java - 如何修复 java.lang.ClassCastException...无法强制转换接口(interface)

Question

在我的主要 Activity 中，我有一个显示天气信息的 fragment 。我在 fragment 和主 Activity 之间有一个接口(interface)，将数据从 fragment 发送到 Activity 。问题是当尝试专门输入 fragment Activity 时，应用程序崩溃并显示此错误。

任何帮助或任何替代方法将不胜感激。

    private void loadData() {
        final List<WeatherForeCast> listWeatherForeCasts = new ArrayList<>();
        StringRequest stringRequest = new StringRequest(Request.Method.GET,
                "https://www.metaweather.com/api/location/3534/",
                new Response.Listener<String>() {
                    @Override
                    public void onResponse(String response) {
                        try {
                            JSONObject jsonObject = new JSONObject(response);
                            JSONArray array = jsonObject.getJSONArray("consolidated_weather");
                            JSONObject jsonObject1 = jsonObject.getJSONObject("parent");
                            String cityCountry = jsonObject1.getString("title");
                            cityCountry = cityCountry + " ," + jsonObject.getString("title");
                            textViewCity.setText(Html.fromHtml(cityCountry ));

                            for (int x = 0; x < 6; x++) {
                                JSONObject weatherObject = array.getJSONObject(x);
                                WeatherForeCast weatherForeCast = new WeatherForeCast(
                                        weatherObject.getInt("air_pressure"),
                                        weatherObject.getInt("wind_speed"),
                                        weatherObject.getInt("the_temp"),
                                        weatherObject.getInt("humidity"),
                                        weatherObject.getString("weather_state_name"),
                                        weatherObject.getString("applicable_date"));
                                listWeatherForeCasts.add(weatherForeCast);
                                weatherState = listWeatherForeCasts.get(0).getWeatherState();
                                if(x == 0) {
                                    sendData();
                                }
                            }
                            ;
                            adapter = new Adapter(listWeatherForeCasts, getActivity());
                            recyclerView.setAdapter(adapter);

                        } catch (JSONException e) {
                            e.printStackTrace();
                        }
                    }
                },
                new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        Toast.makeText(getActivity(), error.getMessage(), Toast.LENGTH_SHORT).show();
                    }
                });
        RequestQueue requestQueue = Volley.newRequestQueue(getActivity());
        requestQueue.add(stringRequest);

    }




    public void sendData()
    {
        Log.i("fault", weatherState);
        getFirstWeatherInterface getFirstWeather = (getFirstWeatherInterface) getActivity();
        getFirstWeather.getFirst(weatherState);

    }

//Interface is implemented in the Activity
    @Override
    public WeatherForeCast getFirst(String string) {

        Log.i("fault2", string);
        return null
}

java.lang.ClassCastException: com.fan4.outdoorplus.WeatherFragments.WeatherActivity cannot be cast to com.fan4.outdoorplus.getFirstWeatherInterface
        at com.fan4.outdoorplus.WeatherFragments.WeatherFragment.sendData(WeatherFragment.java:143)
        at com.fan4.outdoorplus.WeatherFragments.WeatherFragment$1.onResponse(WeatherFragment.java:117)
        at com.fan4.outdoorplus.WeatherFragments.WeatherFragment$1.onResponse(WeatherFragment.java:92)
        at com.android.volley.toolbox.StringRequest.deliverResponse(StringRequest.java:82)
        at com.android.volley.toolbox.StringRequest.deliverResponse(StringRequest.java:29)
        at com.android.volley.ExecutorDelivery$ResponseDeliveryRunnable.run(ExecutorDelivery.java:102)
        at android.os.Handler.handleCallback(Handler.java:873)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:193)
        at android.app.ActivityThread.main(ActivityThread.java:6669)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)

Answer 1

你的问题就在这一行。您正在尝试将 activity 转换为 getFirstWeatherInterface

getFirstWeatherInterface getFirstWeather = (getFirstWeatherInterface) getActivity();