Listview setonitemclicklistener android kotlin

Ничего не выделено и нажат пункт с позицией 3.

Давайте добавим к списку еще один обработчик:

OnScrollListener – обрабатывает прокрутку списка.

view – это прокручиваемый элемент, т.е. ListView
scrollState – состояние списка. Может принимать три значения:

SCROLL_STATE_IDLE = 0, список закончил прокрутку
SCROLL_STATE_TOUCH_SCROLL = 1, список начал прокрутку
SCROLL_STATE_FLING = 2, список «катнули», т.е. при прокрутке отпустили палец и прокрутка дальше идет «по инерции»

Вывод в лог я пока закаментил, чтобы не мешалось. Чуть позже раскаментим.

view – прокручиваемый элемент
firstVisibleItem – первый видимый на экране пункт списка
visibleItemCount – сколько пунктов видно на экране
totalItemCount – сколько всего пунктов в списке

Причем для параметров firstVisibleItem и visibleItemCount пункт считается видимым на экране даже если он виден не полностью.

Все сохраним и запустим.

Теперь потаскайте список туда-сюда курсором (как будто пальцем) и смотрите логи. Там слишком много всего выводится. Я не буду здесь выкладывать. Но принцип понятен – меняется первый видимый пункт (firstVisibleItem) и может на единицу меняться кол-во видимых пунктов (visibleItemCount).

Теперь закоментируем вывод в лог в методе onScroll (чтобы не спамил нам лог) и раскаментим в onScrollStateChanged.

Схватим список, немного потягаем туда сюда и отпустим. Смотрим лог:

scrollState = 1
scrollState = 0

Отработали два события – список начал прокрутку, список закончил прокрутку.

Попробуем взять список, «катнуть» его и отпустить.

scrollState = 1
scrollState = 2
scrollState = 0

Видим три события – прокрутка началась, список «катнули», прокрутка закончилась.

Полный код урока:

На следующем уроке:

— строим список-дерево ExpandableListView

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Listview setonitemclicklistener android kotlin

Android Kotlin ListView Example

It is very common in most of the applications that a list of data items is displayed in UI. In android applications, list of data items can be shown to users using ListView.

Data items in various types of applications which are displayed as list in UI are list of categories or products in shopping app, list of search results in apps with search functionality, list of articles in blog apps, list of tourist attractions in tourism related apps, list of movies, list of audio, etc.

Android ListView displays data vertically with each item positioned below the previous data items. ListView is scrollable. You can use ListView without any issues for displaying few data items in UI. But for displaying large volumes of data as list, you need to use RecyclerView to build well performing apps.

Table of Contents

ListView Adapter

ListView uses adapter object to display data. ListView adapters are implementations of ListAdapter interface. ListView adapters take list of data items and item layout to be used for each item as input. Once adapter object is crated, it needs to be passed to ListView object by calling setAdapter() method.

Android provides ArrayAdapter and CursorAdapter. ArrayAdapter can be used to display array of items in ListView. CursorAdapter is used for displaying data from Cursor in ListView.

Custom ListAdapter can be created by extending BaseAdapter or its subclasses and implementing getView and other methods. We will see how to create custom listview adapter in the following sections.

Steps to Use ListView

First you need to add ListView to layout of the activity or fragment which is responsible for displaying the list screen.

In the activity, obtain the ListView object.

Then get list of data from local or remote data base and pass it to list view adapter instance. For examples list of strings can be shown in ListView using ArrayAdapter. Item layout simple_list_item_1 contains TextView which displays string item.

Then pass the adapter object to the ListView by calling setAdapter method.

Custom ListAdapter

To display complex data items meaning data list containing items with each item having several properties, custom list adapter needs to be created. You can create custom ListAdapter by extending ArrayAdapter or BaseAdapter.

In the getView method, using the item position argument passed to it, you need to get data item for that position, then inflate item layout and populate the views in item layout with the data from the data item.

Following Kotlin code shows how to create custom ListAdapter.

View Holder

The custom adapter shown above uses view holder object to avoid findViewById calls if view object exists for the position passed to getView method.

View holder object contains all the views of an item. View holder object is saved as tag in the parent view of item layout when it is created first time. In the getView method, if the view passed to it is not null, you can get the view holder object from the view and access the views of item.

Styling ListView

By styling the views of item layout used for displaying data items, you can make the look and feel of the ListView to match your apps theme. To differentiate each item in the list in terms of style, you can use different color, font, text size, etc for items in different positions and apply them in the listadapter to views of the items.

For example, you can assign a different text color to TextView of an item at a particular position in the list in the getView method of listadapter.

You can configure item divider height by setting the height on ListView object.

ListView Handling Events

If your app needs to respond when an item in the list is clicked to show details of the item clicked or take some action, you need to handle item click events by adding OnItemClickListener to list view as shown below.

If you need to track and respond to the events of views in items, you need to handle those events in the list adapter by adding appropriate event handler to the views of items. For example, following code adds OnClickListener to image view.

ListView Kotlin Example

The ListView Kotlin Example displays a list of tourist attractions of a selected place.

Main Activity

List Activity

List Activity Layout

Item Layout

Data Object

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Android app development tutorials and web app development tutorials with programming examples and code samples.

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Kotlin Android ListView Example

Kotlin Android ListView Example

Android ListView is used to display items of an array as a scrollable list.

