关于LifecycleEventObserver

Lifecycle可以添加观察者，从而让其它工作与周期变化保持一致

比如我们希望Dialog和Activity的生命周期一致，能够在Activity结束时自动关闭

可以通过如下代码来实现

与Lifecycle同步的Dialog

package com.android.code

import android.app.Dialog
import androidx.activity.ComponentActivity
import androidx.lifecycle.Lifecycle
import androidx.lifecycle.LifecycleEventObserver
import androidx.lifecycle.LifecycleOwner

class LifecycleDialog(
    private val activity: ComponentActivity
) : Dialog(activity), LifecycleEventObserver {

    init {
        activity.lifecycle.addObserver(this)
    }

    override fun onStateChanged(source: LifecycleOwner, event: Lifecycle.Event) {
        if (event == Lifecycle.Event.ON_DESTROY && isShowing) dismiss()
    }
}