graph TD
A[启动应用] --> B[加载 Room 数据库中的城市]
B --> C{是否有城市数据}
C -- 是 --> D[请求天气 API 获取天气数据]
C -- 否 --> E[提示用户添加城市]
D --> F[解析并展示天气数据]
E --> G[用户添加城市]
G --> D
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// MainActivity.java
public class MainActivity extends AppCompatActivity {
    private WeatherViewModel weatherViewModel;
    private RecyclerView recyclerView;
    private CityListAdapter cityListAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        recyclerView = findViewById(R.id.recycler_view);
        cityListAdapter = new CityListAdapter(this);
        recyclerView.setAdapter(cityListAdapter);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));

        weatherViewModel = new ViewModelProvider(this).get(WeatherViewModel.class);
        weatherViewModel.getAllCities().observe(this, cities -> {
            cityListAdapter.setCities(cities);
            fetchWeatherData(cities);
        });
    }

    private void fetchWeatherData(List<City> cities) {
        for (City city : cities) {
            // 调用天气API获取数据
            String url = "https://api.weather.com/v3/wx/conditions/current?apiKey=YOUR_API_KEY&format=json&language=en-US&location=" + city.getLatitude() + "," + city.getLongitude();
            JsonObjectRequest jsonObjectRequest = new JsonObjectRequest(Request.Method.GET, url, null,
                    response -> {
                        try {
                            double temperature = response.getJSONObject("temperature").getDouble("value");
                            double humidity = response.getJSONObject("humidity").getDouble("value");
                            double windSpeed = response.getJSONObject("windSpeed").getDouble("value");
                            weatherViewModel.updateWeatherData(city.getId(), temperature, humidity, windSpeed);
                        } catch (JSONException e) {
                            e.printStackTrace();
                        }
                    },
                    error -> error.printStackTrace());

            RequestQueue queue = Volley.newRequestQueue(this);
            queue.add(jsonObjectRequest);
        }
    }
}
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// WeatherViewModelTest.java
public class WeatherViewModelTest {
    private WeatherViewModel weatherViewModel;
    private CityDao mockCityDao;

    @Before
    public void setUp() {
        mockCityDao = mock(CityDao.class);
        weatherViewModel = new WeatherViewModel(mockCityDao);
    }

    @Test
    public void testAddCity() {
        City city = new City("Shanghai", 31.23, 121.47);
        weatherViewModel.insert(city);
        verify(mockCityDao).insert(city);
    }

    @Test
    public void testGetAllCities() {
        List<City> cities = Arrays.asList(new City("Beijing", 39.91, 116.40));
        when(mockCityDao.getAllCities()).thenReturn(cities);
        
        LiveData<List<City>> result = weatherViewModel.getAllCities();
        assertEquals(cities, result.getValue());
    }
}
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