java - 通过JSON解析显示错误信息

Question

当我的 WEBSERVICE 没有返回任何数据时，我想添加一条 toast 消息并使用户返回到主要 Activity ，并允许我进行更多解释。当用户搜索查询时，网络服务将数据返回到我的 JSON 字符串，如下所示。

08-30 00:36:07.917: D/JSON String(1891): {
08-30 00:36:07.917: D/JSON String(1891): "all" :    {
08-30 00:36:07.917: D/JSON String(1891):    "count" : 25,
08-30 00:36:07.917: D/JSON String(1891):    "questions" : [     {   
08-30 00:36:07.917: D/JSON String(1891):            "Id" : "20100728112033AAb4hTA",
08-30 00:36:07.917: D/JSON String(1891):            "Subject" : "What is the oldest a bitch can more or less safely breed?",
08-30 00:36:07.917: D/JSON String(1891):            "Content" : "Don't worry I'm not going to breed - both my bitches are getting neutered in the next year, as is my dog! Just that me and a friend were talking about it after talking to the man who gave me Misty (my border collie) who said she could still breed at 7 - I thought the oldest was 5?\n",
08-30 00:36:07.917: D/JSON String(1891):            "Date" : "2010-07-28 18:20:33",
08-30 00:36:07.917: D/JSON String(1891):            "Timestamp" : "1280341233",
08-30 00:36:07.917: D/JSON String(1891):            "Link" : "http://answers.yahoo.com/question/?qid=20100728112033AAb4hTA",
08-30 00:36:07.917: D/JSON String(1891):            "Type" : "Answered",
08-30 00:36:07.917: D/JSON String(1891):            "CategoryId" : 396546021,
08-30 00:36:07.917: D/JSON String(1891):            "CategoryName" : "Dogs",
08-30 00:36:07.917: D/JSON String(1891):            "UserId" : "cP16Ctgxaa",
08-30 00:36:07.917: D/JSON String(1891):            "UserNick" : "Kiko",
08-30 00:36:07.917: D/JSON String(1891):            "UserPhotoURL" : "http://l.yimg.com/dg/users/1t1USxJpxAAEBQOGZjBMW0-5Wp_EG.medium.jpg",
08-30 00:36:07.917: D/JSON String(1891):            "NumAnswers" : 8,
08-30 00:36:07.917: D/JSON String(1891):            "NumComments" : 0,
08-30 00:36:07.917: D/JSON String(1891):            "ChosenAnswer" : "You just \"imagined\" that ,dear...not \"thought\". & your imagination is WRONG.\r\n\r\n9 or even 10,for a healthy TOP-PRODUCING bitc-h.\r\n\r\n\r\n\r\n*&* bitches are SPAYED & dogs are CASTRATED......big scary correct ADULT words.",
08-30 00:36:07.917: D/JSON String(1891):            "ChosenAnswererId" : "clN6YITvaa",
08-30 00:36:07.917: D/JSON String(1891):            "ChosenAnswererNick" : "Debunker",
08-30 00:36:07.917: D/JSON String(1891):            "ChosenAnswerTimestamp" : "1280317077",
08-30 00:36:07.917: D/JSON String(1891):            "ChosenAnswerAwardTimestamp" : "1280835336"
08-30 00:36:07.917: D/JSON String(1891):        },      {

这是我如何解析这些数据以获取我想要的特定数据的代码

protected String doInBackground(String... args) {

    try {
        Intent in = getIntent();
        String searchTerm = in.getStringExtra("TAG_SEARCH");
        String query = URLEncoder.encode(searchTerm, "utf-8");
        String URL = "http://example.com";
        JSONParsser jParser = new JSONParsser();
        JSONObject json = jParser.readJSONFeed(URL);
        try {

            JSONArray questions = json.getJSONObject("all").getJSONArray("questions");

            for(int i = 0; i < questions.length(); i++) {
                JSONObject question = questions.getJSONObject(i);


            String Subject = question.getString(TAG_QUESTION_SUBJECT);
            String ChosenAnswer = question.getString(TAG_QUESTION_CHOSENANSWER);
            String Content = question.getString(TAG_QUESTION_CONTENT);


            }


        } catch (JSONException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    } catch (UnsupportedEncodingException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

        return TAG_QUESTION ;           

}

但是当用户搜索查询并且网络服务没有返回任何结果时，我的意思是网络服务数据有 "count": 0, 并且它在我的 JSON 字符串中看起来像这样看起来像这样。

09-02 00:25:55.466: D/JSON String(882): {
09-02 00:25:55.466: D/JSON String(882): "all" : {
09-02 00:25:55.466: D/JSON String(882):     "count" : 0,
09-02 00:25:55.466: D/JSON String(882):     "questions" : [     ]
09-02 00:25:55.466: D/JSON String(882):     }
09-02 00:25:55.466: D/JSON String(882): }

当发生这种情况时，我希望弹出一条 toast 消息并将用户返回到主要 Activity ，但我只是不知道如何在返回计数 0 时解析该数据。我已经知道我需要添加一个 if 语句在此位置

        try {
            // if statement here
            JSONArray questions = json.getJSONObject("all").getJSONArray("questions");

            for(int i = 0; i < questions.length(); i++) {
                JSONObject question = questions.getJSONObject(i);


            String Subject = question.getString(TAG_QUESTION_SUBJECT);
            String ChosenAnswer = question.getString(TAG_QUESTION_CHOSENANSWER);
            String Content = question.getString(TAG_QUESTION_CONTENT);

我需要知道如何解析 "count": 0, 以便我可以显示 toast 消息，然后将用户返回到主 Activity 。希望您能在这里看到我的想法，如果您在尝试理解我的意思时遇到任何问题，请告诉我。附言如果您想知道 JSONParsser 是什么，它就是我用来连接到网络服务的类，searchTerm 就是我传递 editText 并对其进行编码.

