A blank or static screen displayed while content loads can make it seem like your app is frozen, resulting in confusion and frustration, and potentially causing people to leave your app.
Make it clear when loading is occurring. At a minimum, show an activity spinner that denotes something is happening. Even better, display explicit progress so users can gauge how long they’ll be waiting.
Educate or entertain to mask loading time. Consider showing hints about gameplay, entertaining video sequences, or interesting placeholder graphics.
Customize loading screens. Although standard progress indicators are usually OK, they can sometimes feel out of context. Consider designing a more immersive experience through custom animations and elements that match the style of your app or game.
Show screens of content as soon as possible. Don’t make people wait for content to load before seeing the screen they're expecting. Show the screen immediately, and use placeholder text, graphics, or animations to identify where content isn't available yet. Replace these placeholder elements as the content loads. Whenever possible, preload upcoming content in the background, such as while an animation is playing or the user is navigating a level or menu.
See also Progress Indicators.