Once your ListView has reached the max amount of rows it can display on a screen, Android is smart enough to begin recycling those row Views. If it is not null then we have a recycled View and can just change its values, otherwise, we need to create a new row View. The magic behind this is the setTag method which lets us attach an arbitrary object onto a View object, which is how we save the already inflated View for future reuse.
Customizing Android ListView Rows by Subclassing describes a strategy for obtaining instances of child views using a similar approach as a ViewHolder but without the explicit ViewHolder subclass. Jump to Section. Edit Page Page History. The ArrayAdapter fits in between an ArrayList data source and the ListView visual representation and configures two aspects: Which array to use as the data source for the list How to convert any given item in the array into a corresponding View object Note as shown above that there are other data sources besides an ArrayAdapter such as the CursorAdapter which instead binds directly to a result set from a Local SQLite Database.
Row View Recycling When using an adapter and a ListView , we need to make sure to understand how view recycling works. Here is a visual overview of recycling: Here is another related diagram on view recycling: Refer to this ListView guide for another look at how this works to optimize the performance of your lists.
Using a Custom ArrayAdapter When we want to display a series of items from a list using a custom representation of the items, we need to use our own custom XML layout for each item. Populating Data into ListView Once the adapter is attached, items will automatically be populated into the ListView based on the contents of the array. You can also clear the entire list at any time with: adapter. Unlike ListView, RecyclerView enforces the use of the ViewHolder pattern and is much more flexible in terms of layout and animation.
Feel free to share your feedback, findings or ask any questions in the comments below or in the forums. Talk to you soon! The raywenderlich. Get a weekly digest of our tutorials and courses, and receive a free in-depth email course as a bonus! Learn iOS, Swift, Android, Kotlin, Dart, Flutter and more with the largest and highest-quality catalog of video courses and books on the internet.
He started as a web Odie recently completed an undergraduate degree in Software Engineering and is a postgrad student at the University of East A raywenderlich. Start Reading. Note: You should never perform long-running tasks on the main thread. When you do, you expose yourself to the risk of blocking the UI, and that would make scrolling your lists a nightmare! Note: To learn more about intents, check out the awesome Android Intents Tutorial.
Download Materials. Sign up now Website. Average Rating 4. Add a rating for this content Sign in to add a rating. All videos. All books. One low price. Learn more. Mark Complete Clear Progress. Completed New. These changes will be reflected in your model. The ExpandableListView is similar to ListView , but allows you to define groups and details for this group.
In this case you have to define two layouts, one for the group and another one for the details row. Create a project called com. Create the following class which holds your domain model for the ExpandableListView. Finally create the adapter as described by the following listing and change the activity to the code provided below.
You can of course put arbitrary views elements around your list view. For example you can define a layout with two text views and a list view between them.
In this case the two text views will always be visible above the list header and the other will be visible below the list. If you want to display a list header or list footer only at the beginning or end of the list you can use the addHeaderView method or addFooterView method on the ListView class. In case you work with a content provider or directly with the database you can use the SimpleCursorAdapter to define the data for your ListView. The following will demonstrate how to access the Contacts ContentProvider.
Create a new Android project called "de. Change MyListActivity to the following. Make sure you give your application the permission to read the contacts Uses Permissions "android. Sometimes having to press a refresh button on the ActionBar to refresh data can be annoying for the user. Chris Banes has implemented an Open Source library to implement the pull to refresh pattern for a Listview.
Also you may want to use the swipe to dismiss gesture to delete items from a ListView. ListView demo which uses 3D effects GitHub. Google documentation about RecyclerView. ListView demo which uses 3D effects Github. Free use of the software examples is granted under the terms of the Eclipse Public License 2. Sponsor our Open Source development activities and our free content to help us make development easier for everyone. This tutorial describes how to use ListView together with activities and fragments in Android.
Using lists in Android The display of elements in a list is a very common pattern in mobile applications. Android and the ListView widget 2. Views for handling lists Android provides the ListView and the ExpandableListView classes which are capable of displaying a scrollable list of items. Possible input types for lists The input of a list items in the list can be arbitrary Java objects.
Adapters An adapter manages the data model and adapts it to the individual entries in the widget. Filtering and sorting The filtering and sorting of the data is handled by the adapter. Data updates in the adapter The notifyDataSetChanged method on the adapter is called if the data has changed or if new data is available. Default adapter 3. Default platform adapter Android provides default adapter implementations; the most important are ArrayAdapter and CursorAdapter.
If you want to change the data in your adapter, the underlying data structure must support this operation. This is, for example, the case for the ArrayList class, but not for arrays. Custom adapter implementations 4. Developing a custom adapter The ArrayAdapter is limited as it supports only the mapping of toString to one view in the row layout.
Frequently you extend ArrayAdapter to write a custom adapter, as this is simpler than extending BaseAdapter directly. Preparing a row for the list The adapter needs to create a layout for each row of the list. This layout inflator service can get accessed via the getLayoutInflator method of the activity or via the context.
Example for a custom adapter The following code shows an implementation of a custom adapter. Context ; import android. LayoutInflater ; import android. View ; import android.
ViewGroup ; import android. ArrayAdapter ; import android. ImageView ; import android. Updating the data model from the adapter The row can also contain views which interact with the underlying data model via the adapter. ListActivity and ListFragment 5. Default container for using ListView Android provides specialized fragment and activity classes to simplify list handling.
The following example code shows a simple ListFragment implementation. Intent ; import android. Bundle ; import android. ListView ; import android. The next example code demonstrates the usage of a ListActivity. ListActivity ; import android. If you do not use this ID or do not include a ListView into your layout, the application crashes once you try to display the activity or the fragment. Exercise: ListActivity with custom layout In our example your will define your layout for the rows and use it in your adapter.
Tutorial: Implementing your customer adapter The following uses two images "no. Create the class MySimpleArrayAdapter which will serve as our adapter. If you run this example you should get a list with different icons for the certain elements.
ListViews and performance 9. Motivation Performance is especially important on Android as users expect fast reaction times. Now we just bind the array list items to the row layout by using mylistview. Per Arvand: Eclipse: Simply type android. Stack Overflow for Teams — Collaborate and share knowledge with a private group.
Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. What is "android. Ask Question. Asked 11 years, 2 months ago. Active 4 years, 6 months ago. Viewed k times. Improve this question. Alexander Farber Zakaria Zakaria But why is that a parameter?
I just wanted to update my listview with my array, and one of the answers showed this. I am not sure why I need this
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