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116 changes: 49 additions & 67 deletions
116
JetpackMvvm/src/main/java/me/hgj/jetpackmvvm/callback/livedata/UnPeekLiveData.kt
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,83 +1,65 @@ | ||
| package me.hgj.jetpackmvvm.callback.livedata | ||
|
|
||
| import androidx.lifecycle.LifecycleOwner | ||
| import androidx.lifecycle.LiveData | ||
| import androidx.lifecycle.MutableLiveData | ||
| import androidx.lifecycle.Observer | ||
| import me.hgj.jetpackmvvm.ext.util.notNull | ||
| import java.util.* | ||
|
|
||
| /** | ||
| * 防止数据倒灌的LiveData | ||
| * @author : hgj | ||
| * @date : 2020/7/16 | ||
| * 作者 : hegaojian | ||
| * 时间 : 2019/12/17 | ||
| * 仅分发 owner observe 后 才新拿到的数据 | ||
| * 可避免共享作用域 VM 下 liveData 被 observe 时旧数据倒灌的情况 | ||
| */ | ||
|
|
||
| class UnPeekLiveData<T> : MutableLiveData<T>() { | ||
| private var isCleaning = false | ||
| private var hasHandled = true | ||
| private var isDelaying = false | ||
| private val mTimer = Timer() | ||
| private var mTask: TimerTask? = null | ||
| private var DELAY_TO_CLEAR_EVENT = 1000 | ||
|
|
||
| override fun observe(owner: LifecycleOwner, observer: Observer<in T>) { | ||
| super.observe(owner, Observer { | ||
| if (isCleaning) { | ||
| hasHandled = true | ||
| isDelaying = false | ||
| isCleaning = false | ||
| return@Observer | ||
| } | ||
| if (!hasHandled) { | ||
| hasHandled = true | ||
| isDelaying = true | ||
| observer.onChanged(it) | ||
| } else if (isDelaying) { | ||
| observer.onChanged(it) | ||
| } | ||
| }) | ||
| override fun observe( | ||
| owner: LifecycleOwner, | ||
| observer: Observer<in T> | ||
| ) { | ||
| super.observe(owner, observer) | ||
| hook(observer) | ||
| } | ||
|
|
||
| override fun observeForever(observer: Observer<in T>) { | ||
| super.observeForever(Observer { | ||
| if (isCleaning) { | ||
| hasHandled = true | ||
| isDelaying = false | ||
| isCleaning = false | ||
| return@Observer | ||
| private fun hook(observer: Observer<in T>) { | ||
| val liveDataClass = LiveData::class.java | ||
| try { | ||
| //获取field private SafeIterableMap<Observer<T>, ObserverWrapper> mObservers | ||
| val mObservers = liveDataClass.getDeclaredField("mObservers") | ||
| mObservers.isAccessible = true | ||
| //获取SafeIterableMap集合mObservers | ||
| val observers = mObservers[this] | ||
| val observersClass: Class<*> = observers.javaClass | ||
| //获取SafeIterableMap的get(Object obj)方法 | ||
| val methodGet = | ||
| observersClass.getDeclaredMethod("get", Any::class.java) | ||
| methodGet.isAccessible = true | ||
| //获取到observer在集合中对应的ObserverWrapper对象 | ||
| val objectWrapperEntry = methodGet.invoke(observers, observer) | ||
| var objectWrapper: Any? = null | ||
| if (objectWrapperEntry is Map.Entry<*, *>) { | ||
| objectWrapper = objectWrapperEntry.value | ||
| } | ||
| if (!hasHandled) { | ||
| hasHandled = true | ||
| isDelaying = true | ||
| observer.onChanged(it) | ||
| } else if (isDelaying) { | ||
| observer.onChanged(it) | ||
| } | ||
| }) | ||
| } | ||
|
|
||
| /** | ||
| * 重写的 setValue 方法 | ||
| * @param value | ||
| */ | ||
| override fun setValue(value: T?) { | ||
| hasHandled = false | ||
| isDelaying = false | ||
| super.setValue(value) | ||
| mTask.notNull({ | ||
| it.cancel() | ||
| mTimer.purge() | ||
| }) | ||
| mTask = object : TimerTask() { | ||
| override fun run() { | ||
| clear() | ||
| if (objectWrapper == null) { | ||
| throw NullPointerException("ObserverWrapper can not be null") | ||
| } | ||
| //获取ObserverWrapper的Class对象 LifecycleBoundObserver extends ObserverWrapper | ||
| val wrapperClass: Class<*>? = objectWrapper.javaClass.superclass | ||
| //获取ObserverWrapper的field mLastVersion | ||
| val mLastVersion = | ||
| wrapperClass!!.getDeclaredField("mLastVersion") | ||
| mLastVersion.isAccessible = true | ||
| //获取liveData的field mVersion | ||
| val mVersion = liveDataClass.getDeclaredField("mVersion") | ||
| mVersion.isAccessible = true | ||
| val mV = mVersion[this] | ||
| //把当前ListData的mVersion赋值给 ObserverWrapper的field mLastVersion | ||
| mLastVersion[objectWrapper] = mV | ||
| mObservers.isAccessible = false | ||
| methodGet.isAccessible = false | ||
| mLastVersion.isAccessible = false | ||
| mVersion.isAccessible = false | ||
| } catch (e: Exception) { | ||
| e.printStackTrace() | ||
| } | ||
| mTimer.schedule(mTask, DELAY_TO_CLEAR_EVENT.toLong()) | ||
| } | ||
|
|
||
| private fun clear() { | ||
| hasHandled = true | ||
| isDelaying = false | ||
| } | ||
| } |
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