#Listview android studio series
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. If the app requires a more complex translation between item and View then we need to create a custom ArrayAdapter instead. setAdapter ( itemsAdapter ) īy default, this will now convert each item in the data array into a view by calling toString on the item and then assigning the result as the value of a TextView ( simple_list_item_1.xml) that is displayed as the row for that data item. Now, we just need to connect this adapter to a ListView to be populated: ListView listView = ( ListView ) findViewById ( R. Note that we've chosen simple_list_item_1.xml which is a simple TextView as the layout for each of the items. The ArrayAdapter requires a declaration of the type of the item to be converted to a View (a String in this case) and then accepts three arguments: context (activity instance), XML item layout, and the array of data. First, we initialize the adapter: ArrayAdapter itemsAdapter = new ArrayAdapter ( this, android. To use a basic ArrayAdapter, you just need to initialize the adapter and attach the adapter to the ListView. Tool, which provides a graphical way of visualizing the layout performance. If you wish to evaluate how fast your ListView is rendering, check out the Profiling GPU Be sure to check out this Udacity video on view recycling as well. Refer to this ListView guide for another look at how this works to optimize the performance of your lists. Here is another related diagram on view recycling: In this way, even for a list of 1000 items, only ~7 item view rows are ever instantiated or held in memory. Instead, as the user scrolls through the list, items that leave the screen are kept in memory for later use and then every new row that enters the screen reuses an older row kept around in memory. At that point, no additional row items are created in memory.
#Listview android studio full
When your ListView is connected to an adapter, the adapter will instantiate rows until the ListView has been fully populated with enough items to fill the full height of the screen.
When using an adapter and a ListView, we need to make sure to understand how view recycling works. 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.
#Listview android studio how to
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