Category: android

ConstraintLayout – Guidelines, Barriers, Chains and Groups

ConstraintLayout – Guidelines, Barriers, Chains and Groups

Since my initial blog post about ConstraintLayout, there have been a whole bunch of new features added (and lots of improvements) to ConstraintLayout. This blog post aims to cover some of the new features, namely Guidelines, Barriers, Chains and Groups.

Some of these features require using Android Studio 3.0 Beta 5 and the beta version of ConstraintLayout. In order to use the beta version of ConstraintLayout, make sure you have at least the following dependency in your app level build.gradle file:


Guidelines are small visual helpers to design layouts with. Views can be aligned to a guideline which can simplify layouts, especially if you have the same margin values duplicated on a lot of elements.

Guidelines can be specified in dp from start or end of the screen or they can be a percentage of the width of the screen. To cycle through the different guideline modes, you can click the round icon at the top of the guideline.

To create a guideline and use it, see below:

Guidelines in ConstraintLayout
Guidelines in ConstraintLayout

If you are curious as to how a guideline looks in XML, this is what it looks like:

Other views in the layout can then constrain themselves to the guideline.


Barriers are one of my favourite features in ConstraintLayout. A barrier is an invisible view that contains reference to the views that you wish to use to form a “barrier” against. If one of the views grows, the barrier will adjust its size to the largest height or width of the referenced items. Barriers can be vertical or horizontal and can be created to the top, bottom, left or right of the referenced views. Other views can then constrain themselves to the barrier.

Below is an example of creating a barrier from two views and constraining a view to it. As you can see, adjusting the size of the TextView, the barrier adjusts its size and the constrained view moves.

Barriers in ConstraintLayout
Barriers in ConstraintLayout

If you are curious as to how this is created, this is what it looks like in XML:

The property app:constraint_referenced_ids contains a list of view ids that will form the barrier.


Chains allow you to control the space between elements and how the elements use the space. To create a chain, select the elements that you want to form part of the chain, and then right click – “Chain” – “Create Horizontal/Vertical Chain”.

Chains in ConstraintLayout Android
ConstraintLayout Chains

You are then able to cycle through the different chain modes. There are four different modes: spread_inside, packed, spread and weighted.

Different Chain Modes in ConstraintLayout

The XML for creating a chain is different in that all the views have the constraints defined on them and the first item in the chain specifies the chainStyle.


With groups, you can logically group together certain views. Don’t confuse this with normal ViewGroups in Android though. A group in ConstraintLayout only contains references to the view ids and not nesting the views inside a group. With a group, you can set the visibility of all views in the group, by just setting the groups visibility without needing to set every view’s visibility. This is useful for things such as error screens or loading screens where a few elements need to change their visibility at once.

To add a group – see below:

Groups in ConstraintLayout

If you are wondering how this looks in XML, here it is:

The property app:constraint_referenced_ids contains a list of all the view ids that need to be a part of the group.

Practical Example

I wanted to try recreate the Google Play Movies detail screen only using ConstraintLayout to see how much I could build in the UI Editor. The results completely blew me away.

ConstraintLayout Android Example
ConstraintLayout Android Example

For the code relating to this layout, checkout this Github repository.

There are loads more features in ConstraintLayout, so subscribe to the blog to receive updates. Have anything to add? Let me know on Twitter.

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Highlights from Google Developer Days Europe 2017 – Kraków, Poland

Highlights from Google Developer Days Europe 2017 – Kraków, Poland

This past week I was in Kraków for the Google Developer Days Europe Conference and the Google Developer Experts Summit. There was a lot to learn about new technology and I enjoyed meeting and spending time with many developers from across the globe. I didn’t know much about Kraków before visiting but I’m really thankful to have spent the past week there, exploring the area, having great conversations and eating lots of pierogis!

Google Developer Experts Summit 2017

The Summit was held in the Polish Aviation Museum which was such a great venue for the conference. I loved the attention to detail at the conference. The conference started with an address by Jason Titus and had some really good content to follow. The summit is a yearly event that all Google Developer Experts are invited to attend. The summit covers a whole range of content about Android, Web, IoT etc.

Google developer Experts Summit
Google Developer Experts Summit – Highlights

Google Developer Days Europe – 2017

After the Google Developer Experts Summit, GDD Europe took place in the ICE Conference centre. The conference was a huge success, I was very lucky to be involved in the event by speaking about Android Things!

Speaking in the main auditorium in front of a few hundred people was my highlight of the conference (and also pretty scary!). Overall, I had a great time speaking and you can catch my presentation below.

Some of the other highlights for me of the event included all the cool IoT stuff you could play with at the Android Things booth, including the Android DrawBot. The DrawBot took a photo and then converted your face into a line drawing.

Android Things IoT at Google Developer Days Europe
Android Things IoT at Google Developer Days Europe

There was a lot to see and take in during this conference. I especially enjoyed Florina’s talk about Architecture components, Wojtek’s talk about Android Performance Tools. Another talk that was really interesting was ARCore SDK, which went into detail around Android’s new Augmented Reality SDK and how you can use it.

Free Android Things IoT kits were also handed out, the kit included the Pico i.MX7D device and a few peripherals.

Android Things Kit at Google Developer Days Europe
Android Things Kit from GDD Europe

As with most Google Conferences, there is so much to see and do, including great conversations with highly skilled developers. If you ever are presented with the opportunity of attending a Google conference, I highly encourage you to go.

Google Developer Days Europe Highlights

Kraków is a beautiful city and I thoroughly enjoyed my time there. Till next time! Thanks #GDDEurope 😃

Wawel Castle
Wawel Royal Castle in Kraków
Android Oreo – (8.0) – Features I’m excited about

Android Oreo – (8.0) – Features I’m excited about

Google has officially announced the next version of the Android operating system and it is called Android Oreo! If you are a mad Android fanatic like me, then you probably already know this by now. Historically, Google has named its versions of Android after different tasty sweets or desserts, each version is named alphabetically – it started with Cupcake, Donut, to the more recent ones such as Marshmallow and Nougat. One of the big reasons why I love Android is because of the delicious sweet treats that the releases are named after.

There was a buzz of excitement at Google I/O 2017 this year with people trying to guess the next version name. Suggestions of Oatmeal Cookie, Oreo, Orange soda and some even suggested Ouma Rusks (okay I admit – that one was all me). On Monday the 21st of August, the announcement was made that Android O would be called Android Oreo!

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Resources for Getting Started with Modern Android Development

Resources for Getting Started with Modern Android Development

 After putting together resources for the Mobile Developer Graduate Program that we run at DVT, I realised that the content I referenced could be a great guide for getting started with Modern Android development.

It is worth noting that we have a very hands-on approach to training the graduates at DVT. We run workshops as well as practical projects to ensure our graduates have a solid understanding of Android development.

With the vast amount of content available online, when I started Android development I didn’t really know where to look or what I should be aware of when developing an app. Having a concise list like the one in this blog post would have been invaluable for me when I started out. I hope you find value in it too.

Here is a list of links, code labs and reference material that would be useful for any developer that wants to get started in the world of Android development.

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Android Architecture Components – Looking at Lifecycles – Part 3

Android Architecture Components – Looking at Lifecycles – Part 3

In the previous posts (part 1 and part 2), we looked into the new Architecture Components that were announced at Google I/O 2017. The Android Architecture components are a welcome addition to the Android Platform. Previously, it was difficult to architect Android applications as there were no official guidelines. The new Architecture Components help solve some of the more difficult problems that you may have faced when building your Android applications in the past.

In this blog post, we will examine the new classes that were introduced to handle Lifecycle changes.

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