中,则getMessage()至少应该不返回null.不过,我通常不会为此烦恼,因为从你的onErrorResponse(VolleyError e)方法中完成这一切很容易.

您应该使用JSON库来简化操作 - 例如我使用Gson,或者您可以使用JSONObject不需要额外外部库的Apache .第一步是从服务器发送响应JSON String(以与我刚才演示的方式类似的方式),然后您可以选择将其转换为JSONObject(使用apache的JSONObjects和JsonArrays,或者您选择的其他库)或者只是解析String自己.在那之后,你只需要显示Toast.

这里有一些示例代码可以帮助您入门:

public void onErrorResponse(VolleyError error) {
     String json = null;

     NetworkResponse response = error.networkResponse;
     if(response != null && response.data != null){
         switch(response.statusCode){
             case 400:
                  json = new String(response.data);
                  json = trimMessage(json, "message");
                  if(json != null) displayMessage(json);
                  break;
             }
            //Additional cases
     }
}

public String trimMessage(String json, String key){
    String trimmedString = null;

    try{
        JSONObject obj = new JSONObject(json);
        trimmedString = obj.getString(key);
    } catch(JSONException e){
        e.printStackTrace();
        return null;
    }

    return trimmedString;
}

//Somewhere that has access to a context
public void displayMessage(String toastString){
    Toast.makeText(context, toastString, Toast.LENGTH_LONG).show();
}

Answer 2

尝试这个类来处理所有错误

public class VolleyErrorHelper {
        /**
         * Returns appropriate message which is to be displayed to the user
         * against the specified error object.
         *
         * @param error
         * @param context
         * @return
         */

        public static String getMessage (Object error , Context context){
            if(error instanceof TimeoutError){
                return context.getResources().getString(R.string.timeout);
            }else if (isServerProblem(error)){
                return handleServerError(error ,context);

            }else if(isNetworkProblem(error)){
                return context.getResources().getString(R.string.nointernet);
            }
            return context.getResources().getString(R.string.generic_error);

        }

        private static String handleServerError(Object error, Context context) {

            VolleyError er = (VolleyError)error;
            NetworkResponse response = er.networkResponse;
            if(response != null){
                switch (response.statusCode){

                    case 404:
                    case 422:
                    case 401:
                        try {
                            // server might return error like this { "error": "Some error occured" }
                            // Use "Gson" to parse the result
                            HashMap<String, String> result = new Gson().fromJson(new String(response.data),
                                    new TypeToken<Map<String, String>>() {
                                    }.getType());

                            if (result != null && result.containsKey("error")) {
                                return result.get("error");
                            }

                        } catch (Exception e) {
                            e.printStackTrace();
                        }
                        // invalid request
                        return ((VolleyError) error).getMessage();

                    default:
                        return context.getResources().getString(R.string.timeout);
                }
            }

            return context.getResources().getString(R.string.generic_error);
        }

        private static boolean isServerProblem(Object error) {
            return (error instanceof ServerError || error instanceof AuthFailureError);
        }

        private static boolean isNetworkProblem (Object error){
            return (error instanceof NetworkError || error instanceof NoConnectionError);
        }