How to take screenshot of Composable functions in Jetpack Compose

Assuming a drawing app that allows users to export a canvas, or a simple image editing app that users can share the edited photo, there might be limited ways to convert a composable to a bitmap.

In this post, I will share my experience of using standard methods to convert a composable into a bitmap and store it as a PNG in internal storage.

According to official docs you can access the view version of your composable function using LocalView.current, and export that view to a bitmap file like this (the following code goes inside the composable function):

    val view = LocalView.current
    val context = LocalContext.current

    val handler = Handler(Looper.getMainLooper())
    handler.postDelayed(Runnable {
        val bmp = Bitmap.createBitmap(view.width, view.height,
            Bitmap.Config.ARGB_8888).applyCanvas {
        bmp.let {
            File(context.filesDir, "screenshot.png")
                .writeBitmap(bmp, Bitmap.CompressFormat.PNG, 85)
    }, 1000)

The writeBitmap method is a simple extension function for File class. Example:

private fun File.writeBitmap(bitmap: Bitmap, format: Bitmap.CompressFormat, quality: Int) {
    outputStream().use { out ->
        bitmap.compress(format, quality, out)

If you liked this approach, vote for the stackoverflow post. Looking forward to read your feedback soon! 🙂

Arduino USB Terminal

During the isolation period caused by Corona, I was playing around with Arduino as a quite small hobby in my free time to create a simple robot that is being controlled by Android. 🙂

The robot uses an Arduino and a Motor Shield to control the motors, but since I am an Android developer, I wanted to somehow make use of Android to control it. 📱🤖

The concept is simple: There is an Android phone on the robot which is connected to the Arduino via a Bluetooth cable and sends commands to Arduino to control the motors.

Because of that, I had to test the USB connection between the Android phone and the Arduino, so I created a simple terminal to achieve this. But the terminal can be used for many more purposes than testing this robot, so I decided to publish it as an open-source project on GitHub and also a free app on Google Play Store:

Get it on Google Play

The robot itself, is still under construction 🚧 🔨 and I will probably send a photo of it when it is done, but until then, please feel free to use the new Terminal and I am looking forward to receiving your feedback. 😉

Unit testing Android LiveData using Espresso with Kotlin? Not a mess anymore!

After searching a lot about how to test the live data returned by Room DAOs for unit testing, I found it would be a good idea to share it with other people. The language is Kotlin and I am using Robolectric to mock the context; But here, I just focus on the problem itself and I’m not gonna explain how to write the tests. You can of course check the links provided in the text.


I also have to mention that there are also other workarounds to achieve this, like using Mockito, but honestly in my opinion, this was the most clean approach. But if you prefer those ones, good luck with that. 😊


What did I want to do? Check if the LiveData objects returned by a DAO method are correct; And to have 100% test coverage on those files. 😉

What I did? Created a Kotlin extension function for LiveData object in my test class to block the main thread and wait for the observer to call onChange method and return the value. How? Using CountdownLatch. Read the answer to this Stack Overflow post.

private fun <T> LiveData<T>.blockingObserve(): T? {

    var value: T? = null
    val latch = CountDownLatch(1)
    val observer = Observer<T> {

        t ->
        value = t


    latch.await(2, TimeUnit.SECONDS)
    return value

The Problem: Although CountDownLatch is used to block the thread and wait for the value, but it would not block the thread and the value was always null. This is probably because of LiveData’s main feature which is usually being used in the main thread and obviously, it is not supposed to block the main thread, never!

Solution: Well, that’s pretty easy! You just need to add this rule to your test class:

val rule = InstantTaskExecutorRule()

It will allow the liveData observer to block the main thread and Viola!

Just don’t forget to add the core-testing dependency which is part of the Architecture library to your project and also match its version to the version of your current Architecture library that you’re using and everything will work like a charm:

testImplementation "android.arch.core:core-testing:1.1.1"

The answer to this post on StackOverflow also explains it.

Now the tests should work fine and as a reminder, I am running the tests as Local Unit Tests using Robolectric and not as Android Instrumented tests.

Good Luck Unit Testing 😊

Kotlin, the second official programming language for Android

Kotlin was being used in Android by Android Developers unofficially using libraries like ANKO. Yesterday, Kotlin was introduced as a second officially supported Android programming language in Google I/O.

Here are some links and resources to presentations and tools which I found useful for getting started with Kotlin for Android.

