Logcat Fehler android Studio Programmierung Fragmente

Question

Meine Fragmentklasse analysiert Informationen aus einer JSON-Datei. Aber das war zuerst eine Aktivität und das ist mein erster Versuch, dies zu einem Fragment zu machen.

mein Fragment Klasse:

public class salahtimesparser extends Fragment { 
    View rootView; 
    TextView fajrTV; 
    TextView zuhrTV; 
    TextView asrTV; 
    TextView maghribTV; 
    TextView ishaTV; 

    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 
     View rootView = inflater.inflate(R.layout.fragment_salahtimesparser, container, false); 
     new GetMethodEx().execute("http://muslimsalat.com/11717/daily/4.json?key=ea4417ebf152c478082e1ff6a1a759d9"); 
     return rootView;} 

    public class GetMethodEx extends AsyncTask<String, Void, InputStream> { 

     @Override 
     protected void onPreExecute() { 
      super.onPreExecute(); 
      fajrTV = (TextView) rootView.findViewById(R.id.fajr); 
      zuhrTV = (TextView) rootView.findViewById(R.id.zuhr); 
      asrTV = (TextView) rootView.findViewById(R.id.asr); 
      maghribTV = (TextView) rootView.findViewById(R.id.maghrib); 
      ishaTV = (TextView) rootView.findViewById(R.id.isha); 
     } 

     @Override 
     protected InputStream doInBackground(String... params) { 
      try { 
       HttpClient client = new DefaultHttpClient(); 
       HttpPost post = new HttpPost(params[0]); 
       HttpResponse response = client.execute(post); 
       int status = response.getStatusLine().getStatusCode(); 
       if (status == 200) { 
        HttpEntity entity = response.getEntity(); 
        InputStream in = entity.getContent(); 
        return in; 
       } 
      } catch (IOException e) { 
       e.printStackTrace(); 
      } 
      return null; 
     } 

     @Override 
     protected void onPostExecute(InputStream in) { 
      super.onPostExecute(in); 
      try { 
       JsonReader reader = new JsonReader(new InputStreamReader(in, "UTF-8")); 

       String fajr = null; 
       String zuhr = null; 
       String asr = null; 
       String maghrib = null; 
       String isha = null; 

       reader.beginObject(); 
       while (reader.hasNext()) { 
        String name = reader.nextName(); 
        if (name.equals("items")) { 
         reader.beginArray(); 
         while (reader.hasNext()) { 
          reader.beginObject(); 
          while (reader.hasNext()) { 
           String innerName = reader.nextName(); 
           final boolean isInnerNull = reader.peek() == JsonToken.NULL; 
           if (innerName.equals("fajr") && !isInnerNull) { 
            fajr = reader.nextString(); 
           } else if (innerName.equals("dhuhr") && !isInnerNull) { 
            zuhr = reader.nextString(); 
           } else if (innerName.equals("asr") && !isInnerNull) { 
            asr = reader.nextString(); 
           } else if (innerName.equals("maghrib") && !isInnerNull) { 
            maghrib = reader.nextString(); 
           } else if (innerName.equals("isha") && !isInnerNull) { 
            isha = reader.nextString(); 
           } else { 
            reader.skipValue(); 
           } 
          } 
          reader.endObject(); 
         } 
         reader.endArray(); 
        } else { 
         reader.skipValue(); 
        } 
       } 
       reader.endObject(); 
       reader.close(); 

       fajrTV.setText(fajr); 
       zuhrTV.setText(zuhr); 
       asrTV.setText(asr); 
       maghribTV.setText(maghrib); 
       ishaTV.setText(isha); 

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


    public boolean onCreateOptionsMenu(Menu menu) { 
     // Inflate the menu; this adds items to the action bar if it is present. 
     getActivity().getMenuInflater().inflate(R.menu.main2, menu); 
     return true; 
    } 

    @Override 
    public boolean onOptionsItemSelected(MenuItem item) { 
     // Handle action bar item clicks here. The action bar will 
     // automatically handle clicks on the Home/Up button, so long 
     // as you specify a parent activity in AndroidManifest.xml. 
     int id = item.getItemId(); 

     //noinspection SimplifiableIfStatement 
     if (id == R.id.action_settings) { 
      return true; 
     } 

     return super.onOptionsItemSelected(item); 
    } 

}

Dies geschieht, wenn die App stürzt ab, wenn ich auf der Anwendung die Option klicken. irgendwelche Vorschläge, wie das zu beheben?

Logcat:

java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View 
android.view.View.findViewById(int)' on a null object reference 

    at com.kazam.salahtimes.salahtimesparser$GetMethodEx.onPreExecute(salahtimesparser.java:45) 
    at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:587) 
    at android.os.AsyncTask.execute(AsyncTask.java:535) 
    at com.kazam.salahtimes.salahtimesparser.onCreateView(salahtimesparser.java:37) 
    at android.support.v4.app.Fragment.performCreateView(Fragment.java:1974) 
    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1067) 
    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1252) 
    at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:738) 
    at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1617) 
    at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:517) 
    at android.os.Handler.handleCallback(Handler.java:739) 
    at android.os.Handler.dispatchMessage(Handler.java:95) 
    at android.os.Looper.loop(Looper.java:145) 
    at android.app.ActivityThread.main(ActivityThread.java:5832) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at java.lang.reflect.Method.invoke(Method.java:372) 
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1399) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194) 

Answer 1

findViewById nicht mit Fragmenten arbeiten. Sie müssen so etwas wie unten

ImageView imageView = (ImageView) getView().findViewById(R.id.foo); 

Answer 2

NPE, weil Ihr RootView in onCreateView() lokales Objekt ist

@Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 
     //don't declare again use the global object rootView 
     rootView = inflater.inflate(R.layout.fragment_salahtimesparser, container, false); 
     new GetMethodEx().execute("http://muslimsalat.com/11717/daily/4.json?key=ea4417ebf152c478082e1ff6a1a759d9"); 
     return rootView; 
} 

Happy_Coding tun;

Answer 3

Sie können viewById in onCreateView stattdessen mithilfe von onPreExecute anzeigen, da Ihr View-Objekt nicht global deklariert ist.

Versuchen Sie dieses Stück Code:

@Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { View rootView = inflater.inflate(R.layout.fragment_salahtimesparser, container, false); fajrTV = (TextView) rootView.findViewById(R.id.fajr); zuhrTV = (TextView) rootView.findViewById(R.id.zuhr); asrTV = (TextView) rootView.findViewById(R.id.asr); maghribTV = (TextView) rootView.findViewById(R.id.maghrib); ishaTV = (TextView) rootView.findViewById(R.id.isha); new GetMethodEx().execute("http://muslimsalat.com/11717/daily/4.json?key=ea4417ebf152c478082e1ff6a1a759d9"); return rootView;} 

Answer 4

Verwenden

if(getView()!=null){ 
fajrTV.setText(fajr); 
zuhrTV.setText(zuhr); 
asrTV.setText(asr); 
maghribTV.setText(maghrib); 
ishaTV.setText(isha); 
} 

in OnPostExecute() von GetMethodEx().