I am working with the codelab:
class MainActivity : AppCompatActivity() {
private val myName: MyName = MyName("Aleks Haecky")
...
the MyName class:
data class MyName(var name: String = "", var nickname: String = "")
databinding variable in the layout:
<data>
<variable
name="myName"
type="com.example.aboutme.MyName" />
</data>
the code in main activity where an an event handler is set
...
binding.doneButton.setOnClickListener {
addNickname(it)
}
}
private fun addNickname(view: View) {
binding.apply {
myName.nickname = nicknameEdit.text.toString()
...
why does the variable myName generate the following error?
Only safe (?.) or non-null asserted (!!.) calls are allowed on a nullable receiver of type MyName?
myName is not declared nullable. So why myName?.nickname is needed?
it's because the variable myName in
binding.apply {
myName?.nickname = nicknameEdit.text.toString()
invalidateAll()
...
}
is not refers to this
private val myName: MyName = MyName("Aleks Haecky")
but it refers to the myName in this xml
<data>
<variable
name="myName"
type="com.example.aboutme.MyName" />
</data>
And all variables that you define on layout xml file are nullable. That's why you need a safe call (?.) every time you want to access it.