解析JSON以配置Android应用程序

Question

在我的Android应用程序中，我必须使用服务器上的JSON才能在应用程序中进行特定调整。我试图达到的目的是读取此json并将所有值存储到局部变量中以在应用程序内执行操作。

来自服务器的JSON：

[

    {
        "sett": " ",
        "glHdr": {
            "sm": [ ],
            "scleHPad": false,
            "st": "sbsm"
        },
        "colrBG": [
            23,
            105,
            184,
            100
        ],
        "colrTB": [
            0,
            0,
            0,
            0
        ],
        "colrTR": [
            255,
            255,
            255,
            100
        ],
        "glFtr": {
            "icoSz": "icoSzN",
            "sm": [ ],
            "scleHPad": false,
            "gvNR": 3,
            "gvHIT": false,
            "gvNC": 3,
            "st": "igsm"
        },
        "statBr": true
    },
    {
        "sm": [
            {
                "tbico": "b43-jeep.png",
                "t": "Welcome!",
                "w": "http://google.com/start",
                "st": "w",
                "wTBL": "wTBLN"
            },
            {
                "t": "Content screen title",
                "f": "Eltec%20Spec%20sheet%20Gim%20RD30W.pdf",
                "st": "f"
            },
            {
                "tbico": "109-chicken.png",
                "t": "Sub menu",
                "sm": [
                    {
                        "t": "Screen 1",
                        "st": "f"
                    },
                    {
                        "t": "Screen 2",
                        "w": "Http://google.com",
                        "st": "w",
                        "wTBL": "wTBLT"
                    }
                ],
                "st": "sm"
            },
            {
                "st": "f"
            }
        ],
        "st": "tbm"
    }

]

为了进行解析，我创建了Parse JSON类，并尝试提出在我的应用中读取和存储此JSON值的方法。

执行此操作的功能：

public void doScanAppConfigJson(){

private static final String = TAG_TITLE;
private static final String = TAG_WEB_ADDRESS;
private static final String = TAG_SCREEN_TYPE;
private static final String = TAG_FILENAME;


        JSONArray appConfig = null;

        // Function for looping json object via ParseJson class.
        //Creating JSON Parser instance
        JSONParser jParser = new JSONParser();

        //Getting json strings from url
        JSONObject jsonObject = jParser.getJSONFromUrl(url);

    try{
        //Getting array of settings
        appConfig = jsonObject.getJSONArray(ConfigConstants.TABLE_VIEW_SUB_MENU_CONFIG);
        //loop throw all the objects under -sm[]
        for (int i = 0; i < appConfig.length(); i++){

            JSONObject sm = appConfig.getJSONObject(i);

            //Now store each of this json in local constant var.

            String tabTitle = sm.getString(TAG_TITLE);

            String webAddress = sm.getString(TAG_WEB_ADDRESS);

            String screenType = sm.getString(TAG_SCREEN_TYPE);

            String fileName = sm.getString(TAG_FILENAME);

        }

    }catch (JSONException e){
        e.printStackTrace();

    }

    }

getJSONFromUrl方法：

public JSONObject getJSONFromUrl(String url) {

        //Global authentication for link username and password.
        Authenticator.setDefault(new Authenticator() {
            protected PasswordAuthentication getPasswordAuthentication(){

            return new PasswordAuthentication("username", "password".toCharArray());   
            }

        });

        // Making HTTP request
        try {
            // defaultHttpClient
            DefaultHttpClient httpClient = new DefaultHttpClient();
            HttpPost httpPost = new HttpPost(url);

            HttpResponse httpResponse = httpClient.execute(httpPost);
            HttpEntity httpEntity = httpResponse.getEntity();
            is = httpEntity.getContent();

        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        try {
            BufferedReader reader = new BufferedReader(new InputStreamReader(
                    is, "iso-8859-1"), 8);
            StringBuilder sb = new StringBuilder();
            String line = null;
            while ((line = reader.readLine()) != null) {
                sb.append(line + "\n");
            }
            is.close();
            json = sb.toString();
        } catch (Exception e) {
            Log.e("Buffer Error", "Error converting result " + e.toString());
        }

        // try parse the string to a JSON object
        try {
            jObj = new JSONObject(json);
        } catch (JSONException e) {
            Log.e("JSON Parser", "Error parsing data " + e.toString());
        }

        // return JSON String
        return jObj;

    }

我正在收到错误：settingsjava.lang.NullPointException在此但我已经定义了vars，请有人告诉我我如何解析JSON。我在正确的道路上实现答案吗？我的问题？

Answer 1

当前的json字符串格式为：

[  //<<<< JSONArray

    {   //<<<< JSONObject
       // other items here...
    }

]

此Json字符串内容JSONArray作为root元素而不是JSONObject。您将需要先将其转换为JSONArray，然后从中提取JSONObject：

JSONArray jsonObject = jParser.getJSONFromUrl(url);

也将getJSONFromUrl方法返回类型更改为JSONArray