Points vs. Pixels
Element Size (in points) Window (including status bar) 320 x 480 pts Status Bar
(How to hide the status bar)
20 pts View inside window
(visible status bar)
320 x 460 Navigation Bar 44 pts Nav Bar Image /
up to 20 x 20 pts (transparent PNG) Tab Bar 49 pts Tab Bar Icon up to 30 x 30 pts (transparent PNGs) Text Field 31 pts Height of a view inside
a navigation bar
416 pts Height of a view inside
a tab bar
411 pts Height of a view inside
a navbar and a tab bar
367 pts Portrait Keyboard height 216 pts Landscape Keyboard height 140 pts
The iPhone 4 introduced a high resolution display with twice the pixels of previous iPhones. However you don't have to modify your code to support high-res displays; the coordinate system goes by points rather than pixels, and the dimensions in points of the screen and all UI elements remain the same.
iOS 4 supports high resolution displays (like the iPhone 4 display) via the scale property on UIScreen, UIView, UIImage, and CALayer classes. If the object is displaying high-res content, its scale property is set to 2.0. Otherwise it defaults to 1.0.
All you need to do to support high-res displays is to provide @2x versions of the images in your project. See the checklist for updating to iOS4 or Apple documentation for Supporting High Resolution Screens for more info.
Click here to see how to adjust View Frames and Bounds.