Question

I want to run an instance of fragment from activity. But it returns error null object reference.

 java.lang.NullPointerException: Attempt to invoke virtual method 'void com.mani.view.StaggeredGridView.addItem(com.mani.view.StaggeredGridViewItem)' on a null object reference
 at com.example.myapp.FavouriteListFragment.onCreateView(FavouriteListFragment.java:57)

When i debug, this line shows null pointer error

  mStaggeredView.addItem(item);

debug result shows that fragmentClass is null value. It does not works well now after I have added inheritance class in my fragment. Here is my fragment

    public class FavouriteListFragment extends Fragment {

    public static final String ARG_ITEM_ID = "favorite_list";
    private SharedPreference sharedPreference;
    private StaggeredGridView mStaggeredView;
    TextView tv;
    ImageView iv;
    String text;
    String favouriteUrl;

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

        iv=(ImageView)rootView.findViewById(R.id.imageView);
        text = sharedPreference.getValue(getActivity());

        sharedPreference.saveFavourite(getActivity(), text);

        String[] photoUrl;
        photoUrl = new String[10];

        for (int index = 0; index < photoUrl.length; index++) {

            photoUrl[index]=text;
            StaggeredGridViewItem item = null;
            item = new FavouriteGridItem(getActivity(),photoUrl); //pass one image of index
            mStaggeredView.addItem(item);
        }

        URL url = null;
        try {
            url = new URL(text);
        } catch (MalformedURLException e) {
            e.printStackTrace();
        }
        Bitmap bmp = null;
        try {
            bmp = BitmapFactory.decodeStream(url.openConnection().getInputStream());
        } catch (IOException e) {
            e.printStackTrace();
        }
        iv.setImageBitmap(bmp);
        return rootView;

    }
}

Answer 1

这一行是你的一个问题：

mStaggeredView.addItem(item);

根据您发布的代码，您在mStaggeredView.addItem()上获得nullpointer是合乎逻辑的，因为您没有为mStaggeredView分配任何内容。您必须在某处{/ 1}}执行某些操作

null object reference on fragment new instance

1 个答案: