What is better android.R or custom R?

Question

When I started developping android applications, I had a tendency to define custom R values wherever I need, in particular in layout files. For instance:

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Answer 1

android.R is meant for utilizing resources built in to the operating system.

There are many images/layouts/etc... that come with the operating system that you can just reference using android.R

if you are referencing your own resources that you have created, most always use R. and in most situations I recommend trying to stay away from the built in resources as they change version to version.

Answer 2

There is no big advantage or disadvantage of the framework id vs the custom id in layouts.

Advantages of using framework identifiers:

• Avoid the creation of more identifiers. Saves one field in the apk (and there is an apk size limit).
• Must be used in some situations, like ListActivity

Drawbacks of using framework identifiers:

• Don't provide a descriptive name

In both practices

• The code will work in the future
• Missing references are discovered at runtime, and hidden at compile time

I thought the the samples in the SDK would help me take a decision, and (guess what?) it doesn't. The Notepad and LunarLander applications use the android.R.id for the view identifiers, whereas the ApiDemos project uses custom identifiers.

Best practice for GestureBuilder which mixes both approaches? (@+id/addButton and @android:id/empty)

IHMO, worse practice for HelloActivity and JetBoy which define @+id/text @+id/Button01... This is not descriptive and could have been replaced by (@andoid:id/button1, or by @+id/startButton)

Answer 3

You need your own R.java class as it contains references to all of your resources (layouts, images, strings, etc.)

If you want to get a reference to a View with id of "myView", you would use R.id.myView. If you want to get a reference to built-in Android resources, you would use android.R.id.text

Take a look at the following page:

http://developer.android.com/guide/topics/resources/accessing-resources.html

Answer 4

Custom. The system-provided IDs come with a risk of referring, in code, to a resource that is not present in the project. Customs IDs exist iff there's a corresponding resource - a drawable, a view, a layout or what have you.