Modality creates focus by preventing people from doing other things until they complete a task or dismiss a message or view. Action sheets, alerts, and activity views provide modal experiences. When a modal view appears onscreen, the user must make a choice by tapping a button or otherwise exiting the modal experience. Some apps implement modal views, such as while editing an event in Calendar or choosing a bookmark in Safari. A modal view can occupy the entire screen, an entire parent view, such as a popover, or a portion of the screen. A modal view typically includes completion and cancel buttons that exit the view.
Choose a modal transition style that makes sense in your app. Use a transition style that coordinates with your app and enhances the awareness of the temporary context shift. The default transition vertically slides the modal view up from the bottom of the screen and back down once dismissed. The flip-style transition appears to flip a view horizontally to reveal the modal view and flip back to the view when the modal view is dismissed. In this style, the modal view looks like the back of the current view. Use consistent modal transition styles throughout your app.