Wednesday, February 9, 2011

[android-developers] showDialog(int id) vs dialog.show()

Hi all,

I recent ran across this question on StackOverflow which has no real valid response or perhaps best practice. I am pasting the question below for your convenience:

As far as I can tell, there are two ways to show a Dialog from an Activity.
  1. Create the Dialog (for example, using an AlertDialog.Builder), and then call the newly created Dialog's show() method.
  1. Call the Activity's showDialog() method, passing in an int that uniquely defines what sort of Dialog you want to build. Then override onCreateDialog() to actually build the Dialog, and Android will display it for you.
The second method seems to be the standard practice but I'm curious if there is any reason it matters which one I use. Here's all I can come up with:
Reasons to use Dialog.show
  1. If you need to parameterize the Dialog in some way, it can be a little awkward to useActivity.showDialog, as described in this question. You may have to store a String or something in a member variable, just so that it can be retrieved moments later during onCreateDialog oronPrepareDialog.
  1. The logic for creating and modifying the dialog is spread out across a number of places, potentially making the code harder to read and maintain:
  • The place where you call showDialog()
  • Inside a potentially large switch statement in the overridden onCreateDialog method
  • Inside a potentially large switch statement in the overridden onPrepareDialog method
Reasons to use Activity.showDialog:
  1. The API docs for Activity.showDialog say that the Dialog is "managed" by the Activity which I suppose provides some benefit? But this is also true if you use the AlertDialog.Builder, I would think, because you pass in this as an argument to the Builder's constructor.
  1. If your Activity is going to show the same (or a very similar) Dialog several times, this option creates it only once, instead of creating a new one each time, thus putting less strain on the system as far as allocating space for new objects, garbage collection, etc.
So my question is, what are the criteria for deciding when to use Activity.showDialog and when to use Dialog.show, and why?

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