The user interface of iOS (iPhone/iPad) is one of the key things of its success.
If you own an iPhone or an iPad you probably know how it’s easy to understand a new app.
A reason is that Apple provide a set of rules and advices on how to design the user interface.
All these rules are compiled in the document Human Interface Guidelines(PDF).
This document is a must-read before starting iPad or iPhone development.
Three examples of advices :
Think twice before you redesign a standard control
An iPhone user is used to native iOS controls such as the title bar, tool bar, etc.
That’s also true for the size of these controls. Each button have the size of a fingerprint, which is the best size for a touch device.
Our instinct requires to feel a feedback in response of our actions. For instance pushing a button will give a feedback to your finger.
This is not possible for a touch device. That’s why your app have to provide a visual feedback each time the user do an action.
Look closer at a UITableView, the bouncing animation when you reach the end is a feedback that there is nothing more.
When we discover something new, we use our previous experiences to guess how to use it.
If you see a button on an object, you know it can be pushed and you know that something will happen.
You can even guess if its a good(gree) or bad(red) thing depending of the color of the button.
If you open the contact app on iPad, you instantaneously understand how it works because it looks like a real contact book.
The point here is that out brain can handle less that eight information units at a time.
User interface design is really complex and require specific competences to understand how the user think.