Java get JSON in Android TextView from URL

Question

I want to get a JSON response from a php displayed in a TextView in Android Studio. I now have this code to do that, but it doesn't work. As far as I can see it doesn't even run when the app is opened.

public class MainActivity extends Activity {

private SQLiteHandler db;
private SessionManager session;

private String readAll(Reader rd) throws IOException {
    StringBuilder sb = new StringBuilder();
    int cp;
    while ((cp = rd.read()) != -1) {
        sb.append((char) cp);
    }
    return sb.toString();
}

public JSONObject readJsonFromUrl(String url) throws IOException, JSONException {
    InputStream is = new URL(url).openStream();
    try {
        BufferedReader rd = new BufferedReader(new InputStreamReader(is, Charset.forName("UTF-8")));
        String jsonText = readAll(rd);
        JSONObject json = new JSONObject(jsonText);
        return json;
    } finally {
        is.close();
    }
}

public void main(String[] args) throws IOException, JSONException {
    TextView txtUser = (TextView) findViewById(R.id.user);
    JSONObject json = readJsonFromUrl("http://piggybank.wordmediavormgever.nl/getSaldo.php");
    System.out.println(json.toString());
    System.out.println(json.getString("saldo"));
    try {
        JSONObject jsonObject = new JSONObject();
        String response = jsonObject.getString("saldo");
        txtUser.setText(response);

    } catch (JSONException e) {

        e.printStackTrace();
    }
}

Can anyone see what I'm doing wrong? The response from the url is {"saldo":783}.

you are trying to start an android activity with a `main` method? — Suraj Rao, Sep 06 '17 at 06:29
I just got this piece of code from this site, I'm not very experienced with coding myself (yet) — Roan, Sep 06 '17 at 06:31
Java or Android ? for Android see those: https://stackoverflow.com/questions/33229869/get-json-data-from-url-using-android *and* https://stackoverflow.com/questions/13196234/simple-parse-json-from-url-on-android-and-display-in-listview — AsfK, Sep 06 '17 at 06:31

Navin Gupta · Answer 1 · 2017-09-06T07:03:00.287

I think the problem is here in main function in try block

JSONObject jsonObject = new JSONObject();
String response = jsonObject.getString("saldo");
txtUser.setText(response);

your jsonObject is empty You should call

String response = json.getString("saldo");
txtUser.setText(response);

One more thing when you are making some network call you should do it in background thread , not on UI thread.(readJsonFromUrl method should be called in background thread)

as Nguyễn Trung Hiếu's answer suggested

Nguyễn Trung Hiếu · Accepted Answer · 2017-09-06T07:13:02.227

Try it!

remove

   JSONObject jsonObject = new JSONObject();

And use

   JSONObject json = readJsonFromUrl("http://piggybank.wordmediavormgever.nl/getSaldo.php");
  try {
    String response = json.getString("saldo");
    Log.e("AAAAAAAAA %s", response);

}

You must call it in AsyncTask. Completed code!!!

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_test2);
    new GetDataSync().execute();
}

String saldo = "";

public class GetDataSync extends AsyncTask<Void, Void, Void> {


    @Override
    protected Void doInBackground(Void... params) {
        try {
            getData();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (JSONException e) {
            e.printStackTrace();
        }
        return null;
    }

    @Override
    protected void onPostExecute(Void aVoid) {
        super.onPostExecute(aVoid);
        txtUser.setText(saldo);
    }
}

private void getData() throws IOException, JSONException {
    JSONObject json = readJsonFromUrl("http://piggybank.wordmediavormgever.nl/getSaldo.php");
    try {
        String response = json.getString("saldo");
        Log.e("AAAAAAAAA %s", response);
        saldo = response;

    } catch (JSONException e) {

        e.printStackTrace();
    }
}

private String readAll(Reader rd) throws IOException {
    StringBuilder sb = new StringBuilder();
    int cp;
    while ((cp = rd.read()) != -1) {
        sb.append((char) cp);
    }
    return sb.toString();
}

public JSONObject readJsonFromUrl(String url) throws IOException, JSONException {
    InputStream is = new URL(url).openStream();
    try {
        BufferedReader rd = new BufferedReader(new InputStreamReader(is, Charset.forName("UTF-8")));
        String jsonText = readAll(rd);
        JSONObject json = new JSONObject(jsonText);
        return json;
    } finally {
        is.close();
    }
}

The `ButterKnife.bind` thing, what is that for? `Cannot resolve symbol 'ButterKnife'` — Roan, Sep 06 '17 at 07:04
Okay, if I run this code I get this response in the Android Monitor: `E/AAAAAAAAA %s: 0`. Nothing else happens, And it isn't setting the text in the TextView. — Roan, Sep 06 '17 at 07:09
Yes, the code works now, thanks! But now I have a new problem. When I login with my app it doens't remember I'm logged in. So the server gives as response `0`. Is there an easy way to solve this? — Roan, Sep 06 '17 at 07:17
This can not be resolved with all the information above. You need to add the source code — Nguyễn Trung Hiếu, Sep 06 '17 at 07:19

Java get JSON in Android TextView from URL

2 Answers2