ViewModel类实现LifecycleObserver是否可行？

Question

阅读ViewModel概述，我想知道一个ViewModel同时成为LifecycleObserver是否可以接受？我的意图是在用户不与UI交互时断开Firebase监听器，并在用户与UI交互时重新连接它。就我所做的和所知道的而言，它完美地运作。但是，我担心这样做可能有问题（例如内存泄漏）。如果是这样，请问有替代方法吗？

class UserProfileViewModel : ViewModel(), LifecycleObserver {
    companion object {
        private const val TAG = "ProfileViewModel"
    }

    private lateinit var mUserProfile: MutableLiveData<DocumentSnapshot>
    private var mRegistration: ListenerRegistration? = null

    override fun onCleared() {
        Log.d(TAG, "onCleared")
        disconnectListener()
    }

    fun getUserProfile(): LiveData<DocumentSnapshot> {
        if (!::mUserProfile.isInitialized) {
            mUserProfile = MutableLiveData()
        }
        return mUserProfile
    }

    @OnLifecycleEvent(Lifecycle.Event.ON_RESUME)
    fun connectListener() {
        Log.d(TAG, "connectListener")
        val user = FirebaseAuth.getInstance().currentUser
        if (user == null) {
            Log.w(TAG, "User not signed in.")
            return
        }
        val firestore = FirebaseFirestore.getInstance()
        val docRef = firestore.collection(UsersContract.COLLECTION_NAME).document(user.uid)
        mRegistration = docRef.addSnapshotListener { snapshot, exception ->
            if (exception != null) {
                Log.w(TAG, "Failed to fetch user data", exception)
                return@addSnapshotListener
            }
            if (snapshot != null && snapshot.exists()) {
                mUserProfile.value = snapshot
            }
        }
    }

    @OnLifecycleEvent(Lifecycle.Event.ON_PAUSE)
    fun disconnectListener() {
        Log.d(TAG, "disconnectListener")
        mRegistration?.remove()
        mRegistration = null
    }
}

- Wei

Answer 1

如果您不关心将侦听器范围限定为恢复/暂停，则可以使用自定义LiveData来实现此目的。 您可以拥有一个类似UserProfileLiveData的自定义LiveData，继承自LiveData。

参考扩展LiveData - https://developer.android.com/topic/libraries/architecture/livedata#extend_livedata

- Karthi Keyan

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自定义的 LiveData 是否会作为 ViewModel 的属性呢？ - wonsuc