android - got stuck when a asynctask in another asynctask(OK, getting result from asynctask is provided)

Question

I've tried to implement a asynctask in another asynctask, but it got stuck. When I clicked the buttun to trigger the first asynctask, the second asynctask in the first one does not execute when the first is completed and when I tried to click the button again, the button gave no response.

java:

public class BackgroundTask extends AsyncTask<String, Void, String>{

String task = "";
Context context;
String user_name = "";
String user_ac = "";
String user_pw = "";

BackgroundTask (Context ctx){
    context = ctx;
}

@Override
protected String doInBackground(String... params) {
    String register_url = "http://www.minigameserver.square7.ch/register.php";
    String login_url = "http://www.minigameserver.square7.ch/login.php";
    String get_userID_url = "http://www.minigameserver.square7.ch/get_userID.php";
    String task_url = "";
    task = params[0];

    if(task.equals("register")){
        task_url = register_url;
        user_name = params[1];
        user_ac = params[2];
        user_pw = params[3];
    }
    if(task.equals("login")){
        task_url = login_url;
        user_ac = params[1];
        user_pw = params[2];
    }
    if(task.equals("get_userID")){
        task_url = get_userID_url;
        user_ac = params[1];
    }
        try {
            URL url = new URL(task_url);
            HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
            httpURLConnection.setRequestMethod("POST");
            httpURLConnection.setDoOutput(true);
            httpURLConnection.setDoInput(true);
            httpURLConnection.connect();
            OutputStream OS = httpURLConnection.getOutputStream();
            BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(OS, "UTF-8"));
            String data = "";
            if(task.equals("register")){
                data = URLEncoder.encode("user_name", "UTF-8") + "=" + URLEncoder.encode(user_name, "UTF-8") + "&" +
                        URLEncoder.encode("user_ac", "UTF-8") + "=" + URLEncoder.encode(user_ac, "UTF-8") + "&" +
                        URLEncoder.encode("user_pw", "UTF-8") + "=" + URLEncoder.encode(user_pw, "UTF-8");
            }
            if(task.equals("login")){
                data = URLEncoder.encode("user_ac", "UTF-8") + "=" + URLEncoder.encode(user_ac, "UTF-8") + "&" +
                        URLEncoder.encode("user_pw", "UTF-8") + "=" + URLEncoder.encode(user_pw, "UTF-8");
            }
            if(task.equals("get_userID")){
                data = URLEncoder.encode("user_ac", "UTF-8") + "=" + URLEncoder.encode(user_ac, "UTF-8");
            }
            bufferedWriter.write(data);
            bufferedWriter.flush();
            bufferedWriter.close();
            OS.close();

            int responseCode = httpURLConnection.getResponseCode();
            if (responseCode == 200) {
                InputStream IS = httpURLConnection.getInputStream();
                BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(IS));
                StringBuilder result = new StringBuilder();
                String getresult = "";
                while ((getresult = bufferedReader.readLine()) != null) {
                    result.append(getresult);
                }
                bufferedReader.close();
                IS.close();
                String result_newline = result.toString();
                result_newline = result_newline.replace("\\n", System.getProperty("line.separator"));
                return result_newline;
            }

            httpURLConnection.disconnect();
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return "fail!";

}

@Override
protected void onPostExecute(String result) {
    super.onPreExecute();
    if(task.equals("get_userID")){
        MainActivity.user_ID = result;
        Toast.makeText(context,"GET",Toast.LENGTH_LONG);
    }
    if(task.equals("register") || task.equals("login")){
        //Toast.makeText(context,result,Toast.LENGTH_LONG).show();
        BackgroundTask get_userID_task = new BackgroundTask(context);
        get_userID_task.execute("get_userID",user_ac);
    }

}
}

I implemented the second asynctask in the onPostExecute of the first one. Can anyone point out where I got wrong?

---

Update:

    if(task.equals("register") || task.equals("login")){
        MainActivity.user_ID = result;
        Toast.makeText(context,MainActivity.user_ID,Toast.LENGTH_LONG).show();
        //BackgroundTask get_userID_task = new BackgroundTask(context);
        //get_userID_task.execute("get_userID",user_ac);
    }

The message showed what I expected. When I commented out the second asynctask, the button still could not trigger again. When I ommented out MainActivity.user_ID = result; and related stuff, the button could trigger again.

---

Update2:

java:

public interface AsyncResponse {
    void processFinish();
}

public class BackgroundTask extends AsyncTask<String, Void, String>{
    AsyncResponse delegate = null;
    ...
        protected void onPostExecute(String result) {
            ...
            delegate.processFinish();
        }
}

// MainActivity has a button to go to login 
public class login extends AppCompatActivity implements AsyncResponse{
    ...
    BackgroundTask backgroundTask = new BackgroundTask(this);
    backgroundTask.delegate = this;
    backgroundTask.execute("login",user_ac_s,user_pw_s);

    public void processFinish(){
    if(!MainActivity.user_ID.equals("0"))
        finish();
    }
}

Actually, I want to finish the login page and go back to MainActivity after getting the user ID from Asynctask. But, it stopped unfortunately when the user login successfully.

New post: android - finish the current activity only after the asynctask finishes