IOS中经常用到的空间尺寸大小

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 / Toolbar 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 atab bar	367 pts
Portrait Keyboard height	216 pts
Landscape Keyboard height	140 pts

Pointsvs.
Pixels
The
iPhone 4 introduced a high resolution display with twice thepixels of previous iPhones. However you don't have to modifyyour code tosupport
high-res displays; the coordinate system goes by pointsrather than pixels, and the dimensi***** in points of the screenand all UI elements remain the same.
iOS 4supports
high resolution displays (like the iPhone 4 display) viathe scale propertyon
UIScreen, UIView, UIImage, and CALayer classes. If the object isdisplaying 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 @2xversi***** of the images in your project. Seethe checklist for updating
to iOS4 or Apple documentationfor Supporting
High Resolution Screens formore
info.
Adjusting
Sizes
Click
here to see how toadjust View Frames and Bounds.
Additional
References

Apple Documentation: Points
vs. PixelsAppleDocumentation: UIBarButtonItem ClassReference says
"Typically, the size of atoolbar and navigation bar image is 20 x 20 points."AppleDocumentation: UITabBarItem
ClassReference says "The size of an tab bar imageis typically 30 x 30 points."