CODEWITHSUNDEEP
androidkotlin
hewa jalal
hewa jalal

Reputation: 963

i don't undertsand how these two line of kotlin code work

class MainActivity : AppCompatActivity() {
    private lateinit var binding: ActivityMainBinding
    private val myName:MyName = MyName("Kotlin noob")
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding = DataBindingUtil.setContentView(this, R.layout.activity_main)
        binding.myName = myName //line 1
        binding.doneButton.setOnClickListener {
            addName(it)
        }
    }


    fun addName(view: View) {

        myName?.nickName = nickName_edit.text.toString() //line 2
        binding.showNameTextView.text = "hello ${binding.enterNameEditText.text}"
        binding.showNameTextView.visibility = View.VISIBLE
        binding.enterNameEditText.visibility = View.GONE
        view.visibility = View.GONE
    }

//this is the class used for data 
data class MyName(var name:String="", var nickName:String="")
}

how the commented code work ? i mean in line 1 how are we assigning myName to myName they are the same thing, and how we can assign reference variables to each ? and in line 2 what is that ? after myName

Upvotes: 0

Views: 144

Answers (1)

Prethia
Prethia

Reputation: 1203

Bindings are generated in runtime from your xml file, in this case 

R.layout.activity_main

First things first, if your layout had different name then the name of generated binding would also be different. 

R.layout.activity_test // ActivityTestBinding

Now in your layout you have a view with identifier myName. Thats why your generated class ActivityMainBinding can find myName. So binding.myName refers to an element in your xml while myName refers to the object you created. This is more related to using databinding, you should do the identical thing when writing with Java as well.

? is just an operator you can use with nullable objects. In java, you can write this 

if(myName != null){ 
    myName.nickName = nickName_edit.text.toString() 
}

Upvotes: 1

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