iPhone开发中经常用到这些尺寸，在这里做一下记录。
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 a tab bar??? 367 pts
Portrait Keyboard height??? 216 pts
Landscape Keyboard height??? 140 pts