Role of R Files in Android Development
While creating a simple UI for my Android app, I discovered R files. All the books I’ve read so far (or tried to read) or the tutorials I’ve found online have told me to “ignore” them and get forward with my coding journey! Today, I want to express my gratitude towards all the R files that are camouflaged behind complex codes. You are seen. You are heard. Anyway with that stupid introduction out of the way, let us learn a bit more about R files and their important role.
In Android app development, “R” files refer to Resource files, which are automatically generated Java files that act as a reference to the various resources used in an Android project. These resources include layouts, strings, drawables, dimensions, colors, styles, and other similar elements. The R file plays a crucial role in accessing these resources programmatically in your code (written in Java or Kotlin).
But how are these files generated? How does Android Studio know which resource these files point towards? Is there an alternative way? (Yes, but is it any better?)
The resources in XML files (such as layouts, strings, drawables, etc.) are all assigned a unique resource ID. When you build your Android project (using Gradle, of course) these resources and their associated resource IDs are compiled. Based on the resources defined in XML files, the Android Gradle Plugin generates a corresponding R.java file for each resource type. These R.java files contain constant integer values representing the resource IDs and are placed in the “gen” (generated) directory of your project. Now, you (a developer) can use these resource IDs to access the resources in your Kotlin/Java code.
Simple, isn’t it? But if you really “hate” R files and want to use an alternative (but not so good) method then you would be a tad bit disappointed.
See, the entire reason the R files exist is because they make your work easier, more efficient and more convenient. One approach could be using the resources directly by using methods. For example, the ‘getResources()’ method provided by the Context class. This method allows you to access resources dynamically at runtime without relying on the R file for resource IDs. However, this approach is more prone to errors. It lacks type safety and may result in runtime errors if resource names are misspelled or modified. Another approach (that does not make sense to me) is manually defining constants in your code to represent resource IDs. Even if you get the resource ID right, it is important to note that these IDs change (due to updates or refactoring). So you would have to manually change each hardcoded constant in your project. I won’t even explain how crazy this method is, especially if you have multiple layouts (in large projects).
Android uses a combination of resource compilation and mapping to associate the resources declared in your project’s XML files with the corresponding integer IDs in the R.java files. While there are alternative ways to access resources in Android development (not really), R files remain the standard and recommended approach due to their efficiency, type-safety, and ease of use. It’s generally best to stick with R files unless you have a specific reason to use an alternative method.
