Kotlin observable properties

Properties.kt

/**
** 为KProperty0添加一个扩展函数addObserver()，用来监听当值发生变化的时候刷新observer代码块
**/

fun <T> KProperty0<T>.addObserver(observer: (T) -> Unit) {
    (getDelegate(this) as ObservableProperty<T>?)?.addObserver(observer)
}

private fun <T> getDelegate(kProperty: KProperty0<T>) : Any? {
    val owner = (kProperty as PropertyReference).owner
    val containerClass: Class<*>
    try {
        containerClass = (owner!!::class.members as ArrayList).firstOrNull { it.name == "jClass" }?.call(owner) as Class<*>
    } catch (e: Exception) {
        throw IllegalArgumentException("No such property 'jClass'")
    }
    containerClass.declaredFields.firstOrNull { it.name == kProperty.name + "\$delegate" }?.let { field ->
        field.isAccessible = true
//        try {
//            val modifyFiled = field.javaClass.getDeclaredField("modifiers")
//            modifyFiled.isAccessible = true
//            modifyFiled.setInt(field, modifyFiled.getInt(field) and Modifier.FINAL.inv())
//        } catch (e: NoSuchFieldException) {
//            e.printStackTrace()
//        }
         return field.get(kProperty.boundReceiver)
    }
    return null
}

open class ObservableProperty<T>(v: T) : ReadWriteProperty<Any?, T> {
    val observers: MutableSet<(T) -> Unit> = LinkedHashSet()
    private var value: T = v

    override fun getValue(thisRef: Any?, property: KProperty<*>): T {
        return value
    }

    override fun setValue(thisRef: Any?, property: KProperty<*>, value: T) {
        this.value = value
        observers.forEach { it(value) }
    }

    fun addObserver(observer: (T) -> Unit) {
        observers.add(observer)
    }
}

原来的这段代码用的是

fun <T> KProperty0<T>.addObserver(observer: (T) -> Unit) {
    (apply { isAccessible = true }.getDelegate() as MutableProperty<T>).addObserver(observer)
}

发现不稳定，会存在报错的情况，所以用java反射的方式来获取delegate对象