간단한 안드로이드 네트워크 체크

매니페스트 설정

인터넷 관련 권한을 사용하겠다고 매니페스트에 설정해두어야 한다.
AndroidManifest.xml

	...
	<uses-permission android:name="android.permission.INTERNET" />
	<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
	...

소스코드

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/textviewConnected"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

MainActivity

package com.example.networkcheck

import android.net.ConnectivityManager
import android.net.LinkProperties
import android.net.Network
import android.net.NetworkCapabilities
import android.os.Bundle
import android.util.Log
import android.widget.TextView
import androidx.appcompat.app.AppCompatActivity

class MainActivity : AppCompatActivity() {

    private val TAG = "MainActivity"

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val textviewConnected = findViewById<TextView>(R.id.textviewConnected)
        
        val connectivityManager = getSystemService(ConnectivityManager::class.java)
        connectivityManager.registerDefaultNetworkCallback(object : ConnectivityManager.NetworkCallback() {
            override fun onAvailable(network : Network) {
                Log.e(TAG, "The default network is now: " + network)
                runOnUiThread {
                    textviewConnected.text = "connected"
                }
            }

            override fun onLost(network : Network) {
                Log.e(TAG, "The application no longer has a default network. The last default network was " + network)
                runOnUiThread {
                    textviewConnected.text = "disconnected"
                }
            }

            override fun onCapabilitiesChanged(network : Network, networkCapabilities : NetworkCapabilities) {
                Log.e(TAG, "The default network changed capabilities: " + networkCapabilities)
            }

            override fun onLinkPropertiesChanged(network : Network, linkProperties : LinkProperties) {
                Log.e(TAG, "The default network changed link properties: " + linkProperties)
            }
        })

    }

}

참고

https://developer.android.com/training/basics/network-ops/reading-network-state?hl=ko