android - LiveData with shared preferences

Question

I have a settings screen where I am setting some values. When I set those values it gets saved in shared preferences and these values are needed in my request to the network api call as parameters.

Now I can use a listener for shared preferences in my activity then make an api call and get fresh data, but I want to use this with LiveData.

How can I listen for changes in the shared preferences using LiveData and then make the network call using the new parameters.

Answer 1

The following awesome piece of code is LiveData Implementation of SharedPreference. It works perfectly.

package com.chargingwatts.chargingalarm.util.preference;

import android.arch.lifecycle.LiveData
import android.content.SharedPreferences

abstract class SharedPreferenceLiveData<T>(val sharedPrefs: SharedPreferences,
                                           val key: String,
                                           val defValue: T) : LiveData<T>() {

    private val preferenceChangeListener = SharedPreferences.OnSharedPreferenceChangeListener { sharedPreferences, key ->
        if (key == this.key) {
            value = getValueFromPreferences(key, defValue)
        }
    }

    abstract fun getValueFromPreferences(key: String, defValue: T): T

    override fun onActive() {
        super.onActive()
        value = getValueFromPreferences(key, defValue)
        sharedPrefs.registerOnSharedPreferenceChangeListener(preferenceChangeListener)
    }

    override fun onInactive() {
        sharedPrefs.unregisterOnSharedPreferenceChangeListener(preferenceChangeListener)
        super.onInactive()
    }
}

class SharedPreferenceIntLiveData(sharedPrefs: SharedPreferences, key: String, defValue: Int) :
        SharedPreferenceLiveData<Int>(sharedPrefs, key, defValue) {
    override fun getValueFromPreferences(key: String, defValue: Int): Int = sharedPrefs.getInt(key, defValue)
}

class SharedPreferenceStringLiveData(sharedPrefs: SharedPreferences, key: String, defValue: String) :
        SharedPreferenceLiveData<String>(sharedPrefs, key, defValue) {
    override fun getValueFromPreferences(key: String, defValue: String): String = sharedPrefs.getString(key, defValue)
}

class SharedPreferenceBooleanLiveData(sharedPrefs: SharedPreferences, key: String, defValue: Boolean) :
        SharedPreferenceLiveData<Boolean>(sharedPrefs, key, defValue) {
    override fun getValueFromPreferences(key: String, defValue: Boolean): Boolean = sharedPrefs.getBoolean(key, defValue)
}

class SharedPreferenceFloatLiveData(sharedPrefs: SharedPreferences, key: String, defValue: Float) :
        SharedPreferenceLiveData<Float>(sharedPrefs, key, defValue) {
    override fun getValueFromPreferences(key: String, defValue: Float): Float = sharedPrefs.getFloat(key, defValue)
}

class SharedPreferenceLongLiveData(sharedPrefs: SharedPreferences, key: String, defValue: Long) :
        SharedPreferenceLiveData<Long>(sharedPrefs, key, defValue) {
    override fun getValueFromPreferences(key: String, defValue: Long): Long = sharedPrefs.getLong(key, defValue)
}

class SharedPreferenceStringSetLiveData(sharedPrefs: SharedPreferences, key: String, defValue: Set<String>) :
        SharedPreferenceLiveData<Set<String>>(sharedPrefs, key, defValue) {
    override fun getValueFromPreferences(key: String, defValue: Set<String>): Set<String> = sharedPrefs.getStringSet(key, defValue)
}

fun SharedPreferences.intLiveData(key: String, defValue: Int): SharedPreferenceLiveData<Int> {
    return SharedPreferenceIntLiveData(this, key, defValue)
}

fun SharedPreferences.stringLiveData(key: String, defValue: String): SharedPreferenceLiveData<String> {
    return SharedPreferenceStringLiveData(this, key, defValue)
}

fun SharedPreferences.booleanLiveData(key: String, defValue: Boolean): SharedPreferenceLiveData<Boolean> {
    return SharedPreferenceBooleanLiveData(this, key, defValue)
}

fun SharedPreferences.floatLiveData(key: String, defValue: Float): SharedPreferenceLiveData<Float> {
    return SharedPreferenceFloatLiveData(this, key, defValue)
}

fun SharedPreferences.longLiveData(key: String, defValue: Long): SharedPreferenceLiveData<Long> {
    return SharedPreferenceLongLiveData(this, key, defValue)
}

fun SharedPreferences.stringSetLiveData(key: String, defValue: Set<String>): SharedPreferenceLiveData<Set<String>> {
    return SharedPreferenceStringSetLiveData(this, key, defValue)
}