一、键盘风格
UIKit框架支持8种风格键盘
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+*#等符号
UIKeyboardTypeURL, // URL键盘，有.com按钮；只支持URL字符
UIKeyboardTypeNumberPad, //数字键盘
UIKeyboardTypePhonePad, // 电话键盘
UIKeyboardTypeNamePhonePad, // 电话键盘，也支持输入人名字
UIKeyboardTypeEmailAddress, // 用于输入电子邮件地址的键盘
} UIKeyboardType;
用法用例：
textView.keyboardtype = UIKeyboardTypeNumberPad;
二、键盘外观
typedef enum{
UIKeyboardAppearanceDefault, // 默认外观：浅灰色
UIKeyboardAppearanceDark // 黑色
UIKeyboardAppearanceLight // 白色
UIKeyboardAppearanceAlert = UIKeyboardAppearanceDark, // 深灰/石墨色/黑色
} UIKeyboardAppearance;
用法用例：
textView.keyboardAppearance = UIKeyboardAppearanceDefault;
三、回车键样式
typedef enum{
UIReturnKeyDefault, //默认：灰色按钮，标有Return
UIReturnKeyGo, //标有Go的蓝色按钮
UIReturnKeyGoogle, //标有Google的蓝色按钮，用于搜索
UIReturnKeyJoin, //标有Join的蓝色按钮
UIReturnKeyNext, //标有Next的蓝色按钮
UIReturnKeyRoute, //标有Route的蓝色按钮
UIReturnKeySearch, //标有Search的蓝色按钮
UIReturnKeySend, //标有Send的蓝色按钮
UIReturnKeyYahoo, //标有Yahoo!的蓝色按钮，用于搜索
UIReturnKeyDone, //标有Done的蓝色按钮
UIReturnKeyEmergencyCall, //紧急呼叫按钮
} UIReturnKeyType;
用法用例：
textView.returnKeyType = UIReturnKeyGo;
四、自动大写
typedef enum{
UITextAutocapitalizationTypeNone, //不自动大写
UITextAutocapitalizationTypeWords, //单词首字母大写
UITextAutocapitalizationTypeSentences, //句子首字母大写
UITextAutocapitalizationTypeAllCharacters, //所有字母大写
} UITextAutocapitalizationType;
用法用例：
textField.autocapitalizationType = UITextAutocapitalizationTypeWords;
五、自动更正
typedef enum {
UITextAutocorrectionTypeDefault, //默认
UITextAutocorrectionTypeNo, //不自动更正
UITextAutocorrectionTypeYes, //自动更正
} UITextAutocorrectionType;
用法用例：
textField.autocorrectionType = UITextAutocorrectionTypeYes;
六、安全文本输入
textView.secureTextEntry = YES;
