Key Points in Mobile App UI Design

Mobile App Design is important whether you are getting it developed for Business need or to be the next WhatsApp or Instagram.

Mobile Apps have changed the previous paradigm of having maximum features in any software applications. Mobile Apps are normally developed for a specific task and the display screen size also does not allow multiple features to be added. So designing a Mobile App may be very different from designing any other web application.
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Design is like a Joke

If it has to be explained then it's poor. Consumers have options and their time is important. They do not have time to read hints/manual in order to use your product. Much has been written about Steve Jobs obsession with Design. It is said that he visited India and was impressed by simplicity here. This affected his perspective toward Design. Average users does not like complexity or clutter.
UI Design is both Science and Arts. Users are pampered when they feel they are using a premium product. Perception of high quality comes from aesthetics. The effort that goes in building aesthetics for a UI is appreciated by users and perception of the product being premium is built in their minds.

UI Design Principles for App in short:

1.Keep it Focused
Your app should do one primary task. Trying to have lot of features in one App does not work. If a user has search for the primary task looking into menu list then your App would be most probably uninstalled.
2.Back Button should be in proper place.
Mobile App users are gen y people. They get turned off easily. Many Apps do not have back button in proper place. In Android OS native back button works but in iOS the back button has to be on left top side where the user expects.
3.Think about the Keyboard
Once the keyboard on a smartphone is activated then the App design should be such that user knows the context of his input well. Many Designers ignore the same.
4.Watch your button sizes
Mobile screen are of different sizes. According to trend of having all the buttons in the same tab many designers make buttons small. This can cause problems to users using smaller screen sizes.
5.Check Image Resolution
Many smartphones have very high screen resolution. If the image used in App development is of low pixel quality then Image may look fuzzy on such phones.