iPhone 尺寸

Element	Size (in pixels)
Window (including status bar)	320 x 480px
Status Bar (How to hide the status bar )	20 px
View inside window  (visible status bar)	320 x 460
Navigation Bar	44 px
Nav Bar Image / Toolbar Image	up to 20 x 20 px (transparent PNG)
Tab Bar	49 px
Tab Bar Icon	up to 30 x 30 px (transparent PNGs)
Text Field	31 px
Height of a view inside  a navigation bar	416 px
Height of a view inside  a tab bar	411 px
Height of a view inside  a navbar and  a tab bar	367 px
Portrait Keyboard height	216 px
Landscape Keyboard height	140 px