刷新面板在未被搜索到城市时永久重新加载

Question

我在天气应用程序上设置了一个滑动刷新面板，以便在我向下滑动刷新按钮时更新从API接收到的天气数据。当一个城市被搜索时，这个功能可以很好地工作，但现在的问题是，如果我在刷新面板之前还没有搜索任何城市，它会永远重新加载，直到我退出应用程序阻碍应用程序进程，我的应用程序被设计成不保存以前的天气数据，直到用户再次搜索一个城市。

我想要么完全停止刷新面板重新加载，直到一个城市被搜索，或者只是限制重新加载所需的时间，直到一个城市被搜索。请问我该怎么做?我检查了这个网站类似的问题/答案，发现没有一个帮助/与我想要实现的目标有关。

这是当前刷新面板的编程设置:

realSwipe.setOnRefreshListener(() -> {
// perform the delay action
new Handler().postDelayed(() -> {
// this code is for stop refreshing icon, After 1000 ms automatically refresh icon will stop
realSwipe.setRefreshing(false);
}, 1000);
});

下面是我的片段代码(以防需要):

public class FirstFragment extends Fragment {
private WeatherDataViewModel viewModel;
public FirstFragment() {
// Required empty public constructor
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View rootView = inflater.inflate(R.layout.fragment_first, container, false);
// For displaying weather data
final TextView current_temp = rootView.findViewById(R.id.textView10);
final TextView current_output = rootView.findViewById(R.id.textView11);
final TextView rise_time = rootView.findViewById(R.id.textView25);
final TextView set_time = rootView.findViewById(R.id.textView26);
final TextView temp_out = rootView.findViewById(R.id.textView28);
final TextView Press_out = rootView.findViewById(R.id.textView29);
final TextView Humid_out = rootView.findViewById(R.id.textView30);
final TextView Ws_out = rootView.findViewById(R.id.textView33);
final TextView Visi_out = rootView.findViewById(R.id.textView34);
final TextView Cloud_out = rootView.findViewById(R.id.textView35);
final ImageView current_icon = rootView.findViewById(R.id.imageView6);
final SwipeRefreshLayout realSwipe = rootView.findViewById(R.id.real_swipe);
// Get our ViewModel instance
viewModel = new ViewModelProvider(requireActivity()).get(WeatherDataViewModel.class);
// And whenever the data changes, refresh the UI
viewModel.getWeatherDataLiveData().observe(getViewLifecycleOwner(), data -> {
realSwipe.setOnRefreshListener(() -> {
// perform the delay action
new Handler().postDelayed(() -> {
// this code is for stop refreshing icon, After 1000 ms automatically refresh icon will stop
realSwipe.setRefreshing(false);
}, 1000);
});
int drawableResource = -1; // here define default icon for example R.drawable.default_weather_icon
int soundResource = -1; // Default sound is nothing
if (data != null) {
current_temp.setVisibility(View.VISIBLE);
current_temp.setText(data.getMain().getTemp() + " ℃"); // for that you can use strings resource and templates more in https://developer.android.com/guide/topics/resources/string-resource.html#formatting-strings
current_output.setVisibility(View.VISIBLE);
current_output.setText(data.getWeather().get(0).getDescription());
rise_time.setVisibility(View.VISIBLE);
rise_time.setText(data.getSys().getSunrise() + " ");
set_time.setVisibility(View.VISIBLE);
set_time.setText(data.getSys().getSunset() + " ");
temp_out.setVisibility(View.VISIBLE);
temp_out.setText(data.getMain().getTemp() + " ℃");
Press_out.setVisibility(View.VISIBLE);
Press_out.setText(data.getMain().getPressure() + " hpa");
Humid_out.setVisibility(View.VISIBLE);
Humid_out.setText(data.getMain().getHumidity() + " %");
Ws_out.setVisibility(View.VISIBLE);
Ws_out.setText(data.getWind().getSpeed() + " Km/h");
Visi_out.setVisibility(View.VISIBLE);
Visi_out.setText(data.getVisibility() + " m");
Cloud_out.setVisibility(View.VISIBLE);
Cloud_out.setText(data.getClouds().getAll() + " %");
// get actual weather.
String icon = data.getWeather().get(0).getIcon();
switch (icon) {
case "01d":
case "01n":
drawableResource = R.drawable.sun;
soundResource = R.raw.clear_sky_sound;
break;
case "02d":
case "021n":
drawableResource = R.drawable.few_clouds;
soundResource = R.raw.clouds_sound;
break;
case "03d":
case "03n":
drawableResource = R.drawable.scattered_clouds;
soundResource = R.raw.clouds_sound;
break;
case "04d":
case "04n":
drawableResource = R.drawable.broken_clouds;
soundResource = R.raw.clouds_sound;
break;
case "09d":
case "09n":
drawableResource = R.drawable.shower_rain;
soundResource = R.raw.shower_rain_sound;
break;
case "10d":
case "10n":
drawableResource = R.drawable.small_rain;
soundResource = R.raw.shower_rain_sound;
break;
case "11d":
case "11n":
drawableResource = R.drawable.thunderstorm;
soundResource = R.raw.thunderstorm_sound;
break;
case "13d":
case "13n":
drawableResource = R.drawable.snow;
soundResource = R.raw.snow_sound;
break;
case "50d":
case "50n":
drawableResource = R.drawable.mist;
soundResource = R.raw.mist_sound;
break;
}
if (drawableResource != -1)
current_icon.setImageResource(drawableResource);
// set the first host instance for displaying the weather icons
if (soundResource != -1 && viewModel.soundResource != soundResource) {
viewModel.soundResource = soundResource;
if (viewModel.getMediaPlayer() != null) {
// we set our soundplayer in retrospect to our viewmodel
// stop the playing
if (viewModel.getMediaPlayer().isPlaying()) {
viewModel.getMediaPlayer().stop();
}
// release mMediaPlayer resoruces
viewModel.getMediaPlayer().release();
viewModel.setMediaPlayer(null);
}
// Play the new resource
viewModel.prepareMediaPlayer(requireContext(), soundResource);
}
} else {
Log.e("TAG", "No City found");
current_temp.setVisibility(View.GONE);
current_output.setVisibility(View.GONE);
rise_time.setVisibility(View.GONE);
set_time.setVisibility(View.GONE);
temp_out.setVisibility(View.GONE);
Press_out.setVisibility(View.GONE);
Humid_out.setVisibility(View.GONE);
Ws_out.setVisibility(View.GONE);
Visi_out.setVisibility(View.GONE);
Cloud_out.setVisibility(View.GONE);
Toast.makeText(requireActivity(), "No City found", Toast.LENGTH_SHORT).show();
}
});
return rootView;
}
public void getWeatherData(String name) {
// The ViewModel controls loading the data, so we just
// tell it what the new name is - this kicks off loading
// the data, which will automatically call through to
// our observe() call when the data load completes
viewModel.setCityName(name);
}
}

