Question

我试图在片段中填充我的列表，但它返回空对象引用。（Function2）有我的代码：

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

Answer 1

您需要将需要视图的内容移动到onCreateView：

public void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);

    person.add(new Gender("35AE111", false, "60 km/h"));
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    View view = inflater.inflate(R.layout.fragment_all_vehicles, container, false);
    final ListView listview= (ListView)view.findViewById(R.id.liste);

    CustomAdapter customAdapter=new CustomAdapter(getActivity(), kisiler);
    listview.setAdapter(customAdapter);
    return view;
}

Answer 2

问题是Fragment方法中尚未创建onCreate的视图。您应该将代码从onCreate移至onCreateView：

    @Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    View view = inflater.inflate(R.layout.fragment_all_vehicles, container, false);

    final ListView listview= (ListView)view.findViewById(R.id.liste);

    CustomAdapter customAdapter=new CustomAdapter(getActivity(), kisiler);
    listview.setAdapter(customAdapter);

    return view;
}

Answer 3

由于您在findviewbyid(int)中呼叫onCreate()并在onCreateView()中充气布局而引起的异常....！

问题是片段的onCreate()方法首先调用，之后片段生命周期调用onCreateView ......！

您应该阅读fragment's life cycle

下面的代码可以帮助您，

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View view = inflater.inflate(R.layout.fragment_all_vehicles, container, false);
        person.add(new Gender("35AE111", false, "60 km/h"));

        final ListView listview= (ListView)view.findViewById(R.id.liste);

        CustomAdapter customAdapter=new CustomAdapter(getActivity(), kisiler);
        listview.setAdapter(customAdapter);
return view;
    }
    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
}

Answer 4

由于在onCreateView（）之前调用onCreate（）并且onCreate中的getView（）返回null，因此发生了null ptr异常。试试下面的代码片段。我已将onCreate（）中的代码移动到onCreateView（）

public void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);


}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    View view = inflater.inflate(R.layout.fragment_all_vehicles, container, false);
    person.add(new Gender("35AE111", false, "60 km/h"));

    final ListView listview= (ListView)getView().findViewById(R.id.liste);

    CustomAdapter customAdapter=new CustomAdapter(getActivity(), kisiler);
    listview.setAdapter(customAdapter);
    return view;
}

Answer 5

要确保您的观看次要曝光，您可以覆盖onViewCreated

@Override
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);
    person.add(new Gender("35AE111", false, "60 km/h"));

    final ListView listview= (ListView) view.findViewById(R.id.liste);

    CustomAdapter customAdapter = new CustomAdapter(getActivity(), kisiler);
    listview.setAdapter(customAdapter);
}

还要确保XML中的listview id正确，有时这是一个问题。

如何填充片段活动中的列表视图？

5 个答案: