【Android】【メモ】ActivityやFragmentのライフサイクルをオブザーバーで受け取る

概要

androidx.lifecycle:2.2.0 からライフサイクルのイベントをオブザーバー経由で受け取れるようになったため実装のメモ

環境

targetSdkVersion: 29
kotlin: 1.3.72
androidx.appcompat:appcompat: 1.1.0

実装

LifecycleEventObserver

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.util.Log
import androidx.lifecycle.Lifecycle
import androidx.lifecycle.LifecycleEventObserver

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        lifecycle.addObserver(LifecycleEventObserver { source, event ->
            when (event) {
                Lifecycle.Event.ON_CREATE -> {
                    Log.d("MainActivity", "on_create")
                }
                Lifecycle.Event.ON_START -> {
                    Log.d("MainActivity", "on_start")
                }
                Lifecycle.Event.ON_RESUME -> {
                    Log.d("MainActivity", "on_resume")
                }
                Lifecycle.Event.ON_PAUSE -> {
                    Log.d("MainActivity", "on_pause")
                }
                Lifecycle.Event.ON_STOP -> {
                    Log.d("MainActivity", "on_stop")
                }
                Lifecycle.Event.ON_DESTROY -> {
                    Log.d("MainActivity", "on_destroy")
                }
                else -> Log.d("MainActivity", "other")
            }
        })
    }
}

LifecycleOvserver を使った書き方

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.util.Log
import androidx.lifecycle.*

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        lifecycle.addObserver(object: LifecycleObserver {
            @OnLifecycleEvent(Lifecycle.Event.ON_CREATE)
            fun onCreate() {
                Log.d("MainActivity", "onCreate")
            }

            @OnLifecycleEvent(Lifecycle.Event.ON_RESUME)
            fun onResume() {
                Log.d("MainActivity", "onResume")
            }

            @OnLifecycleEvent(Lifecycle.Event.ON_START)
            fun onStart() {
                Log.d("MainActivity", "onStart")
            }

            @OnLifecycleEvent(Lifecycle.Event.ON_STOP)
            fun onStop() {
                Log.d("MainActivity", "onStop")
            }

            @OnLifecycleEvent(Lifecycle.Event.ON_PAUSE)
            fun onPause() {
                Log.d("MainActivity", "onPause")
            }

            @OnLifecycleEvent(Lifecycle.Event.ON_DESTROY)
            fun onDestroy() {
                Log.d("MainActivity", "onDestroy")
            }

            @OnLifecycleEvent(Lifecycle.Event.ON_ANY)
            fun onAny(source: LifecycleOwner, event: Lifecycle.Event) {
                Log.d("MainActivity", "onAny: $event")
            }
        })
    }
}