Answer 1

现在的问题是，如果我还没有搜索任何城市之前滑动刷新面板，它会永远重新加载

因此，每当搜索的城市是空白/空字符串时，就会出现问题。这意味着在这种情况下会触发观察到的MutuableLiveData回调。

因为我参与了你上一个问题;加载没有空字符串检查的数据:

private void loadData() {
// Get the last name that was set
String name = state.get("name");
// Now kick off a load from the server
ApiInterface apiInterface = ApiClient.getClient().create(ApiInterface.class);
Call<Example> call = apiInterface.getWeatherData(name);
call.enqueue(new Callback<Example>() {
@Override
public void onResponse(@NonNull Call<Example> call, @NonNull Response<Example> response) {
// Save the response we've gotten
// This will automatically update our UI
mutableWeatherData.setValue(response.body());
}
@Override
public void onFailure(@NotNull Call<Example> call, @NotNull Throwable t) {
t.printStackTrace();
}
});
}

修改:

• 如果城市名称为空，则提前返回
• 检查在更新UI之前是否没有API Retrofit的响应

private void loadData() {
// Get the last name that was set
String name = state.get("name");

// Return early if the city name is empty
if (name == null || name.isEmpty()) return;
// Now kick off a load from the server
ApiInterface apiInterface = ApiClient.getClient().create(ApiInterface.class);
Call<Example> call = apiInterface.getWeatherData(name);
call.enqueue(new Callback<Example>() {
@Override
public void onResponse(@NonNull Call<Example> call, @NonNull Response<Example> response) {

// Check if there is no response from the the Retrofit before updating the UI
if (response.body() == null) return;

// Save the response we've gotten
// This will automatically update our UI
mutableWeatherData.setValue(response.body());
}
@Override
public void onFailure(@NotNull Call<Example> call, @NotNull Throwable t) {
t.printStackTrace();
}
});
}

更新正如评论和聊天中指出的那样，期望的行为不是定期更新UI，而是让用户从顶部滑动屏幕来更新UI。

要解决swipeToRefresh重新加载问题，需要将swipeToRefresh侦听器从LiveData观察中取出:

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {

// Code is omitted  ....                 

realSwipe.setOnRefreshListener(() -> {
// perform the delay action
new Handler().postDelayed(() -> {
// this code is for stop refreshing icon, After 1000 ms automatically refresh icon will stop
realSwipe.setRefreshing(false);
}, 1000);
});
// And whenever the data changes, refresh the UI
viewModel.getWeatherDataLiveData().observe(getViewLifecycleOwner(), data -> {
int drawableResource = -1; // here define default icon for example R.drawable.default_weather_icon
int soundResource = -1; // Default sound is nothing

// Rest of the code ....