本文主要是介绍Kotlin版 自定义的LiveDataBus，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
先上代码：
object LiveDataBusKT {// private val bus: MutableMap<String, BusMutableLiveData<Any>> by lazy { HashMap() }private val MAX_BUS_COUNT = 100 // 最大允许的 bus 对象数量private val bus: LruCache<String, BusMutableLiveData<Any>> = LruCache(MAX_BUS_COUNT)//暴露一个线程安全的，给外界注册，订阅者关系@Synchronizedfun <T>with(key:String,type:Class<T>,isStick: Boolean =true):BusMutableLiveData<T>{var liveData = bus.get(key)if (liveData == null) {liveData = BusMutableLiveData(isStick)bus.put(key, liveData)}
// if (!bus.containsKey(key)){
// bus[key] = BusMutableLiveData(isStick)
// }return bus[key] as BusMutableLiveData<T>}class BusMutableLiveData<T> private constructor() :MutableLiveData<T>(){var isStick =false //开启，关闭 粘性//次构造constructor(isStick: Boolean):this(){this.isStick =isStick}//hookoverride fun observe(owner: LifecycleOwner, observer: Observer<in T>) {super.observe(owner, observer)if (!isStick){hook(observer =observer)}else{}}private fun <T> hook(observer: Observer<in T>) {// 获取mLastVersionval liveDataClass = LiveData::class.java// getDeclaredField是可以获取一个类的所有字段.// getField只能获取类的public 字段.val mObserversField = liveDataClass.getDeclaredField("mObservers")mObserversField.isAccessible = true //private 修饰也可以访问val mObserversObject = mObserversField.get(this)// 获取 private SafeIterableMap<Observer<? super T>, ObserverWrapper> mObservers = new SafeIterableMap<>();val mObserversClass = mObserversObject.javaClass// 获取 mObservers 的 get方法 protected Entry<K, V> get(K k){}val get = mObserversClass.getDeclaredMethod("get", Any::class.java)get.isAccessible = true// 执行get方法val invoke = get.invoke(mObserversObject, observer)// 获取 entry 中 的 valuevar observerWrapper: Any? = nullif (invoke != null && invoke is Map.Entry<*, *>) {observerWrapper = invoke.value}if (observerWrapper == null) {throw NullPointerException("observerWrapper is null")}// 得到observerWrapper的类对象val superclass = observerWrapper.javaClass.superclassval mLastVersionField = superclass.getDeclaredField("mLastVersion")mLastVersionField.isAccessible = true// 得到mVersionval mVersionField = liveDataClass.getDeclaredField("mVersion")mVersionField.isAccessible = true// 版本对齐val versionValue = mVersionField.get(this)mLastVersionField.set(observerWrapper, versionValue)}}
}为了开启，关闭粘性事件，使用了 isStick 控制。
通过继承 MutableLiveData，在observe的时候hook 获取 mLastVersion 和mVersion，进行版本对齐
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