Kotlin error: Expected 2 parameters of types android.widget.CompoundButton!, kotlin.Boolean

Question

I have a Kotlin error saying

Expected 2 parameters of types android.widget.CompoundButton!, kotlin.Boolean

The red squiggly line is at the first { in the code below:

    alarmSwitch.setOnCheckedChangeListener(CompoundButton.OnCheckedChangeListener()
    { 
        fun onCheckedChanged(buttonView: CompoundButton, isChecked: Boolean)
        {

I tried:

buttonView: !CompoundButton, (says "Expecting comma or )" )
buttonView: CompoundButton!, (says "Unexpected Token")
buttonView!: CompoundButton, (says "Expecting comma or )" )
!buttonView: CompoundButton, (says "Expecting comma or )" )
buttonView: CompoundButton?, (says "Expected 2 parameters of types android.widget.CompoundButton!, kotlin.Boolean" )

The official Kotlin docs say:

Notation for Platform Types

As mentioned above, platform types cannot be mentioned explicitly in the program, so there’s no syntax for them in the language. Nevertheless, the compiler and IDE need to display them sometimes (in error messages, parameter info etc), so we have a mnemonic notation for them:

T! means “T or T?”,

(Mutable)Collection! means “Java collection of T may be mutable or not, may be nullable or not”,

Array<(out) T>! means “Java array of T (or a subtype of T), nullable or not”

I don't fully understand what the docs are saying. How would I fix this error?

mnishiguchi · Accepted Answer · 2017-06-26 14:16:28Z

3

We can also simplify the code using a lambda expression

alarmSwitch.setOnCheckedChangeListener { buttonView, isChecked -> /* whatever...*/ }

https://antonioleiva.com/functional-programming-android-kotlin-lambdas/

answered Jun 26, 2017 at 14:16

mnishiguchi

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Comments

pt2121 · Accepted Answer · 2015-12-08 01:47:40Z

1

I think you need the object keyword (object:) which is needed for creating an object of an anonymous class.

See Object declaration

Try this:

alarmSwitch.setOnCheckedChangeListener(object:OnCheckedChangeListener() {
  fun onCheckedChanged(buttonView:CompoundButton, isChecked:Boolean) {
    // whatever...
  }
})

Hope this helps

edited Dec 8, 2015 at 1:47

answered Dec 8, 2015 at 1:41

pt2121

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Comments

Dave · Accepted Answer · 2022-03-17 09:07:49Z

0

checkboxQuickApproval.setOnCheckedChangeListener(object : CompoundButton.OnCheckedChangeListener {
   override fun onCheckedChanged(buttonView: CompoundButton?, isChecked: Boolean) {
        if (isChecked) {
            viewModel.onChangeCheckboxValue(isChecked) 
        }
    }
})

edited Mar 17, 2022 at 9:07

Dave

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answered Mar 17, 2022 at 8:33

Sajal Gupta

12 bronze badges

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