AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    ...>
    ...
    <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
    ...
    <application
        ...>
        ...
        <receiver
            android:name=".receivers.BootCompletedReceiver"
            android:enabled="true"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.BOOT_COMPLETED" />
            </intent-filter>
        </receiver>
    </application>
</manifest>

BootCompletedReceiver.java

public class BootCompletedReceiver extends BroadcastReceiver {
	public BootCompletedReceiver() {
	}

	@Override
	public void onReceive(Context context, Intent intent) {
		// launching demo app
		context.startActivity(new Intent(context, MainActivity.class).setFlags(Intent.FLAG_ACTIVITY_NEW_TASK ));
	}
}

MainActivity.java

	private PowerManager.WakeLock mWakeLock;

    ....

	@Override
	protected void onCreate(Bundle savedInstanceState) {
	    super.onCreate(savedInstanceState)
	    // Some code ...
	    // Some more code ...
	    // More code ...
	    
        getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
	    getWindow().addFlags(WindowManager.LayoutParams.FLAG_DISMISS_KEYGUARD);
	    getWindow().addFlags(WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED);
	    getWindow().addFlags(WindowManager.LayoutParams.FLAG_TURN_SCREEN_ON);
	    
	    PowerManager pm = (PowerManager) getSystemService(POWER_SERVICE);
		mWakeLock = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, getClass().getName());
		mWakeLock.setReferenceCounted(false);
		mWakeLock.acquire();
	}
	
	...
	
	@Override
	protected void onDestroy() {
		mWakeLock.release();
		super.onDestroy();
	}