How does the BINDING variable identifies the correct XML for my Android APP Screen using Java and Kotlin?

Question

My questions is relatively simple: How does the binding find the layout to my Main Actvity since I don't use the ID, I use the name "root". And how am I going to find different layouts to my other screens using the similar code?

MAIN ACTIVITY

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        var binding: ActivityMainBinding = ActivityMainBinding.inflate(layoutInflater) // variable binding to access layout views
        setContentView(binding.root) // here define o XML
    }
}

I'm new to view binding. I haven't found a good resource to study it yet.

Answer 1

The ActivityMainBinding is not named ActivityMainBinding because you use it in the MainActivity. It's generated based on a layout file that is named activity_main so technically you are using specific ID but not via layout resource.

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    var binding: ActivityMainBinding = ActivityMainBinding.inflate(layoutInflater)
    setContentView(binding.root)
}

is exactly the same as:

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)
}

without the utility of data binding ofc.

Once you have a layout that uses data binding structure, the binding is automatically generated. e.g. for layout activity_second there will be ActivitySecondBinding.