출처 : http://www.google.com/design/spec/patterns/launch-screens.html
For apps that have very short load times, or don’t have a strong branding need, a placeholder UI presents the fewest possible transitions and greatest perceived responsiveness.
On launch, core structural elements such as the status bar, app bar, and bottom sheets are displayed without content until the app has loaded.
Branded launch screens are a good way to portray a brand while the app is loading. Take advantage of the loading time to display your logo or other elements that improve brand recognition. Avoid using text on this screen except your logo and, if applicable, a tagline.
Launch screens should be used for initial, cold launch from the home screen, and should not displayed if the application is running, or if the launch comes from another application.
