How to call function from object?

Question

I can't call function of my class from object inside this class. How should i do this ?

 class LoginActivity: AppCompatActivity(){
    override fun onCreate(savedInstanceState: Bundle?) {
            super.onCreate(savedInstanceState)
            setContentView(R.layout.activity_login)
        }

     private fun disableLoginButton(){
            button_login.isEnabled = false
     }

     private object textChangeListener: TextWatcher{

            override fun afterTextChanged(p0: Editable?) {
            }

            override fun beforeTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) {
            }

            override fun onTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) {
                //Here i cannot call function
                disableLoginButton() // unresolved reference. 
            }

        }
    }

But when i call LoginActivity().disableLoginButton() instead disableLoginButton()it's visible, but fails with

NullPointerException

on login_button

Inner objects are singletons and cannot access wrapping class instance. I have added details to my wrong answer — Mohammed Aquib Azad
– Mohammed Aquib Azad, Commented Jan 28, 2020 at 12:24

Kalpesh Rupani · Accepted Answer · 2020-01-28 12:20:28Z

2

Try this :

    class LoginActivity: AppCompatActivity(){
        override fun onCreate(savedInstanceState: Bundle?) {
                super.onCreate(savedInstanceState)
                setContentView(R.layout.activity_login)

        editTextSample.addTextChangedListener(object : TextWatcher {

                override fun afterTextChanged(s: Editable) {}

                override fun beforeTextChanged(s: CharSequence, start: Int,
                                               count: Int, after: Int) {
                }

                override fun onTextChanged(s: CharSequence, start: Int,
                                           before: Int, count: Int) {
                    disableLoginButton()
                }
            })

            }




        }

     private fun disableLoginButton(){
                button_login.isEnabled = false
         }

edited Jan 28, 2020 at 12:20

answered Jan 28, 2020 at 12:08

Kalpesh Rupani

1,0496 silver badges13 bronze badges

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5 Comments

Rarity7- Over a year ago

No, button_login doesn't visible too.

Kalpesh Rupani Over a year ago

What you have to do, you want to hide or visible button Or disable click event ?

Kalpesh Rupani Over a year ago

please paste your full activity here

Rarity7- Over a year ago

i just want to access my button from TextWatcher object, to disable it, when user starts writing on editText.

Kalpesh Rupani Over a year ago

Just apply TextWatcher on your UI component , here I mentioned editTextSample

Mohammed Aquib Azad · Accepted Answer · 2020-01-28 12:19:16Z

0

EDIT: Doesn't work

From jetbrains team:

In Java and Kotlin, "inner" means "capturing the outer instance", where as "nested" means simply declared inside something else. Java's static classes are only nested, non-static nested classes are inner. In Kotlin you have to explicitly declare something as "inner" (we reversed the Java's convention). So, your object is not inner, btu only nested. And no named object can be inner, in fact: named objects are singletons, so the can not depend on any kind of outer instance.

Try specifying the object as inner:

private inner object textChangeListener: TextWatcher{

     override fun afterTextChanged(p0: Editable?) {
     }

    override fun beforeTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) {
     }

     override fun onTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int {
          //Here i cannot call function
           disableLoginButton() // unresolved reference. 
     }
}

This should allow you to access the outer scope.

edited Jan 28, 2020 at 12:19

answered Jan 28, 2020 at 12:14

Mohammed Aquib Azad

6344 silver badges9 bronze badges

1 Comment

Mohammed Aquib Azad Over a year ago

I am sorry, I believed all inner declarations were supposed to be marked as inner explicitly

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