Android Studio MainActivity.kt can't reference ids in main

I am new to Android Studio. I wrote a simple code in the main_activity.xml file, with ids. But when I try to reference the ids from my MainActivity.kt file. It shows an error Unresolved reference: btnDatePicker i.e an unresolved error.

I don't know what wrong. Here's a screenshot of my MainActivity.kt file. As you can see, when I try to call the id btnDatePicker, it returns an error.

And Here's a screenshot of my activity_main.xml, as you'll see I have circled the particular id I'm trying to reference.

CodePudding user response：

Id cannot be referenced directly

Under normal conditions, you can bind the control using the following code:

val button = findViewById<Button>(R.id.btnDatePicker)

and if you want to use id directly, i think this article can help you View Binding

CodePudding user response：

Just try to rebuild project,Build -> Rebuild project We have 2 variant and I recommend it. I recommend you use View Binding. Because Koltin synthetic(just writing id element) is deprecated.

To enable view binding in a module, set the viewBinding build option to true in the module-level build.gradle file, as shown in the following example:

android {
...
buildFeatures {
    viewBinding = true
}

}

Usage

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

then use your xml elements

binding.btnDataPicker.setOnClickListener {
   ...
}