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Grokking Android

Getting Down to the Nitty Gritty of Android Development

Posts tagged “Android”:

Creating Kotlin DSLs


Kotlin has many nice things going for it – be it null safety, data classes, extension functions, immutable collections or many other things. For me one additional thing is very interesting: The ability to create domain specific languages (DSLs) easily. Easily, because creating a DSL with Kotlin means that you simply choose to combine several […]  Continue Reading  “Creating Kotlin DSLs”

Android Things: Remote Controlled Car – What’s Coming Up


Being an Android Developer, Google’s announcement of Android Things immediately piqued my interest. As all the others I started out with buying one of the developer kits and then making some lights blink. Nice. But, well, if I have to be honest with myself, that was fun but actually of only limited use 🙂  Then […]  Continue Reading  “Android Things: Remote Controlled Car – What’s Coming Up”

Android’s ConstraintLayout: Align One View’s Edge to Another View’s Center


As you can see from the following excerpt of ConstraintLayout's supported attributes, there is no layout_constraintStart_toCenterX attribute. Thus you cannot directly align the left edge of one view to the center of another view. But ConstraintLayout is flexible enough to get your view aligned to the center of another view without such an attribute. Even […]  Continue Reading  “Android’s ConstraintLayout: Align One View’s Edge to Another View’s Center”

Some Thoughts on Android’s new ConstraintLayout and Android Studio’s new Design Editor


At this year’s IO Google introduced a new layout – the ConstraintLayout – and also presented it’s totally revamped layout editor. I am not going into how to use the layout. Google itself has done a good job in explaining it with its code lab “Using ConstraintLayout to design your views”. In this post I […]  Continue Reading  “Some Thoughts on Android’s new ConstraintLayout and Android Studio’s new Design Editor”

RxJava’s Side Effect Methods


RxJava’s Observable class has plenty of methods that can be used to transform the stream of emitted items to the kind of data that you need. Those methods are at the very core of RxJava and form a big part of it’s attraction. But there are other methods, that do not change the stream of […]  Continue Reading  “RxJava’s Side Effect Methods”

Why use Observable.create() and not just inherit from Observable?


When starting to use RxJava you have to create Observables. They are at the very core of RxJava. But how to do so? A look at the Observable class might make you dizzy. Looking at the source even more so. Not only does this beast consist of nearly 10.000 lines (though, 7600 lines of that […]  Continue Reading  “Why use Observable.create() and not just inherit from Observable?”

Selecting Items of a RecyclerView using StateListDrawables


Last week, after I published my introduction to RecyclerView Paul Betts asked on Twitter whether ItemDecorators are useful for displaying the selection state of items. Well, I think using them for selection is not the right way to go. Instead, I think that you should stick with StateListDrawables and the activated state. The use case […]  Continue Reading  “Selecting Items of a RecyclerView using StateListDrawables”

A First Glance at Android’s RecyclerView


At this year’s Google I/O, Google released a preview to the upcoming Android version. The so called L Developer Preview. This is a very big improvement over previous releases and I really love that Google is doing this. I think we all benefit by this decision. As developers and as consumers alike! Part of this […]  Continue Reading  “A First Glance at Android’s RecyclerView”

An XMPP Server for Google Cloud Messaging


In this post I am going to write about the server-side of upstream messages with Google Cloud Messaging. This is the second part of my three-part series on this topic. If you haven’t read the first part about the flow of events and the Android implementation of upstream messaging, please read that one first. The […]  Continue Reading  “An XMPP Server for Google Cloud Messaging”

Upstream Messages With Google Cloud Messaging


Google announced a new messaging model with Google Cloud Messaging on last years Google IO. This model allows for upstream messaging and for user specific notifications. This post is the first in a three-part series in which I am going to look into both these changes and to show you how to use them. I […]  Continue Reading  “Upstream Messages With Google Cloud Messaging”