java - 在 fragment 中使用网络 ImageView - android studio

Question

我正在尝试使用 volley 库下载 fragment 中的图像。但我无法修复错误:

public static class ViewFragment extends Fragment {

        ImageLoader mImageLoader;
        NetworkImageView mNetworkImageView;
        private static String IMAGE_URL =
                "http://meteo.profi-net.sk/webcams/BIELAPUT-l.jpg";

        public ViewFragment() {
            // Required empty public constructor
        }

        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);

            // Get the NetworkImageView that will display the image.
            mNetworkImageView = (NetworkImageView) getView().findViewById(R.id.networkImageView);

            // Get the ImageLoader through your singleton class.
            mImageLoader = VolleySingleton.getInstance(this).getImageLoader();  //!!!!!! HERE IS THE ERROR

            // Set the URL of the image that should be loaded into this view, and
            // specify the ImageLoader that will be used to make the request.
            mNetworkImageView.setImageUrl(IMAGE_URL, mImageLoader);

        }

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


    }

getInstance(this) 被标记为错误，但我不知道如何更改它。如果我在某些 Activity 中编写完全相同的代码，它就会起作用。

有人可以解释一下如何在 fragment 中使用 NetworkImageView 吗？

Answer 1

getInstance 需要一个 Context 作为参数，Fragment 不是，但 Activity 是。Fragment可以通过调用getActivity方法来访问其持有的Activity。您应该在每次调用之前检查 fragment 是否仍附加到其 Activity ，否则您将崩溃

所以你可以这样做:

if(isAdded())
{
            .......... your code ..............
            // Get the ImageLoader through your singleton class.
            mImageLoader = VolleySingleton.getInstance(getActivity()).getImageLoader();
                .......... your code ..............
}