Question

我正在做一个android项目，尝试使用片段

我的一个片段有一个微调器，为此我需要一个单独的侦听器

当我设置侦听器时，由于需要此对象，因此将一个对象发送给构造函数，但我不知道为什么在片段中调用它而在侦听器中对其进行更新时，总会得到null

也许我必须使用另一种方式来传递对象，但是我没有找到任何

如果您能帮助我知道为什么[chosenTrackable]在片段中始终为null，将不胜感激。以及是否有更好的方法在片段和侦听器之间调用对象

这是我的代码：

public class AddTracking extends Fragment {
    Spinner trackableSpinner;
    Context context;
    HashMap <Integer, MyTrackable> myTrackables ;
    MyTrackable chosenTrackable;
    private static final String TAG = "AddTracking";

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

        context = container.getContext();
        View view = inflater.inflate(R.layout.fragment_add_tracking, container, false);

        myTrackables= new Model(view.getContext()).getTrackables();

        //initilizing
        trackableSpinner =   view.findViewById(R.id.trackable_spinner);

        //setup trackable spinner
        ArrayAdapter trackableSpinnerAdapter = new ArrayAdapter(this.getActivity(),
                android.R.layout.simple_spinner_item, new ArrayList<>(myTrackables.values()));
        trackableSpinnerAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        trackableSpinner.setAdapter(trackableSpinnerAdapter);
        trackableSpinner.setOnItemSelectedListener( new SpinnerTrackableItemSelectedListener(this.getActivity(),chosenTrackable));




        chosenTrackable = myTrackables.get(trackableSpinner.getSelectedItemPosition());
        Log.d(TAG, "onCreateView:  " + chosenTrackable);
         return view;
    }
}

收听者：

public class SpinnerTrackableItemSelectedListener implements AdapterView.OnItemSelectedListener {
Context  context ;
private static final String TAG = "SpinnerTrackableItemSel";
MyTrackable chosenTrackable;

public SpinnerTrackableItemSelectedListener(Context context, MyTrackable chosenTrackable) {
    this.context = context;
    this.chosenTrackable = chosenTrackable ;
}

@Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
    chosenTrackable = (MyTrackable) parent.getAdapter().getItem(position);
 Log.d(TAG, "loadTimeSpinner: " + chosenTrackable);

}

@Override
public void onNothingSelected(AdapterView<?> parent) {

}




}

片段中未更新对象

0 个答案: