custom Adapter getView gives NullPointException

Question

I have a listView which need a customized adapter- Dict_Adapter. One of the constructor of Dict_Adapter is:

public Dict_Adapter(Context c,ArrayList<String> Meanings){
    context=c;
    meaning=Meanings;
    type=2;
}

In getView of the adapter, the app will set two TextView and one ImageView like below:

 @Override
public View getView(int i, View view, ViewGroup viewGroup) {
    if (view==null) {
        LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        view = inflater.inflate(R.layout.dict_listview_items, null);
    }
    TextView Difficulty=(TextView) view.findViewById(R.id.Dict_ListView_Difficulty);
    TextView Word=(TextView) view.findViewById(R.id.Dict_ListView_Word);
    ImageView Arrow=(ImageView) view.findViewById(R.id.Dict_ListView_Arrow);
    if (type==2){
        Difficulty.setText(difficulty.get(i));
        Word.setText(meaning.get(i));
        Arrow.setVisibility(View.INVISIBLE);
    }
    return view;

Difficulty and Word is two ArrayLists that supplies contents to the TextViews.

In the Activity Daily_Word.java, Dict_Adapter will be applied below:

ListView Daily_Word_Meaning_List=(ListView) findViewById(R.id.Daily_Word_Meaning_List);
    String sourceMeaning=c.getString(1);
    Log.w("SourceMeaning",sourceMeaning);
    ArrayList<String> meaningList=new ArrayList<>(Arrays.asList(sourceMeaning.split("&")));
    for (int i=0; i<meaningList.size();i++){
        Log.w("Meaning",meaningList.get(i));
    }
    Dict_Adapter adapter1=new Dict_Adapter(getBaseContext(),meaningList);
    Daily_Word_Meaning_List.setAdapter(adapter1);

Then here comes a problem: the app throws NullPointerException:

07-06 23:01:38.513 341-341/com.android.luftschlafer.wordenhancement E/AndroidRuntime: FATAL EXCEPTION: main
                                                                                  java.lang.NullPointerException
                                                                                      at com.android.luftschlafer.wordenhancement.Adapters.Dict_Adapter.getView(Dict_Adapter.java:103)

Which means Difficulty.setText(difficulty.get(i)); gives nullpointerexception.

How to overcome this problem? I have already deployed the layout and widgets in "dict_listview_items" already.