org.json.JSONException：值

Question

我正在尝试使用 c# 的 REST 服务在 android 应用程序中获取 json 数据。 它抛出一个错误：

org.json.JSONException: Value <?xml of type java.lang.String cannot be converted to JSONObject

我在上一个问题中搜索了 SO，但找不到任何有用的信息。

我尝试过的是：-

在 C# 中

 public DataTable TestCheckEgrasUserLogin()
    {
        DataTable dt = new DataTable();
        GenralFunction gf = new GenralFunction();
        SqlParameter[] PM = new SqlParameter[2];
        PM[0] = new SqlParameter("@UserName", SqlDbType.VarChar, 50) { Value = UserName };
        PM[1] = new SqlParameter("@Password", SqlDbType.VarChar, 50) { Value = Password };
        dt = gf.Filldatatablevalue(PM, "TestegAndroidUserLoginInfo", dt, null);
        return dt;
    }

我已经通过在 Visual Studio 中运行对其进行了测试，它运行良好并带来数据。

在安卓中：-

   public class MainActivity extends Activity {
   private final static String SERVICE_URI = "`serviceUrl`";

    @Override
   protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
        StrictMode.setThreadPolicy(policy);
        Button button = (Button) findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                try
                {

                    final EditText usernametxt = (EditText) findViewById(R.id.txtUser);
                    final EditText passwordtxt = (EditText) findViewById(R.id.txtPassword);

                    String username;
                    String Password;
                    username=usernametxt.getText().toString();
                    Password=passwordtxt.getText().toString();


                    if(username=="" || Password=="")
                    {
                        MessageBox("Please Enter UserName or Password");
                    }
                    else if (username.length()<1 || Password.length()<1)
                    {
                        MessageBox("Please Enter Credential Details");
                    }
                    StrictMode.setThreadPolicy(new StrictMode.ThreadPolicy.Builder().permitNetwork().build());
                    final    HttpGet request = new HttpGet(SERVICE_URI+username+"/Password/"+Password);
                    request.setHeader("Accept", "application/json");
                    request.setHeader("Content-type","application/json; charset=utf-8");

                    final    DefaultHttpClient httpClient = new DefaultHttpClient(new BasicHttpParams());

                     final   HttpResponse response = httpClient.execute(request);

                    final    HttpEntity responseEntity = response.getEntity();

                    // Read response data into buffer

                    char[] buffer = new char[(int)responseEntity.getContentLength()];
                    String tmpStr10 =  String.valueOf(buffer.length);

                    InputStream stream = responseEntity.getContent();

                    InputStreamReader reader = new InputStreamReader(stream);
                    int sizeOfJSONFile = stream.available();
                                            reader.read(buffer);
                    stream.close();

                    JSONObject vehicle = new JSONObject(new String(buffer));  ** /////Error Comes here**

                    JSONArray plates=new JSONArray(vehicle.getString("CheckEgrasLoginResult"));

                    Bundle B=new Bundle();

                    String UserName= null;
                    String UserId =null;

                    Intent i = new Intent(getApplicationContext(), com.example.nic.newdemosecond.detailsact.class);
                    for (int j = 0; j < plates.length(); ++j) {
                        JSONObject Veh = new JSONObject(plates.getString(j));
                        UserName =  Veh.getString("UserName");
                        UserId =  Veh.getString("UserId");
                    }

                    i.putExtra("UserName", UserName);
                    i.putExtra("UserId", UserId);

                    startActivity(i);
                }
                catch (Exception e)
                {
                    MessageBox("Invalid Login");

                }
            }
        }) ;
}

错误出现在我声明JsonObject 。 由于我是 android 新手，我无法捕捉到这个错误。

任何帮助，将不胜感激 ！

Answer 1

HttpClient、DefaultHttpClient 已弃用，它们会耗尽电池电量，并在 android 中增加带宽。 使用 HttpURLConnection 而不是按照本教程http://terrapinssky.blogspot.in/2015/10/android-get-and-parse-json-file-from.html

Answer 2

您必须使用JavaScriptSerializer返回 Json 而不是XML ，如下所示

System.Web.Script.Serialization.JavaScriptSerializer serializer = new System.Web.Script.Serialization.JavaScriptSerializer();
List<Dictionary<string, object>> rows = new List<Dictionary<string, object>>();
            Dictionary<string, object> row;
            foreach (DataRow dr in dt.Rows)
            {
                row = new Dictionary<string, object>();
                foreach (DataColumn col in dt.Columns)
                {
                    row.Add(col.ColumnName, dr[col]);
                }
                rows.Add(row);
            }

最后返回 Json 之类的，

return serializer.Serialize(rows);

注意：有关详细信息，请参阅此答案，并根据需要对其进行修改。