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David Vávra
Google Developer Expert for Android, Fouder & CEO at Step Up Labs, GDG Prague organizer, Early Adopter
Google Developer Expert for Android, Fouder & CEO at Step Up Labs, GDG Prague organizer, Early Adopter


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I'm a main organizer of DevFest CZ 2017. We just released a bunch of info:
- creepy teaser
- early bird tickets (till Sep 30) at
- venue
- partners & team

All on our new website based on Project Hoverboard from great +GDG Lviv

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IoT Window Opener - Smarwi

Me & my girlfriend had a problem during these hot summer nights: if the windows are closed during the night, it gets really hot and it's hard to sleep. Also, the CO2 level increases and the air gets heavy. However, if the windows are opened during the night, the temperature is OK but the street gets busy around 6am which wakes us up.

First, I was thinking about buying some AC, but we live in a rented apartment and can't drill a hole through the wall. But I thought that all we need is to keep the window open during the night and closed from 6 AM - 9 AM. How about some IoT device to do that?

I was googling if something like that exists and I was surprised to find Czech company Vektiva which does exactly that! I sent them a message and they told me they haven't launched the product yet, but I could be part of the pilot for a discounted price of 2300 CZK. I went for it.

It works as expected, see the attached video to watch opening/closing of the window in action. You can configure when the window should open/close based on time. I asked if the device has some API and Ventiva send me the one they currently develop. I paired it with Google Home via IFTTT and now I can open the window by voice :)

The only downside is the UI for configuring the device. It's too complicated and not intuitive, which makes it look like it was created by developers without designers :) But I shared a specific feedback with Ventiva and they are working on making the UI better for the public launch. Otherwise, I would recommend this device for anyone who wants to open/close windows automatically. Get more details at

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A big milestone for our company. Featuring two-way synchronization between AppEngine (old Android app, iOS and web) and Firebase Realtime Database (new Android app). Heavy use of Cloud Functions for Firebase. Cross-platform tests of app logic using Cucumber. And Kotlin+RxJava of course :)
🎉 A brand new Settle Up Beta for Android is here! If you want to be among the first to test it, go to

It is an update to the existing app so you won't lose any data, but it might still need some polishing 😉 Please report any bugs or unexpected behaviour, thank you!

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CZ Kotlin Meetup #2: Převod Android projektu z Javy

Pomáhám v rozjezdu této komunity a live codingem ukáži, jak je jednoduché (a kde to zadrhává) převést Androidí Java projekt do Kotlinu. Budu to ukazovat na sample aplikaci pro Android Architecture Components (horká novinka z I/O). Akce se koná 24.7. v Avast kantýně, doražte!

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Podcast z lesa natočený na 100 let výročí +GDG Jihlava je venku. Dík moc za pozvání!
CZ Popcast 172 - Uživatelské komunity
Lojza Holub, coby podcastový panic, se v tomto díle rozpovídal o Google User Group Jihlava a nelehké cestě k jejímu vytvoření. Zároveň se natáčení zúčastnili Lojzovi hosté z celé ČR, kteří přispěchali s vlastními názory na budování uživatelských komunit. Te...

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Can your test Cloud Functions for +Firebase and deploy them from CI? Yes!

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CfP for DevFest in Prague is now open

- November 4-5, 2017
- 600 attendees
- all talks recorded
- it will be a developer festival, not yet another conference. Meaning gamification, role-playing, Google I/O-inspired afterparty and more
- English is an official language
- beautiful city Prague

Submit your talk or workshop!

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16 Android GDEs are pro-Kotlin, one against.

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Firebase Remote Config codelab open-sourced

I was leading +Firebase Remote Config Codelab today at Lauchpad Build Prague event. I didn't find an official codelab for this, so I created my own. I'm open-sourcing it, it might be useful for others.

This codelab which will show you how to integrate Firebase Remote Config into your app and use it for A/B testing. Then you will learn how to measure results of A/B testing in Firebase Analytics. It took attendees about 40 minutes to finish.

#lpprague #launchpad #firebase #codelab
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