Layout Tip: Spacer in LinearLayout

Sometimes you want a layout where you want a spacer view that fills that pushes views to the right of it as far as they can. A common need to do something like this is when you roll your own Action Bar.

The action bar layout with the spacer view highlighted.

XML Layout

Explanation

When working with LinearLayout there's an option to use weights of free space rather than a set amount of space. When the layout measures its children it first sets the fixed sized children. For this layout that's everyone except the spacer view. Then it does another pass to measure the children that will fill dimensions based on their android:layout_weight parameter. Since there's only 1 view with this parameter, it fills up the remaining space.

Source Code
actionbar.xml | Project Page

Tip: Naming Resource Files

Android has a lot of resource files. These normally are XML files that have the <resource> root tag. The standard convention is to split resources out by type. The problem with this is these files tend to get very large and become unweildly to edit. A better way to organize them is by adding a category to the file name as well.

For example: strings_preferences.xml would contain all the strings that pertain to preferences while strings_application.xml will pertain to application strings that you might not want to localize.

Layouts sometimes become difficult to determine where they lie in the hierarchy. A good convention is to name layouts that are bound to an activity with the prefix activity_[activity name]. So MainActivity > activity_main.xml. Do this with fragments too: BuddyListFragment > fragment_buddylist.xml.

Android Starter Kit Part 1

I have a year of Android development experience. Which in framework years means I’m old enough climb up on the kitchen counter, take mom’s keys out of the cookie jar and buy over-the-counter whiteout.

Android, like any platform, has a learning curve. There are so many things to learn it can be overwhelming. Android’s main classes are probably the hardest to understand. Once you get over this hump it’s smooth sailing and there’s a constant draft.

Through experience grinding, I’ve found some tips that make everything a lot easier. Some of these were surprising. And others are fun. Below I compiled an Android Starter Kit. I made it from items dropped by Exceptions.

0. Take a Coffee Break (If you need it)
Java is the language you’ll be using in Android. You have to know it. Get some beans before you proceed any further. C#ers take note, Java is similar to C#. In fact, I learned C# by writing Java code in Visual Studio and fixing the compile errors.

1. Learn the Basics of Your Environment
Go to developer.android.com download all the goodies. Install, configure, setup your virtual device etc.

Create and launch the virtual device (AVD). I recommend using the latest Android version with the Google API for now. It’s the fastest. The AVD takes a long time to boot. So if you have OCD then go outside for a walk.

Lastly, leave all the acronyms you learned in school on the floor for a while, well except OOP. You’re code is going to be garbage and it had better be garbage. Focus on learning not perfection. Who says patterns make perfect anyway?

2. Get a REAL Android phone
Notice I didn’t say “device.” Get a phone, with or without contract with “stock firmware.” It’s important that you get real hardware because certain things don’t work in the emulator. For professionals, get at least 2. Both phones should be as opposite as possible. There’s so many of them out there and you can probably find one before your AVD finishes booting up. Here’s to REAL multiasking! And remember the best apps can only be written using the best hardware.

3. Plug in and Charge Up!
One of the great things about Android it it has a very healthy development community. There’s a ton of resources out there to help. Use these to start you off.
- Google Account - You should have one if you have an Android phone. If not create one through Gmail you’ll need it to register with the Android Market. www.gmail.com
- Stack Overflow - You’ll have questions. They’ve already been answered here. If they haven’t ask it and it’ll be answered in day at the most. www.stackoverflow.com
- Blogs - Keep a list of blogs that post code. These will give you ideas and provide insight that you never thought about. http://android-developers.blogspot.com is the official Android Development blog.

4. Tune In
A picture is worth a thousand words and that’s a lot to take in on one bite. You could choke. Those crazy diagrams and schematics are explained by Android Engineers on YouTube. What’s great about this is that they go a bit further and explain things that you should be aware of. Like: Why does an Activity get killed when the screen rotates? Good luck reading about that. I saw someone explain it to me in motion and I leveled up.

YouTube Channels:
AndroidDevelopers - http://www.youtube.com/user/androiddevelopers
GoogleDevelopers - http://www.youtube.com/user/googledevelopers
Oh and watch all the Google IO videos about Mobile and Android - http://code.google.com/events/io

Watching the videos takes a long time. Watch them at a leisurely pace. I suggest watching the important ones that are most relevant to you at the time and make room for the others as you have time.


At this point there’s plenty to do. Remember, don’t focus on code. Try to understand the concepts and how things work with Androids. Even if you know Java. Also be on the look out for classes the rhyme with Intent and Activity.