Update 1.2

README.md

@@ -39,4 +39,10 @@ You can also use the following to populate a container view with a preference fr
 
 ```java
 populateWithPreferences(int containerViewId, int preferencesResId)
+```
+
+Since version 1.2, you can also use property delegates (in Kotlin only):
+
+```kotlin
+val str by stringPref("pref_string", "default")
 ```

library/src/main/java/com/github/calintat/Delegates.kt

@@ -0,0 +1,108 @@
+package com.github.calintat
+
+import android.content.Context
+import kotlin.reflect.KProperty
+
+/**
+ * A preference getter such as [getBoolean] or [getString].
+ */
+private typealias Get<T> = Context.(String, T) -> T
+
+/**
+ * A preference putter such as [putBoolean] or [putString].
+ */
+private typealias Put<T> = Context.(String, T) -> Unit
+
+/**
+ * Returns a property delegate for a read/write property corresponding to a boolean preference.
+ * Note that this uses the default shared preferences of the receiver context.
+ * Changing the value of the property will be reflected in the shared preferences.
+ *
+ * @param key The name of the preference used as a backing field for the property.
+ * @param defValue The default value of the property if the preference does not exist.
+ *
+ * @throws ClassCastException if there is a preference with this name that is not a boolean.
+ */
+fun Context.booleanPref(key: String, defValue: Boolean = false): PreferenceProperty<Boolean> {
+
+    return PreferenceProperty(key, defValue, Context::getBoolean, Context::putBoolean)
+}
+
+/**
+ * Returns a property delegate for a read/write property corresponding to a float preference.
+ * Note that this uses the default shared preferences of the receiver context.
+ * Changing the value of the property will be reflected in the shared preferences.
+ *
+ * @param key The name of the preference used as a backing field for the property.
+ * @param defValue The default value of the property if the preference does not exist.
+ *
+ * @throws ClassCastException if there is a preference with this name that is not a float.
+ */
+fun Context.floatPref(key: String, defValue: Float = 0f): PreferenceProperty<Float> {
+
+    return PreferenceProperty(key, defValue, Context::getFloat, Context::putFloat)
+}
+
+/**
+ * Returns a property delegate for a read/write property corresponding to an int preference.
+ * Note that this uses the default shared preferences of the receiver context.
+ * Changing the value of the property will be reflected in the shared preferences.
+ *
+ * @param key The name of the preference used as a backing field for the property.
+ * @param defValue The default value of the property if the preference does not exist.
+ *
+ * @throws ClassCastException if there is a preference with this name that is not an int.
+ */
+fun Context.intPref(key: String, defValue: Int = 0): PreferenceProperty<Int> {
+
+    return PreferenceProperty(key, defValue, Context::getInt, Context::putInt)
+}
+
+/**
+ * Returns a property delegate for a read/write property corresponding to a long preference.
+ * Note that this uses the default shared preferences of the receiver context.
+ * Changing the value of the property will be reflected in the shared preferences.
+ *
+ * @param key The name of the preference used as a backing field for the property.
+ * @param defValue The default value of the property if the preference does not exist.
+ *
+ * @throws ClassCastException if there is a preference with this name that is not a long.
+ */
+fun Context.longPref(key: String, defValue: Long = 0): PreferenceProperty<Long> {
+
+    return PreferenceProperty(key, defValue, Context::getLong, Context::putLong)
+}
+
+/**
+ * Returns a property delegate for a read/write property corresponding to a string preference.
+ * Note that this uses the default shared preferences of the receiver context.
+ * Changing the value of the property will be reflected in the shared preferences.
+ *
+ * @param key The name of the preference used as a backing field for the property.
+ * @param defValue The default value of the property if the preference does not exist.
+ *
+ * @throws ClassCastException if there is a preference with this name that is not a string.
+ */
+fun Context.stringPref(key: String, defValue: String = ""): PreferenceProperty<String> {
+
+    return PreferenceProperty(key, defValue, Context::getString, Context::putString)
+}
+
+/**
+ * A property delegate of properties that use a preference as a sort of backing field.
+ *
+ * @param key The name of the preference used as a backing field for the property.
+ * @param defValue The default value of the property if the preference does not exist.
+ */
+class PreferenceProperty<T>(val key: String, val defValue: T, val get: Get<T>, val put: Put<T>) {
+
+    operator fun getValue(thisRef: Context, property: KProperty<*>): T {
+
+        return thisRef.get(key, defValue)
+    }
+
+    operator fun setValue(thisRef: Context, property: KProperty<*>, value: T) {
+
+        thisRef.put(key, value)
+    }
+}