In this tutorial, we shall learn how to display elements of an array using Android ListView with the help of a Kotlin Android Application.

We shall proceed further by adding ListView Item Click Listener so that a particular action would be taken when a click is made on an item in ListView.

An example ListView widget in Android screen would look as show in the following screenshot.

Example – Android ListView Example

Create a Kotlin Android Application with Empty Activity and follow the steps provided below to implement Android ListView. We shall use MainActivity , that is created by default while creating project, to implement ListView.

The structure of the project with MainActivity.kt and layout files is

Steps to display items of an array as Kotlin Android ListView

Step 1: Create ListView in activity_main.xml layout file.

android/res/layout/activity_main.xml

Step 2: Have an array of elements, in the MainActivity.kt class file, to be displayed as ListView.

Step 3: Create a resource under android/res/layout that could be used for each element of the array while displaying in ListView.

android/res/layout/listview_item.xml

Step 4: Initialize an Adapter (ArrayAdapter) with application context, resource to be used as View for each element of the list, and the array of elements itself as arguments.

Step 5: Set the adapter created in the previous step to the ListView.

Assembling all these steps, content of MainActivity.kt file would be as shown in the following.

MainActivity.kt

Run the Kotlin Android ListView Example Application. Following would be the output.

If you observe, ListView is by default scrollable.

Implementing ListView Item Click Listener

Now we shall implement ListView Item Click Listener to trigger execution of a specific code when an item is clicked. For this example, we shall display item position and text with Toast.

MainActivity.kt

Run this Android Application, and a list of items would be displayed as a ListView. Now, if user clicks on any of the item, its position is displayed, since we have set onItemClickListener for the ListView.

Conclusion

In this Kotlin Android Tutorial – Android ListView Example, we have learnt how to diaplay array elements in a ListView with the help of ArrayAdapter and to set ListView Item Click Listener with Example Kotlin Android Application.

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Android ListView using Kotlin

Android Tutorial

In this tutorial, we’ll implement ListView in our Android apps using Kotlin.

What is Android ListView?

ListView is a very common UI element in Android Applications. It is used to display a list of items separated by dividers that can be scrolled endlessly. It’s generally used to display a group of related items.

ListView XML Layout

ListView XML attributes

• android:divider : Drawable or color to draw between list items.
• android:divider : Drawable or color to draw between list items.
• android:dividerHeight : Height of the divider.
• android:entries : An array resource can be passed here to be displayed as a List.
• android:footerDividersEnabled : When set to false, there will be no divider at the end of the ListView.
• android:headerDividersEnabled : When set to false, there will be no divider at the top of the ListView
• android:clickable : This makes the ListView rows clickable. If you’re setting the ListView from the Activity, setting this attribute is not neccessary
• android:listSelector : Set the background color of the list view row when it is clicked.

We can populate entries in the ListView without any Java code by defining an array in the strings.xml file:

Now the ListView is populated in the layout as:

Setting the width to wrap_content wraps the ListView rows to its content.

Setting Selectors and Divider Color in ListView

Use the following ListView tag:

The above code makes the ListView selectable. But to add logic on each ListView row click we need to use the Adapter.

ListView Adapter

A ListView class by itself cannot populate the entries. An Adapter is responsible for populating the data in the ListView. We have built-in adapter classes(like the one above) which come with a built-in layout for each row. We can create our own Custom Adapter classes as well.

The adapter comes with its own set of built-in methods. Following two are the most important ones:

1. getView() : We can inflate our own layouts in the Adapter inside this method.
2. notifyDataSetChanged() method on the adapter is called if the data has changed or if new data is available.

To set the adapter on the ListView, we use the method setAdapter() .

Types of ListView Adapters

There are four main types of Adapters:

1. BaseAdapter – As the name suggests this abstract is extended by all the other adapters. When creating a custom adapter using this as the parent class, you need to override all the methods mentioned above along with getCount() , getId() etc.
2. ArrayAdapter – This populates the ListView with the array supplied. It is defined as:

The first parameter is the context, followed by the layout resource for the list rows.
The layout must have a TextView. The third parameter is the array.

For the ArrayAdapter you need to override the getView() method only. getCount() isn’t necessary since ArrayAdapter calculates the size of the array on its own.

ListView Kotlin Project Structure

1. XML Layout Code

The code for the activity_main.xml layout is given below:

2. Main Activity Kotlin Code

The code for the MainActivity.kt class is given below.

In the above code, we display a toast message. We arrived at that shorthand Toast function by adding the Anko commons dependency in our build.gradle .

resources.getStringArray(R.array.Colors) converts the string array stored in the resources file into a Kotlin Array.

android.R.layout.simple_list_item_1 is a built-in layout which hosts a TextView only.

setOnItemClickListener is the Kotlin function that gets triggered when any ListView row is clicked. Here we can implement our logic.

The four arguments inside the function are:

• adapterView : The parent view where the selection happens. Its ListView here.
• view : The selected view (row) within the ListView
• position : The position of the row in the adapter. This is an Int.
• id : The row id of the selected item. This is a Long.

Instead of retrieving the value using the array, we can get it from the adapterView as:

getItemAtPosition returns the List View Row at that index. The row is a TextView in this case.

The output of the application in action is given below:

We can change the default item press color by creating a selector drawable inside the drawable folder.

Add the following attribute inside the ListView XML Tag:

You can download the project from the below link.

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