UITextField *text = [[UITextField alloc]initWithFrame:CGRectMake(20, 20, 130, 30)];  //初始化textfield并设置位置及大小

text.keyboardType = UIKeyboardTypeNumberPad;   //设置键盘的样式

typedef enum {
    UIKeyboardTypeDefault,       默认键盘，支持所有字符         
    UIKeyboardTypeASCIICapable,  支持ASCII的默认键盘
    UIKeyboardTypeNumbersAndPunctuation,  标准电话键盘，支持＋＊＃字符
    UIKeyboardTypeURL,            URL键盘，支持.com按钮 只支持URL字符
UIKeyboardTypeNumberPad,              数字键盘
UIKeyboardTypePhonePad,    电话键盘
    UIKeyboardTypeNamePhonePad,   电话键盘，也支持输入人名
UIKeyboardTypeEmailAddress,   用于输入电子 邮件地址的键盘     
UIKeyboardTypeDecimalPad,     数字键盘 有数字和小数点
    UIKeyboardTypeTwitter,        优化的键盘，方便输入@、#字符
    UIKeyboardTypeAlphabet = UIKeyboardTypeASCIICapable,

} UIKeyboardType;