How to customize the spinner?

Question

I am creating a custom spinner with a custom background as that will hide the difficult dropdown, that's why I am setting a custom layout to show the dropdown. but when I am adding the adapter to the spinner the app is crashing? why? This is the spinner code

<Spinner
        android:id="@+id/spinner"
        android:layout_width="300dp"
        android:layout_height="40dp"
        android:layout_marginTop="70dp"
        android:padding="10dp"
        android:background="@drawable/border"
        android:spinnerMode="dropdown"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.5"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"/>

This is drawable border

<shape xmlns:android="http://schemas.android.com/apk/res/android">
    <stroke android:color="@color/text" android:width="1dp"/>
    <corners android:radius="15dp"/>

</shape>

this is the custom layout ---list_item.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <ImageView
        android:id="@+id/imageViewDropdown"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/dropdown"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintBottom_toBottomOf="parent"/>

    <TextView
        android:id="@+id/textViewItem"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:textSize="20sp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toStartOf="@id/imageViewDropdown"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintBottom_toBottomOf="parent"/>

</androidx.constraintlayout.widget.ConstraintLayout>

This is my fragment code

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        val spinner=binding.spinner
        val spinnerAdapter = ArrayAdapter(
            requireContext(),
            android.R.layout.simple_dropdown_item_1line,
            this.listitem
        )//this is working fine
//        val spinnerAdapter = ArrayAdapter(
//            requireContext(),
//            R.layout.list_item,
//            this.listitem
//        ) This is I wanted to do 
        spinner.adapter = spinnerAdapter
    }

The error I am getting

 Caused by: java.lang.ClassCastException: androidx.constraintlayout.widget.ConstraintLayout cannot be cast to android.widget.TextView


Process: com.example.assignmentbackcoffer, PID: 32542
java.lang.IllegalStateException: ArrayAdapter requires the resource ID to be a TextView

I don't wanted to change the border effect. This is very important to me , I will be very happy if someone help me, Thanks in advance.

Answer 1

Please pay attention to ArrayAdapter data type. It has only String, but you give him layout which contains text and image when it expects only string. Default ArrayADapter does not know how to process it. This code from this SO answer should work:

Spinner              spinnerCountShoes = (Spinner)findViewById(R.id.spinner_countshoes);
ArrayAdapter<String> spinnerCountShoesArrayAdapter = new ArrayAdapter<String>(
                     this,
                     android.R.layout.simple_spinner_dropdown_item, 
                     getResources().getStringArray(R.array.shoes));
spinnerCountShoes.setAdapter(spinnerCountShoesArrayAdapter);

Please check out this answer for details on how to implement use case you asked.