使用Hilt框架

app/src/main/java/com/navinfo/volvo/util/LiveDataUtils.kt

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+package com.navinfo.volvo.util
+
+import androidx.lifecycle.LifecycleOwner
+import androidx.lifecycle.LiveData
+import androidx.lifecycle.MutableLiveData
+import androidx.lifecycle.Observer
+
+
+/**
+ * This functions helps in transforming a [MutableLiveData] of type [T]
+ * to a [LiveData] of type [T]
+ */
+fun <T> MutableLiveData<T>.asLiveData() = this as LiveData<T>
+
+/**
+ * This function helps to observe a [LiveData] once
+ */
+fun <T> LiveData<T>.observeOnce(lifecycleOwner: LifecycleOwner, observer: Observer<T>) {
+    observe(
+        lifecycleOwner,
+        object : Observer<T> {
+            override fun onChanged(t: T?) {
+                observer.onChanged(t)
+                removeObserver(this)
+            }
+        }
+    )
+}

app/src/main/java/com/navinfo/volvo/util/NetResult.kt

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+package com.navinfo.volvo.util
+
+/**
+ * Created by Mayokun Adeniyi on 23/05/2020.
+ */
+
+/**
+ * A generic class that holds a value with its loading status.
+ * @param <T>
+ */
+sealed class NetResult<out R> {
+
+    data class Success<out T>(val data: T?) : NetResult<T>()
+    data class Error(val exception: Exception) : NetResult<Nothing>()
+    object Loading : NetResult<Nothing>()
+
+    override fun toString(): String {
+        return when (this) {
+            is Success<*> -> "Success[data=$data]"
+            is Error -> "Error[exception=$exception]"
+            is Loading -> "Loading"
+        }
+    }
+}

app/src/main/java/com/navinfo/volvo/util/SharedPreferenceHelper.kt

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+package com.navinfo.volvo.util
+
+import android.content.Context
+import android.content.SharedPreferences
+import android.preference.PreferenceManager
+import androidx.core.content.edit
+import com.google.gson.Gson
+
+
+class SharedPreferenceHelper {
+
+    companion object {
+
+        private const val WEATHER_PREF_TIME = "Weather pref time"
+        private const val WEATHER_FORECAST_PREF_TIME = "Forecast pref time"
+        private const val CITY_ID = "City ID"
+        private var prefs: SharedPreferences? = null
+        private const val LOCATION = "LOCATION"
+
+        @Volatile
+        private var instance: SharedPreferenceHelper? = null
+
+        /**
+         * This checks if there is an existing instance of the [SharedPreferences] in the
+         * specified [context] and creates one if there isn't or else, it returns the
+         * already existing instance. This function ensures that the [SharedPreferences] is
+         * accessed at any instance by a single thread.
+         */
+        fun getInstance(context: Context): SharedPreferenceHelper {
+            synchronized(this) {
+                val _instance = instance
+                if (_instance == null) {
+                    prefs = PreferenceManager.getDefaultSharedPreferences(context)
+                    instance = _instance
+                }
+                return SharedPreferenceHelper()
+            }
+        }
+    }
+
+    /**
+     * This function saves the initial time [System.nanoTime] at which the weather information
+     * at the user's location is accessed.
+     * @param time the value of [System.nanoTime] when the weather information is received.
+     */
+    fun saveTimeOfInitialWeatherFetch(time: Long) {
+        prefs?.edit(commit = true) {
+            putLong(WEATHER_PREF_TIME, time)
+        }
+    }
+
+    /**
+     * This function returns the saved value of [System.nanoTime] when the weather information
+     * at the user's location was accessed.
+     * @see saveTimeOfInitialWeatherFetch
+     */
+    fun getTimeOfInitialWeatherFetch() = prefs?.getLong(WEATHER_PREF_TIME, 0L)
+
+    /**
+     * This function saves the initial time [System.nanoTime] at which the weather forecast
+     * at the user's location is accessed.
+     * @param time the value of [System.nanoTime] when the weather forecast is received.
+     */
+    fun saveTimeOfInitialWeatherForecastFetch(time: Long) {
+        prefs?.edit(commit = true) {
+            putLong(WEATHER_FORECAST_PREF_TIME, time)
+        }
+    }
+
+    /**
+     * This function returns the saved value of [System.nanoTime] when the weather forecast
+     * at the user's location was accessed.
+     * @see saveTimeOfInitialWeatherForecastFetch
+     */
+    fun getTimeOfInitialWeatherForecastFetch() = prefs?.getLong(WEATHER_FORECAST_PREF_TIME, 0L)
+
+    /**
+     * This function saves the [cityId] of the location whose weather information has been
+     * received.
+     * @param cityId the id of the location whose weather has been received
+     */
+    fun saveCityId(cityId: Int) {
+        prefs?.edit(commit = true) {
+            putInt(CITY_ID, cityId)
+        }
+    }
+
+    /**
+     * This function returns the id of the location whose weather information has been received.
+     * @see saveCityId
+     */
+    fun getCityId() = prefs?.getInt(CITY_ID, 0)
+
+    /**
+     * This function gets the value of the cache duration the user set in the
+     * Settings Fragment.
+     */
+    fun getUserSetCacheDuration() = prefs?.getString("cache_key", "0")
+
+    /**
+     * This function gets the value of the app theme the user set in the
+     * Settings Fragment.
+     */
+    fun getSelectedThemePref() = prefs?.getString("theme_key", "")
+
+    /**
+     * This function gets the value of the temperature unit the user set in the
+     * Settings Fragment.
+     */
+    fun getSelectedTemperatureUnit() = prefs?.getString("unit_key", "")
+
+//    /**
+//     * This function saves a [LocationModel]
+//     */
+//    fun saveLocation(location: LocationModel) {
+//        prefs?.edit(commit = true) {
+//            val gson = Gson()
+//            val json = gson.toJson(location)
+//            putString(LOCATION, json)
+//        }
+//    }
+
+//    /**
+//     * This function gets the value of the saved [LocationModel]
+//     */
+//    fun getLocation(): LocationModel {
+//        val gson = Gson()
+//        val json = prefs?.getString(LOCATION, null)
+//        return gson.fromJson(json, LocationModel::class.java)
+//    }
+}