Activity.onCreateDialog()

官網原文：

Callback for creating dialogs that are managed (saved and restored) for you by the activity. If you use showDialog(int), the activity will call through to this method the first time, and hang onto it thereafter. Any dialog that is created by this method will automatically be saved and restored for you, including whether it is showing. If you would like the activity to manage the saving and restoring dialogs for you, you should override this method and handle any ids that are passed to showDialog(int). If you would like an opportunity to prepare your dialog before it is shown, override onPrepareDialog(int, Dialog).

換言之，當某一dialog已經過onCreateDialog() create過後，下一次在call Activity.showDialog(), 就會直接進Activity.onCreateDialog()而不會再進onCreateDialog()了。