Here is an introduction presented by Wojtek Kaliciński which gives you a better perspective about how to use Kotlin in Android Studio 3.0:
Android Tool Time: Getting Started with Kotlin

I also found this presentation from Hadi Hariri in CERN a good resource to get up and running with Kotlin in about 45 minutes, I really encourage you to watch it.
Kotlin – Ready for production by Hadi Hariri

And finally download the new version of Android Studio 3.0 Canary from the official preview website.
Android Studio Preview Download

I hope these resources help jumpstart your next Android project using Kotlin and improve your productivity in Android Development.

Kotlin, die zweite offizielle Programmiersprache für Android

Kotlin wurde in Android von Android Developers inoffiziell mit Bibliotheken wie ANKO verwendet. Gestern wurde Kotlin als zweite offiziell unterstützte Android-Programmiersprache in Google I / O eingeführt.

Hier sind einige Links und Ressourcen zu Präsentationen und Tools, die ich für den Einstieg in Kotlin für Android nützlich fand.

Hier ist eine Einführung von Wojtek Kaliciński, die Ihnen eine bessere Perspektive über die Verwendung von Kotlin in Android Studio 3.0 bietet:
Android Tool Time: Getting Started with Kotlin

Ich habe auch diese Präsentation von Hadi Hariri im CERN eine gute Quelle gefunden, um mit Kotlin in ca. 45 Minuten aufzustehen, ich ermutige Sie wirklich, es zu sehen.
Kotlin – Ready for production by Hadi Hariri

Und schließlich laden Sie die neue Version von Android Studio 3.0 Canary aus der offiziellen Vorschau-Website herunter.
Android Studio Preview Download

Ich hoffe, diese Ressourcen helfen Jumpstart Ihre nächste Android-Projekt mit Kotlin und verbessern Sie Ihre Produktivität in Android Development.

اجرا نشدن adb بعد از اضافه شدن Android ADB به Environmet Variable های لینوکس

اخیرا یکی از دوست هام با سیستم عامل Ubuntu مشکلی پیدا کرده بود به این صورت که بعد از اضافه کردن ADB به مسیر سیستم, باز هم نمیتونست دستور
adb رو از هرجایی توی Terminal اجرا کنه.Screenshot from 2014-05-09 11:21:53

اول برای اطمینان از اینکه مسیر adb به environment variable ها اضافه شده باشه دستور زیر رو توی Terminal اجرا کردم

sudo gedit ~/.bashrc

 Screenshot from 2014-05-09 10:30:12

همونطور که توی تصویر زیر مشاهده میکنید مسیر های adb به درستی اضاف شدن و اصولا دستور adb باید توی ترمینال اجرا شه:


اما سیستم عامل پیغامی مبتنی بر اینکه این فایل وجود نداره رو نمایش میداد.

مشکل از اینجا بود که Android ADB یک فایل اجرایی 32bit بود و سیستم عامل دوست من 64bit.

با توجه به آموزسی که توی سایت گوگل در زمینه آماده سازی محیط برنامه نویسی اندروید داده شده بود باید پکیج ia32libs روی سیستم عامل های 64bit نصب شه تا بتونیم بعضی از فایل های اجرایی 32bit رو روی 64bit اجرا کنیم, برای اینکار میتونیم از دستور زیر استفاده کنیم:

sudo apt-get install ia32-libs

Screenshot from 2014-05-09 10:32:13

بعد از تمام شدن مراحل نصب سیستم رو restart میکنیم, و adb به خوبی اجرا میشه.

حالا سیستم عامل آمادست برای برنامه نویسی اندروید و استفاده از Android SDK.

برنامه ای ساده برای تست چگونگی استفاده از پایگاه داده در اندروید

امروز یک برنامه ی ساده برای تست کردن دیتابیس روی پلتفرم اندروید نوشتم که این برنامه به این صورت
کار میکنه که شما یک نام و نام خانوادگی رو توی فیلد های بالایی برنامه مینویسید و روی دکمه ی ذخیره در دیتابیس کلیک میکنید, برنامه پارامتر هایی که شما وارد کردید رو داخل دیتا بیس ذخیره میکنه و یه پیغام مبتنی بر اینکه  دیتا ذخیره شده به شما میده, حالا شما میتونید به این ترتیب هر تعداد اسمی که خواستید وارد کنید.


بعد از اینکار شما میتونید اطلاعاتی که داخل دیتا بیس ذخریه شده رو با نام جستجو کنید, برای اینکار شما یکی از اسم هایی که از قبل داخل دیتا بیس ذخیره کردید رو وارد میکنید و دکمه رو فشار میدید, حالا میبینید که متن زیر دکمه به نام خانوادگی مربوط به اسمی که شما وارد کردید تغییر میکنه.


برای دریافت سورس و پکیج برنامه روی دکمه ی دانلود کلیک کنید.