setBackgroundColor recycleView in fragment

Question

I have trying to setBackgroundColor recycleView in fragment like in tutorial.

override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,
                          savedInstanceState: Bundle?): View? {

    recycleViewRandom.setBackgroundColor(Color.BLUE)

    return inflater.inflate(R.layout.fragment_recycle_view, container, false)
}

and here is my xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".fragments.MainFragment">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/recycleViewRandom"
        android:layout_width="368dp"
        android:layout_height="495dp"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginRight="8dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="1.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="1.0" />
</android.support.constraint.ConstraintLayout>

everything looks good, same as in tutorial, but I have got from IDE:

setBackgroundColor(int)' on a null object reference

How is it possible that is null ?

it's not duplicate, your link is about java, not Kolitn :) – jackfield May 12 '18 at 10:27 — jackfield, May 12 '18 at 10:27

IntelliJ Amiya · Accepted Answer · 2018-05-12T10:33:04.950

0

NullPointerException is thrown when an application attempts to use an object reference that has the null value.

Declare

 lateinit var                            recycleViewRandom: RecyclerView

Then

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

You should Initialize RecyclerView.

    fun initUI(contentView: View)
    {
        recycleViewRandom= contentView.findViewById(R.id.recycleViewRandom)
        recycleViewRandom.setBackgroundColor(Color.BLUE)
     }

edited May 12 '18 at 10:33

answered May 12 '18 at 10:24

IntelliJ Amiya

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can you describe this ? – jackfield May 12 '18 at 10:25
ok thank I know what is npe, but why this need "initUI" ? – jackfield May 12 '18 at 10:27
@jackfield Initialize RECYCLERVIEW into `initUI` section. – IntelliJ Amiya May 12 '18 at 10:27
@jackfield npe stands for `NullPointerException`. I have already described . – IntelliJ Amiya May 12 '18 at 10:30
content view should be initialize with var first ? – jackfield May 12 '18 at 10:32
1

ok, work, thanks, but contentView should be also initialize "var" ? – jackfield May 12 '18 at 10:38
@jackfield you can. – IntelliJ Amiya May 12 '18 at 10:39

setBackgroundColor recycleView in fragment

1 Answers1