java - 不兼容的类型 : cannot be converted to Context

Question

我正在尝试进行“动态搜索”..

这个 fragment 是我实现请求的地方...这里我收到错误(错误:(95, 40)错误:不兼容的类型:无法转换为上下文)和 MySingleton.getInstance(this).addToRequestQueue(jsObjRequest) ;这是我收到错误的行

fragment :

public class CercaFragment extends Fragment {

TextView textView;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup parent, Bundle savedInstanceState) {

    View v = inflater.inflate(R.layout.cerca, parent, false);


    textView = (TextView) v.findViewById(R.id.textView);
    setHasOptionsMenu(true);

    EditText search = (EditText)v.findViewById(R.id.editText);

    search.addTextChangedListener(new TextWatcher() {

        @Override
        public void beforeTextChanged(CharSequence s, int start, int count, int after) {                // TODO Auto-generated method stub            }

        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {                
            textView.setText(s);

            String url = "http://api.geonames.org/searchJSON?q=londoz&maxRows=10&fuzzy=0.8&username=demo";

            JsonObjectRequest jsObjRequest = new JsonObjectRequest
                    (Request.Method.GET, url, null, new Response.Listener<JSONObject>() {

                        @Override
                        public void onResponse(JSONObject response) {


                            GeonamesClass example = new Gson().fromJson(response.toString(),GeonamesClass.class);
                                                            textView.setText("Name"+example.getUsers().get(0).getName());
                        }
                    }, new Response.ErrorListener() {

                        @Override
                        public void onErrorResponse(VolleyError error) {
                            // TODO Auto-generated method stub

                        }
                    });
            // Access the RequestQueue through your singleton class.

           MySingleton.getInstance(this).addToRequestQueue(jsObjRequest);

        }

        @Override
        public void afterTextChanged(Editable s) {

        }

    });

    return v;

}
}

MySingleton:

public class MySingleton {
    private static MySingleton mInstance;
    private RequestQueue mRequestQueue;
    private ImageLoader mImageLoader;
    private static Context mCtx;

private MySingleton(Context context) {
    mCtx = context;
    mRequestQueue = getRequestQueue();

    mImageLoader = new ImageLoader(mRequestQueue,
            new ImageLoader.ImageCache() {
                private final LruCache<String, Bitmap>
                        cache = new LruCache<String, Bitmap>(20);

                @Override
                public Bitmap getBitmap(String url) {
                    return cache.get(url);
                }

                @Override
                public void putBitmap(String url, Bitmap bitmap) {
                    cache.put(url, bitmap);
                }
            });
}

public static synchronized MySingleton getInstance(Context context) {
    if (mInstance == null) {
        mInstance = new MySingleton(context);
    }
    return mInstance;
}

public RequestQueue getRequestQueue() {
    if (mRequestQueue == null) {
        // getApplicationContext() is key, it keeps you from leaking the
        // Activity or BroadcastReceiver if someone passes one in.
        mRequestQueue = Volley.newRequestQueue(mCtx.getApplicationContext());
    }
    return mRequestQueue;
}

public <T> void addToRequestQueue(Request<T> req) {
    getRequestQueue().add(req);
}

public ImageLoader getImageLoader() {
    return mImageLoader;
}

}

Answer 1

当您在事件中执行这个时，您并不是引用应用程序的上下文，而是引用生成事件的对象，以获取上下文你的单例你必须在事件之外执行 MySingleton.Getinstance(this)... ，或者如果它在你想调用它的内部，则执行类似 MySingleton.Getinstance.(getActivity ()) .......

getActivity():是在 fragment 中调用的方法，以调用其上下文引用

希望有帮助一句问候