如何使用Kotlin在Android Studio上正确设置SwipeRefreshLayout？

Question

I'm trying to use a SwipeRefreshLayout on my project, but there's something wrong... and I don't know what! Below I show the kotlin code, XML and the error I'm getting.

NOTE, it's a FRAGMENT

KOTLIN CODE:

override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        swipeRefresh.setOnRefreshListener {
            refreshAction() // refresh your list contents somehow
            swiperefresh_saloes.isRefreshing = false
        }
}

XML CODE

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        app:layout_behavior="@string/appbar_scrolling_view_behavior"
        tools:context=".Activities.Fragments.SaloesFragment">

        <android.support.v4.widget.SwipeRefreshLayout
                android:id="@+id/swipeRefresh"
                xmlns:android="http://schemas.android.com/apk/res/android"
                android:layout_width="fill_parent"
                android:layout_height="fill_parent">

        <android.support.v7.widget.RecyclerView
                android:id="@+id/recyclerViewSaloes"
                android:scrollbars="vertical"
                android:layout_width="match_parent"
                android:layout_height="match_parent"/>

        </android.support.v4.widget.SwipeRefreshLayout>

</RelativeLayout>

but I'm getting the following error:

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v4.widget.SwipeRefreshLayout.setOnRefreshListener(android.support.v4.widget.SwipeRefreshLayout$OnRefreshListener)' on a null object reference at com.zowye.b2b.Activities.Fragments.SaloesFragment.onCreate(SaloesFragment.kt:69)

Answer 1

I found the error: Since it's a fragment, I can only access the SwipeRefreshLayout after onCreateView inflates the fragment.

So, I setted the listener inside onViewCreated

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {

        swipeRefresh.setOnRefreshListener {
            refreshAction()                    // refresh your list contents somehow
            swipeRefresh.isRefreshing = false   // reset the SwipeRefreshLayout (stop the loading spinner)
        }

    }

Answer 2

OnCreate calls before onCreateView.your view is yet not present when you are calling swipe refresh . Instead put a check before calling this method ie if(activity != null) . And in onCreateView of fragment , provide the view to fragment . Then call this method

    override fun onCreateView(inflater: LayoutInflater, 
                            container: ViewGroup?, 
                            savedInstanceState: Bundle?): View? {
    return inflater.inflate(R.layout.fragment_dog_details, container, false)
  }