keyboardType="numeric"
returnKeyType="search"/>
决定返回键的样式：
returnKeyType enum('default', 'go', 'google', 'join', 'next',
'route', 'search', 'send', 'yahoo', 'done', 'emergency-call')
决定打开哪种键盘，例如，数字键盘：
keyboardType enum('default', "ascii-capable",
'numbers-and-punctuation', 'url', 'number-pad', 'phone-pad',
'name-phone-pad', 'email-address', 'decimal-pad', 'twitter',
'web-search', "numeric")
