gistfile1.txt

val lastSyncTime = prefs.asLiveData(PREFKEY_LAST_SYNC_TIME, 0L)

SharedPreferenceLiveData

import android.content.SharedPreferences
import android.content.SharedPreferences.OnSharedPreferenceChangeListener
import androidx.lifecycle.LiveData

class SharedPreferenceLiveData<T>(
        val prefs: SharedPreferences,
        val key: String,
        val defaultValue: T,
        val valueProvider: (prefs: SharedPreferences, key: String, defValue: T?) -> T?
) : LiveData<T>() {

    private val onChangeListener = OnSharedPreferenceChangeListener { sharedPrefs, key ->
        if (key == this.key) value = valueProvider(sharedPrefs, key, defaultValue)
    }

    override fun onActive() {
        super.onActive()
        value = valueProvider(prefs, key, defaultValue)
        prefs.registerOnSharedPreferenceChangeListener(onChangeListener)
    }

    override fun onInactive() {
        prefs.unregisterOnSharedPreferenceChangeListener(onChangeListener)
        super.onInactive()
    }
}

inline fun <reified T : Any> SharedPreferences.asLiveData(key: String, defaultValue: T?): LiveData<T?> =
        SharedPreferenceLiveData(this, key, defaultValue, getValueProvider(T::class))

@Suppress("UNCHECKED_CAST")
fun <T : Any> getValueProvider(clazz: KClass<T>): ((prefs: SharedPreferences, key: String, defValue: T?) -> T?) =
        when (clazz) {
            String::class -> { pref, key, defValue -> pref.getString(key, defValue as? String) as T? }
            Boolean::class -> { pref, key, defValue -> pref.getBoolean(key, true == defValue) as T? }
            Int::class -> { pref, key, defValue -> pref.getInt(key, defValue as? Int ?: 0) as T? }
            Long::class -> { pref, key, defValue -> pref.getLong(key, defValue as? Long ?: 0L) as T? }
            Float::class -> { pref, key, defValue -> pref.getFloat(key, defValue as? Float ?: 0f) as T? }
            else -> throw UnsupportedOperationException("Type $clazz is not supported!")
        }