How to implement a multi-select Spinner in Kotlin Android

How to implement a multi-select Spinner in Kotlin Android.

Here's a step-by-step tutorial on how to implement a multi-select Spinner in Kotlin Android:

Step 1: Set up a new Android project

• Open Android Studio and create a new project.
• Choose an appropriate project name and package name.
• Select the minimum SDK version and other project settings according to your requirements.
• Wait for the project to be created.

Step 2: Add the necessary dependencies

• Open the build.gradle (Module: app) file.
• Add the following dependency in the dependencies block:

implementation 'com.jaredrummler:material-spinner:1.3.1'

• Sync the project to download the dependency.

Step 3: Create the layout file

• Open the activity_main.xml file in the res/layout directory.
• Add the following code to create a Spinner and a Button:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="16dp"
    tools:context=".MainActivity">

    <com.jaredrummler.materialspinner.MaterialSpinner
        android:id="@+id/spinner"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Select items"
        android:padding="8dp"
        android:background="@android:drawable/btn_dropdown"
        android:dropDownHorizontalOffset="0dp"
        android:dropDownVerticalOffset="0dp"
        android:dropDownWidth="match_parent"
        android:spinnerMode="dropdown"
        android:theme="@style/SpinnerTheme" />

    <Button
        android:id="@+id/btn_submit"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/spinner"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="16dp"
        android:text="Submit" />

</RelativeLayout>

Step 4: Create a custom adapter

• Create a new Kotlin file called CustomAdapter.kt.
• Add the following code to create a custom adapter that extends ArrayAdapter:

import android.content.Context
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.ArrayAdapter
import android.widget.CheckBox
import kotlinx.android.synthetic.main.item_spinner.view.*

class CustomAdapter(context: Context, private val itemList: List<String>) :
    ArrayAdapter<String>(context, 0, itemList) {

    private val selectedItems = mutableListOf<String>()

    override fun getView(position: Int, convertView: View?, parent: ViewGroup): View {
        val view = convertView ?: LayoutInflater.from(context)
            .inflate(R.layout.item_spinner, parent, false)

        val item = itemList[position]
        view.checkBox.text = item
        view.checkBox.isChecked = selectedItems.contains(item)

        view.checkBox.setOnCheckedChangeListener { _, isChecked ->
            if (isChecked) {
                selectedItems.add(item)
            } else {
                selectedItems.remove(item)
            }
        }

        return view
    }

    fun getSelectedItems(): List<String> {
        return selectedItems
    }
}

Step 5: Implement the multi-select Spinner in MainActivity

• Open the MainActivity.kt file.
• Add the following code to implement the multi-select Spinner functionality:

import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import com.jaredrummler.materialspinner.MaterialSpinner
import kotlinx.android.synthetic.main.activity_main.*

class MainActivity : AppCompatActivity() {

    private val itemList = listOf("Item 1", "Item 2", "Item 3", "Item 4", "Item 5")

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val adapter = CustomAdapter(this, itemList)
        spinner.setAdapter(adapter)

        btn_submit.setOnClickListener {
            val selectedItems = adapter.getSelectedItems()
            // Use the selected items as needed
        }
    }
}

Step 6: Run the application

• Connect an Android device or start an emulator.
• Run the application and test the multi-select Spinner functionality.

That's it! You have successfully implemented a multi-select Spinner in Kotlin Android. The selected items can be retrieved by calling the getSelectedItems() method on the custom adapter.