Broadcast receivers in Android

activity_main2.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <Button
        android:id="@+id/button_explicit_broadcast"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Explicit broadcast" />

    <Button
        android:id="@+id/button_implicit_broadcast"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="implicit broadcast" />


</LinearLayout>

AndroidManifetst.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    package="ru.maksim.sample">

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

    <application
        android:name=".MyApp"
        android:allowBackup="true"
        android:dataExtractionRules="@xml/data_extraction_rules"
        android:fullBackupContent="@xml/backup_rules"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.SampleApplication"
        tools:targetApi="31">

        <receiver
            android:name=".MyBootCompletedReceiver"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.BOOT_COMPLETED" />
            </intent-filter>
        </receiver>

        <receiver
            android:name=".MyReceiver"
            android:exported="false">
            <intent-filter>
                <action android:name="ru.maksim.sample.MY_ACTION" />
            </intent-filter>
        </receiver>

        <activity
            android:name=".ClientAppActivity"
            android:exported="true"
            android:theme="@style/Theme.SampleApplication.NoActionBar">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

ClientAppActivity.kt

class ClientAppActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main2)

        findViewById<Button>(R.id.button_explicit_broadcast).setOnClickListener {
            sendBroadcast(Intent(applicationContext, MyReceiver::class.java))
            // log printed:
            // MyReceiver#onReceive: Intent { flg=0x10 cmp=ru.maksim.sample/.MyReceiver }
        }

        findViewById<Button>(R.id.button_implicit_broadcast).setOnClickListener {
            sendBroadcast(Intent("ru.maksim.sample.MY_ACTION"))
            // nothing happens
        }
    }

}

MyBootCompletedReceiver.kt

class MyBootCompletedReceiver : BroadcastReceiver() {

    override fun onReceive(context: Context, intent: Intent) {
        // This method is called when the BroadcastReceiver is receiving an Intent broadcast.
        Log.d("SampleApp", "MyBootCompletedReceiver#onReceive: $intent")
        // Log printed after device reboot via adb reboot:
        // MyBootCompletedReceiver#onReceive: Intent { act=android.intent.action.BOOT_COMPLETED flg=0x89000010
    }
}

MyReceiver.kt

class MyReceiver : BroadcastReceiver() {

    override fun onReceive(context: Context, intent: Intent) {
        // This method is called when the BroadcastReceiver is receiving an Intent broadcast.
        Log.d("SampleApp", "MyReceiver#onReceive: $intent")
    }
}