Calling methods after new Class.execute() crash, android studio

Question

Basically, i have an app that uses JSON. I get the JSON in new HentData.execute(); and pass it to a string variable. But when I try to acutally do something with it my program crashes.

HentData extends AsyncTask, I know it gives me a JSON string that works

INSIDE oncreate()

new HentData().execute(); 
jsonToArray();
arrayToText();

This crashes

But when I run them like this it works, do I have to close the HentData class somehow?

protected void onPostExecute(String resultat){
    json_string = resultat;
    jsonToArray();
    arrayToText(); 
}

This is my doInBackground()

protected String doInBackground(Void... voids){
        try {
            URL url = new URL(json_url);
            HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
            InputStream IS = httpURLConnection.getInputStream();
            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(IS));
            StringBuilder sb = new StringBuilder();
            while((json_string = bufferedReader.readLine())!=null){
                sb.append(json_string+"\n");
            }

            bufferedReader.close();
            IS.close();
            httpURLConnection.disconnect();
            return sb.toString().trim();
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        return null;
    }

score 0 · Accepted Answer · edited May 23 '17 at 10:30

0

But when I run them like this it works, do I have to close the HentData class somehow?
protected void onPostExecute(String resultat){
    json_string = resultat;
    jsonToArray();
    arrayToText(); 
}

You don't have to close anything. This works because "async" in AsyncTask makes the code run in the background.

In other words,

new HentData().execute();  // Not waiting for result
jsonToArray(); // Continue on, even though there is no result yet --> error
arrayToText();

If you want a more flexible way to get results, see How to get the result of OnPostExecute() to main activity because AsyncTask is a separate class?

If you hate writing AsyncTasks (for HTTP methods), see Comparison of Android networking libraries: OkHTTP, Retrofit, and Volley

edited May 23 '17 at 10:30

Community

1
1

answered Nov 20 '16 at 01:19

OneCricketeer

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Would a while(json_string==""){ } work after HentData? – Litenhundvilikkeinn Nov 20 '16 at 01:21
**No** 1) That is not how you compare strings 2) That will freeze the UI, and make the app crash even worse – OneCricketeer Nov 20 '16 at 01:25
Thanks for the help, I think I understand now. I just put a a method in onPostExecute that is a "continuation" of onCreate, is that a ok way to do it? – Litenhundvilikkeinn Nov 20 '16 at 01:35
`onPostExecute` is a continuation of `doInBackground`, which is a continuation of `execute`, yes. Only put things that need the result of the asynctask within or after `onPostExecute` – OneCricketeer Nov 20 '16 at 01:37

Calling methods after new Class.execute() crash, android studio

1 Answers1