Drop down lists for iPhone: rolling your own

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If like me, you’re fairly new to iPhone development, you might be wondering how to implement drop down lists in your app. The fact of the matter is that there is no native control provided by Apple, similar to the <select> tag
you’ll know well if you have a background in web development. So, the solution is to roll our own: stick with me for a few minutes – I promise it’s not as tricky as it sounds. Here is how our finished control will look:







We’re going to use a UIButton control with a custom background image and put a label on top of it to show the currently selected option. Go ahead
and add a UIButton and a UILabelto
your view using the Interface Builder. If you’re not much of a designer, leave the background image for now and just use a regular button – it doesn’t really matter to get the code working as we need it.

Add an IBOutlet for your label to your view controller’s header file and implement theUIPickerViewDelegate and UIPickerViewDataSource delegates.
We also need to define an NSMutableArray, a UIActionSheet and
an NSInteger – We’ll deal with these and the delegates we are implementing in just a second. Lastly, declare an IBActionshowSearchWhereOptions which
we need to connect to our button in the Interface Builder. Our finished header file looks like this:

Next – on to our implementation file. Implement the following methods that are required because of the delegates we have implemented.

Most of the work happens here.. In our showSearchWhereOptions method, which runs when the user taps our “button” (it is a button really, but
it’s sneakily pretending to be a drop down list control).

We haven’t yet defined our list items – we’ll do this in our viewDidLoad method. We need to make sure we set a default search option too. It’s
a zero based index, so setting it to 0 will make “Specified location” our default selection.

One last thing – implement the dismissActionSheet method which is responsible for hiding the action sheet when we click the done button.