@Override
protected void onPostExecute(String file_URL) { 

    if(file_URL.equals("0")) { 
        pDialog.dismiss();
        Toast.makeText(ListView.this, "No data found", Toast.LENGTH_SHORT).show();
        finish();    

}else{

        if (pDialog.isShowing()) pDialog.dismiss();
        ListAdapter adapter = new SimpleAdapter(getBaseContext(), questionList,
                R.layout.listelements,
                new String[] { TAG_QUESTION_SUBJECT }, new int[] {
                R.id.Subject,});

        setListAdapter(adapter);
}

更新

        protected JSONObject doInBackground(String... args) {  

            JSONObject json = new JSONObject();
            try {
                Intent in = getIntent();
                String searchTerm = in.getStringExtra("TAG_SEARCH");
                String query = URLEncoder.encode(searchTerm, "utf-8");
                String URL = "http://example.com";
                JSONParsser jParser = new JSONParsser();

                    json = jParser.readJSONFeed(URL);
                } catch (UnsupportedEncodingException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }

                return json;           

            }

        @Override
        protected void onPostExecute(JSONObject json) { 

            int count = 0;
            try {
                count = json.getJSONObject("all").getInt("count");
            } catch (JSONException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            if(count>0) { 
                pDialog.dismiss();
                Toast.makeText(ListView.this, "No data found", Toast.LENGTH_SHORT).show();
                finish();    

        }else{

                try {

                    JSONArray questions = json.getJSONObject("all").getJSONArray("questions");

                    for(int i = 0; i < questions.length(); i++) {
                        JSONObject question = questions.getJSONObject(i);


                    String Subject = question.getString(TAG_QUESTION_SUBJECT);
                    String ChosenAnswer = question.getString(TAG_QUESTION_CHOSENANSWER);
                    String Content = question.getString(TAG_QUESTION_CONTENT);

                    HashMap<String, String> map = new HashMap<String, String>();

                    map.put(TAG_QUESTION_SUBJECT, Subject);
                    map.put(TAG_QUESTION_CONTENT, Content);
                    map.put(TAG_QUESTION_CHOSENANSWER, ChosenAnswer);

                    questionList.add(map);

                    pDialog.dismiss();
                    ListAdapter adapter = new SimpleAdapter(getBaseContext(), questionList,
                                R.layout.listelements,
                                new String[] { TAG_QUESTION_SUBJECT }, new int[] {
                                R.id.Subject,});

                        setListAdapter(adapter);
                    }

                } catch (JSONException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }

        }


    }

}

Answer 1

要获取count值，只需执行

int count = json.getJSONObject("all").getInt("count");

(您应该将 "count" 替换为最终变量，就像您对代码中的其他 JSONObject 所做的那样)

然后在你做之前添加一个if

JSONArray questions = json.getJSONObject("all").getJSONArray("questions");

但是您将无法在 doInBackground 方法中显示您的 toast，您必须返回结果(一个字符串)并将其显示在 onPostExecute() 。到目前为止，您没有返回正确的值，您返回的是 TAG_QUESTION，它必须是最终字符串，这意味着您的处理结果永远不会在方法之外使用。

更新

我认为你应该这样做:

首先，您不应该在 doInBackground() 中完成所有处理。在这个方法中，你应该只检索你的 json，返回它并在 onPostExecute() 中处理它。为此，您需要更改 AsyncTask，使其看起来像这样(注意最后一个参数的变化，从 String 到 JSONObject) :

private class yourAsyncTask extends AsyncTask<String, Void, JSONObject> {

这将告诉您的程序doInBackground() 的返回值将是JSONObject 类型。所以你接下来要做的是改变你的 doInBackground() 让它看起来像那样(再次注意返回值的变化，从 String 到 JSONObject :

protected JSONObject doInBackground(String... args) {
    JSONObject json = new JSONObject();
    try {
        Intent in = getIntent();
        String searchTerm = in.getStringExtra("TAG_SEARCH");
        String query = URLEncoder.encode(searchTerm, "utf-8");
        String URL = "http://example.com";
        JSONParsser jParser = new JSONParsser();

        try {
            json = jParser.readJSONFeed(URL);
        } catch (JSONException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    } catch (UnsupportedEncodingException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

    return json;           

}

然后将onPostExecute()中的参数类型改为JSONObject，检查count值后做你的处理:

@Override
protected void onPostExecute(JSONObject json) { 

    int count = json.getJSONObject("all").getInt("count");
    if(count>0) {   // There are some questions to retrieve

        /*  In this part I just copied what you put in your question, 
            I don't know what your goal is so I can't help much, 
            but you have the logic to do so */

        JSONArray questions = json.getJSONObject("all").getJSONArray("questions");

        for(int i = 0; i < questions.length(); i++) {
            JSONObject question = questions.getJSONObject(i);


        String Subject = question.getString(TAG_QUESTION_SUBJECT);
        String ChosenAnswer = question.getString(TAG_QUESTION_CHOSENANSWER);
        String Content = question.getString(TAG_QUESTION_CONTENT);

        if (pDialog.isShowing()) pDialog.dismiss();
        ListAdapter adapter = new SimpleAdapter(getBaseContext(), questionList,
            R.layout.listelements,
            new String[] { TAG_QUESTION_SUBJECT }, new int[] {
            R.id.Subject,});

        setListAdapter(adapter);

    } else {

        Toast.makeText(ListView.this, "No data found", Toast.LENGTH_SHORT).show();
        finish();    

    }

}