Question

我包含的代码是我的Asynctask，它从URL获取JSON并尝试解析它并将信息输出到屏幕上的TextViews。我假设问题在于onPostExecute块实际上将JSON信息传递给字符串并输出它但我无法弄清楚我做错了什么。昨晚我让它部分工作，但它只打印0和零。我已经做了一些改变，我在这里。

class GetStats extends AsyncTask<String, String, JSONObject> {

    private String api_key="d96236d2-6ee3-4cfd-afa7-f41bdbc11128";
    String region = MainActivity.region.toLowerCase();
    String name = MainActivity.name;
    String url = null;
    String encodedName = null;
    String encodedKey = null;
    String encodedRegion = null;

    // JSON Node Names
    String TAG_ID = "id";
    String TAG_NAME = "name";
    String TAG_PROFILEICONID = "profileIconId";
    String TAG_REVISIONDATE = "revisionDate";
    String TAG_SUMMONERLEVEL = "summonerLevel";

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        try {
            textId = (TextView) findViewById(R.id.id);
            textName = (TextView) findViewById(R.id.name);
            textProfileIconId = (TextView) findViewById(R.id.profileIconId);
            textRevisionDate = (TextView) findViewById(R.id.revisionDate);
            textSummonerLevel = (TextView) findViewById(R.id.summonerLevel);
            encodedName = URLEncoder.encode(name, "UTF-8");
            encodedKey = URLEncoder.encode(api_key, "UTF-8");
            encodedRegion = URLEncoder.encode(region, "UTF-8");
            url = "https://prod.api.pvp.net/api/lol/" + encodedRegion + "/v1.4/summoner/by-name/" + encodedName + "?api_key=" + encodedKey;

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

    }

    @Override
    protected JSONObject doInBackground(String... arg0) {
        JSONParser jParser = new JSONParser();

        // Get JSON from URL
        JSONObject json = jParser.getJSONFromUrl(url);
        JSONObject jb = null;

        try {
            jb = json.getJSONObject(encodedName);
        } catch (JSONException e) {
            e.printStackTrace();
        }
        return jb;
    }

    @Override
    protected void onPostExecute(JSONObject json) {
        try {
            // Storing JSON item to String
            String id = json.getString(TAG_ID);
            String name = json.getString(TAG_NAME);
            String icon = json.getString(TAG_PROFILEICONID);
            String revDate = json.getString(TAG_REVISIONDATE);
            String sumLevel = json.getString(TAG_SUMMONERLEVEL);

            // Putting JSON data in TextViews
            textId.setText(id);
            textName.setText(name);
            textProfileIconId.setText(icon);
            textRevisionDate.setText(revDate);
            textSummonerLevel.setText(sumLevel);

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

JSON预期结果示例：

 {"nv43":{"id":23591778,"name":"NV43","profileIconId":22,"summonerLevel":30,"revisionDate":1396737099000}}

错误：

04-07 13:32:18.359  22875-22875/? E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: edu.appdesign.leaguestats, PID: 22875
    java.lang.NullPointerException
            at edu.appdesign.leaguestats.StatsActivity$GetStats.onPostExecute(StatsActivity.java:110)
            at edu.appdesign.leaguestats.StatsActivity$GetStats.onPostExecute(StatsActivity.java:53)
            at android.os.AsyncTask.finish(AsyncTask.java)
            at android.os.AsyncTask.access$600(AsyncTask.java)
            at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java)
            at android.os.Handler.dispatchMessage(Handler.java)
            at android.os.Looper.loop(Looper.java)
            at android.app.ActivityThread.main(ActivityThread.java)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java)
            at dalvik.system.NativeStart.main(Native Method)

Answer 1

{ // json object node 
    "nv43": {  // jsonobject nv43
        "id": 23591778, 
        "name": "NV43",
        "profileIconId": 22,
        "summonerLevel": 30,
        "revisionDate": 1396737099000
    }
}

您错过了解析JSONObject nv43。

在doInBackground

JSONObject json = jParser.getJSONFromUrl(url);
JSONObject jb = json.getJSONObject("nv43"); 
return jb;

Answer 2

更改下面的onPostExecute（）方法

@Override
    protected void onPostExecute(JSONObject json) {
        try {
            JSONObject result = json.getJSONObject("nv43"); // First Create an Object of "nv43"
            // Storing JSON item to String
            String id = result.getString(TAG_ID);
            String name = result.getString(TAG_NAME);
            // Rest code

JSON对象无法打印到屏幕

2 个答案: