Android - How to Represent JSON Information from URL through GSON

Question

I have been attempting to retrieve information from an online JSON Source using a URL. I initially got the information parsed to a TextView in Android, however I got ALL Information from the JSON. Below is a screenshot of what I am referring to.

Text View Showing All Data In Json

Essentially, What I want is to just show the Location, so in the above example, Oslo, in Norway in one Textview, then in another show the Current Moon Phase for that location, so - using the above example again, Waxing Crescent.

This is the JSON I am using.

{
  "version": 2,
  "locations": [{
    "id": "187",
    "geo": {
      "name": "Oslo",
      "country": {
        "id": "no",
        "name": "Norway"
      },
      "latitude": 59.913,
      "longitude": 10.740
    },
    "astronomy": {
      "objects": [{
        "name": "moon",
        "days": [{
          "date": "2018-09-13",
          "events": [],
          "moonphase": "waxingcrescent"
        }]
      }]
    }
  }]
}

To parse the JSON to the Textview showing all the data I used the following.

JSONObject jo = new JSONObject(data);
            JSONArray locations = jo.getJSONArray("locations");

            for (int i = 0; i < locations.length(); ++i) {
                JSONObject loc = locations.getJSONObject(0);
                JSONObject geo = loc.getJSONObject("geo");

                JSONObject country = geo.getJSONObject("country");

                JSONObject astronomy = loc.getJSONObject("astronomy");
                JSONObject objects = astronomy.getJSONArray("objects").getJSONObject(0);
                JSONObject day = objects.getJSONArray("days").getJSONObject(0);

                StringBuilder result = new StringBuilder();
                String singleParsed = "Moon: "+ astronomy.getString("moonphase");


            }



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


        return null;
    }

    @RequiresApi(api = Build.VERSION_CODES.CUPCAKE)
    @Override
    protected void onPostExecute(Void aVoid) {
        super.onPostExecute(aVoid);

        MainActivity.fetcheddata.setText(this.data);


    }

NOTE: A String is created in the For Loop, Called "Single Parsed", This is what I want to put on the screen, however - once I call that variable, nothing shows on the screen. It only shows when using:

MainActivity.fetcheddata.setText(this.data);

But Not with the following, I do actually receive an error saying "Cannot Resolve Symbol, singleParsed as well.

MainActivity.fetcheddata.setText(this.singleParsed);

After some research and previous questions on Stack, I believe GSON is the way to go to do what I wish, however I have no idea where to start, or how to do the task using GSON.

All help is appreciated.

Answer 1

JSON Information from URL through GSON

Simple answer - Look at using Retrofit, and find a tutorial on it, as well as Gson

---

However

You don't need Gson to fix your problem, and I suggest fixing the problem at hand rather than going down an unnecessary path.

First, singleParsed is a local variable within a loop. Therefore, this.singleParsed doesn't exist. Or if it does, you never set it.

Secondly, let's assume you only have one location, so you don't need a loop. Similar to how you accessed the other JSON arrays, just get the first array item.

Finally, you'll need to understand how AsyncTask works, but my general recommended solution is at How to get the result of OnPostExecute() to main activity because AsyncTask is a separate class?

But, for this purpose, here is a simple example with AsyncTask<String, Void, String>

// protected String doInBackground(String... url) { // I assume you have this ??

    // String data = parseJsonFrom(url[0]);

    String singleParsed = "(none)";

    try {
        JSONObject jo = new JSONObject(data);
        JSONObject firstLocationAstronomy = jo
          .getJSONArray("locations").getJSONObject(0)
          .getJSONObject("astronomy");
        JSONObject firstDay = firstLocationAstronomy
          .getJSONArray("objects").getJSONObject(0)
          .getJSONArray("days").getJSONObject(0);
        singleParsed = firstDay.getString("moonphase");
    } catch (Exception e) { // TODO: catch a JSONParseException 
    }

    return singleParsed; // This is returned to onPostExecute, don't store a variable elsewhere

}

Then in the MainActivity, wherever you make this task, and set the text

new MoonPhaseTask() {
    @Override
    protected void onPostExecute(String moonPhase) {
        MainActivity.this.textView.setText("Phase: " + moonPhase);
    }
}.execute("some url");

What I want is to just show the Location, so in the above example, Oslo, in Norway in one Textview, then in another show the Current Moon Phase for that location

You can change the AsyncTask to return you the entire JSONObject to the onPostExecute, and parse the JSON there if you really wanted. Just the networking pieces need to be off the UI thread... parsing is not computationally expensive.