Why does btnOpen return null when I invoke it on onCreateView with Kotlin?

Asked Nov 21 '18 at 08:27

Active Nov 21 '18 at 08:36

Viewed 38 times

I get the error information

 Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference

when I run the code btnOpen.setOnClickListener.

But the system is OK when I run the code

var s= rootView.findViewById<Button>(R.id.btnOpen)

why?

Code

import kotlinx.android.synthetic.main.layout_tab_clipboard.*

import info.dodata.clipboard.R
import utility.openActivity

class UITabClipboard: Fragment(){
    private lateinit var  mContext: Context

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
        val rootView = inflater.inflate(R.layout.layout_tab_clipboard, container, false)
        mContext = rootView.context

        var s= rootView.findViewById<Button>(R.id.btnOpen) //It's OK
        s.setOnClickListener(){
            mContext.openActivity<UIAbout>()
        }     


        btnOpen.setOnClickListener {           //It cause error
            mContext.openActivity<UIAbout>()
        }

        return rootView
    }


}

edited Nov 21 '18 at 08:36

Sarath Kn

2,680
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asked Nov 21 '18 at 08:27

HelloCW

Use it inside `onActivityCreated` method and check – Manohar Nov 21 '18 at 08:30
shouldn't you be using `val` instead of `var` – karan Nov 21 '18 at 08:31
2

`onCreateView()` is too early. You can only use synthetic view refs after `onCreateView()` in the fragment lifecycle. https://stackoverflow.com/questions/34541650/nullpointerexception-when-trying-to-access-views-in-a-kotlin-fragment – laalto Nov 21 '18 at 08:31
`btnOpen` is `NULL`. – Martin Zeitler Nov 21 '18 at 08:32
Thanks! But why is `var s= rootView.findViewById – HelloCW Nov 21 '18 at 08:37
1

@HelloCW because it's not accessed as a synthetic view. – Martin Zeitler Nov 21 '18 at 08:40

Why does btnOpen return null when I invoke it on onCreateView with Kotlin?

0 Answers0