Android Dropdown List with Spinner

Demo

If you want implement a simple drop down list. Here you go.
Spinner is used to select one value from a set of values in Android. Android Spinner is associated with AdapterView, so that we need to set a adapter class with the Spinner.
Let’s code!

It consists of a TextView and a Spinner in the following layout file:

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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=".MainActivity"> <TextView android:id="@+id/tvSelectedItem" android:layout_width="0dp" android:layout_height="wrap_content" android:text="Hello World!" android:gravity="center" app:layout_constraintBottom_toBottomOf="parent" app:layout_constraintLeft_toLeftOf="parent" app:layout_constraintRight_toRightOf="parent" app:layout_constraintTop_toTopOf="parent" /> <Spinner android:id="@+id/spDropdownList" android:layout_width="0dp" android:layout_height="wrap_content" app:layout_constraintBottom_toBottomOf="parent" app:layout_constraintLeft_toLeftOf="parent" app:layout_constraintRight_toRightOf="parent" app:layout_constraintTop_toBottomOf="@id/tvSelectedItem"/>

</androidx.constraintlayout.widget.ConstraintLayout>

  

 

  
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Following snippet shows how to associate a adapter to Spinner:

 private fun prepareSpinnerAdapter(){ spinnerAdapter = ArrayAdapter(this@MainActivity,android.R.layout.simple_spinner_dropdown_item,spinnerDropdownList) spinnerAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item) spinner.adapter = spinnerAdapter spinner.onItemSelectedListener = object: AdapterView.OnItemSelectedListener{ override fun onItemSelected( parent: AdapterView<*>?, view: View?, position: Int, id: Long ) { tvSelectedItem.text = parent?.getItemAtPosition(position).toString() } override fun onNothingSelected(parent: AdapterView<*>?) { TODO("Not yet implemented") } } }


  

 

  
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We register a listener to Spinner. It gets the value selected by clicking.It’ll show on the TextView component.
Following code is to prepare data for Spinner:

private fun prepareDataForSpinner(){ for(i in 1 until 10){ spinnerDropdownList.add("Item $i") } }

  

 

  
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All code of MainActivity.java is here:

package com.example.dropdownlist

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.view.View
import android.widget.AdapterView
import android.widget.ArrayAdapter
import android.widget.Spinner
import android.widget.TextView

class MainActivity : AppCompatActivity() { private lateinit var tvSelectedItem: TextView private lateinit var spinner:Spinner private val spinnerDropdownList:MutableList<String> =  mutableListOf() private lateinit var spinnerAdapter:ArrayAdapter<String> override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main) spinner = findViewById(R.id.spDropdownList) tvSelectedItem = findViewById(R.id.tvSelectedItem) prepareDataForSpinner() prepareSpinnerAdapter() } private fun prepareDataForSpinner(){ for(i in 1 until 10){ spinnerDropdownList.add("Item $i") } } private fun prepareSpinnerAdapter(){ spinnerAdapter = ArrayAdapter(this@MainActivity,android.R.layout.simple_spinner_dropdown_item,spinnerDropdownList) spinnerAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item) spinner.adapter = spinnerAdapter spinner.onItemSelectedListener = object: AdapterView.OnItemSelectedListener{ override fun onItemSelected( parent: AdapterView<*>?, view: View?, position: Int, id: Long ) { tvSelectedItem.text = parent?.getItemAtPosition(position).toString() } override fun onNothingSelected(parent: AdapterView<*>?) { TODO("Not yet implemented") } } }
}

  

 

  
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文章来源: blog.csdn.net，作者：WongKyunban，版权归原作者所有，如需转载，请联系作者。

原文链接：blog.csdn.net/weixin_40763897/article/details/115461038