Android, how to determine if a reboot occurred?

Question

How would I programmatically determine when an android device has rebooted (whether on its own, or user initiated) ?

Answer 1

If you happen to want to know if the device has been rebooted in-app, then you can use this code.

fun hasDeviceBeenRebooted(app: Application): Boolean {
    val REBOOT_PREFS = "reboot prefs"
    val REBOOT_KEY = "reboot key"
    val sharedPrefs = app.getSharedPreferences(REBOOT_PREFS, 

    val expectedTimeSinceReboot = sharedPrefs.getLong(REBOOT_KEY, 0)
    val actualTimeSinceReboot = System.currentTimeMillis() - SystemClock.elapsedRealtime() // Timestamp of rebooted time

    sharedPrefs.edit().putLong(REBOOT_KEY, actualTimeSinceReboot).apply()

    return actualTimeSinceReboot !in expectedTimeSinceReboot.minus(2000)..expectedTimeSinceReboot.plus(2000) // 2 Second error range.
}

Answer 2

Use a BroadcastReceiver and listen to the broadcast Intent ACTION_BOOT_COMPLETED.

Answer 3

This snippet starts an Application automatically after the android-os booted up.

in AndroidManifest.xml (application-part):

// You must hold the RECEIVE_BOOT_COMPLETED permission in order to receive this broadcast. 
<receiver android:enabled="true" android:name=".BootUpReceiver"
        android:permission="android.permission.RECEIVE_BOOT_COMPLETED">

        <intent-filter>
                <action android:name="android.intent.action.BOOT_COMPLETED" />
                <category android:name="android.intent.category.DEFAULT" />
        </intent-filter>
</receiver>
[..]
<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
[..]

In Java Class

 public class BootUpReceiver extends BroadcastReceiver{

            @Override
            public void onReceive(Context context, Intent intent) {
                    Intent i = new Intent(context, MyActivity.class);  
                    i.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                    context.startActivity(i);  
            }

}

Answer 4

Set up a BroadcastReceiver and register it in your manifest to respond to the android.intent.action.BOOT_COMPLETED system even. When the phone starts up the code in your broadcastreceiver's onReceive method will run. Make sure it either spawns a separate thread or takes less than 10 seconds, the OS will destroy your broadcastreceiver thread after 10 seconds.