#Android studio listview from text to relativelayout how to
#Android studio listview from text to relativelayout full
#Android studio listview from text to relativelayout android
#Android studio listview from text to relativelayout code

#Android studio listview from text to relativelayout code

The encapsulation it offers allows you to freely customize your list row view without your Adapter or other code having to worry about the details, and the performance should be equally as good as the holder pattern during view reuse. The next time you find yourself reaching for the holder pattern, consider subclassing instead. There are no extra “holder” classes or objects created during the process. The ItemView can be created easily in code or in an XML layout file.Īny future customizations or configuration-specific changes to the layout of ItemView can be handled entirely within that class’ implementation and layout files. The Adapter implementation is greatly simplified. While we had to create two layout files (instead of one) and a static convenience method for inflation, look at all the advantages we get for it: That’s about all there is to this pattern. After that is done, we call our private setupChildren() method to wrap up the work of calling findViewById(int) and associating the child views with the appropriate member variables. The root element is a merge tag, which means that during inflation, each of the children of that tag will be added as children of the parent argument passed to the inflate(.) method in the constructor.

Item is the generic model object that represents data within our list using three properties: an image URL, a title and a description.

#Android studio listview from text to relativelayout how to

Instead of creating a generic view, a holder class and an Adapter implementation that knows too much about how to wire them all together, we will use a subclass of RelativeLayout for the root view of our custom layout. So, rather than complaining about it all the time, I’ll propose an alternative: subclassing! Customizing Using a Subclass It violates encapsulation, since the adapter/holder has to know about the internals of the view representing each item in the list. The view’s tag property requires casting to the correct holder type, which feels kludgy. The “holder” class is typically just boilerplate code and creating it/setting it up is a chore. It puts too much responsibility in the Adapter’s getView(.) method. I don’t like this pattern, for several reasons: Reuse (and cast) the holder object for reused row views. Set the instance of the holder as the top-level view’s tag with setTag(Object). One implementation you see described all over the Internet is called “the holder pattern.” In a nutshell, it entails these steps:Ĭreate a “holder” class with fields to store child views of the row.įor each new inflated row, create a holder instance and assign its fields to the results of calling findViewById(int) for each child view. Since this is such a common problem, patterns have emerged. Take advantage of view recycling when scrolling.Įfficiently identify and populate child views with data. Use a custom layout to define the arrangement of child views. When creating custom views for a ListView or other AdapterView, we have a few requirements:

You can find the code for this example project on GitHub. You can see what it looks like in the screen shot below. The Goalįor demonstration purposes, we’ll create a typical simple custom ListView row with an ImageView and two TextViews arranged inside a RelativeLayout parent. In this post, we explore an alternative that uses a subclass of RelativeLayoutto encapsulate the customization work.

#Android studio listview from text to relativelayout full

But the Holder pattern is clumsy and full of boilerplate, and we can do better. When that happens, you’ll probably reach for the Holder pattern.

#Android studio listview from text to relativelayout android

Every Android programmer will at some point customize a ListView row by creating their own layout and populating it with data.