你真的了解UITextField吗？

一：首先查看一下关于UITextField的定义

NS_CLASS_AVAILABLE_IOS(2_0) @interface UITextField : UIControl <UITextInput, NSCoding> 

@property(nullable, nonatomic,copy)   NSString               *text;        //值         
@property(nullable, nonatomic,copy)   NSAttributedString     *attributedText NS_AVAILABLE_IOS(6_0);  //富文本的值
@property(nullable, nonatomic,strong) UIColor                *textColor;            // 文字色
@property(nullable, nonatomic,strong) UIFont                 *font;                 // 字体
@property(nonatomic)        NSTextAlignment         textAlignment;        // 默认值 NSLeftTextAlignment 排版
@property(nonatomic)        UITextBorderStyle       borderStyle;          // 默认值 UITextBorderStyleNone 边框的样式
@property(nonatomic,copy)   NSDictionary<NSString *, id>           *defaultTextAttributes NS_AVAILABLE_IOS(7_0); // 文本属性 用字典填充

@property(nullable, nonatomic,copy)   NSString               *placeholder;          // 空值时的提示文字
@property(nullable, nonatomic,copy)   NSAttributedString     *attributedPlaceholder NS_AVAILABLE_IOS(6_0); // 富文本的空值提示文字
@property(nonatomic)        BOOL                    clearsOnBeginEditing; // 默认值 NO 如果设为YES 再次编辑就清空
@property(nonatomic)        BOOL                    adjustsFontSizeToFitWidth; // 默认值NO，若设为YES 当文字超出文本框宽度时，自动调整文字大小
@property(nonatomic)        CGFloat                 minimumFontSize;      // 默认值 0.0.最小可缩小的字号和adjustsFontSizeToFitWidth一起使用
@property(nullable, nonatomic,weak)   id<UITextFieldDelegate> delegate;         //代理    
@property(nullable, nonatomic,strong) UIImage                *background;           //设置背景 注意只有UITextBorderStyleNone的时候改属性有效
@property(nullable, nonatomic,strong) UIImage                *disabledBackground;   //禁用的背景

@property(nonatomic,readonly,getter=isEditing) BOOL editing;  //是否被编辑
@property(nonatomic) BOOL allowsEditingTextAttributes NS_AVAILABLE_IOS(6_0); // 默认值 NO
@property(nullable, nonatomic,copy) NSDictionary<NSString *, id> *typingAttributes NS_AVAILABLE_IOS(6_0); 


@property(nonatomic)        UITextFieldViewMode  clearButtonMode; // 输入框中是否有个叉号 设置清除 何时显示

@property(nullable, nonatomic,strong) UIView              *leftView;        //  左边视图
@property(nonatomic)        UITextFieldViewMode  leftViewMode;    // 在什么状态下显示 默认值 UITextFieldViewModeNever

@property(nullable, nonatomic,strong) UIView              *rightView;       // 右边视图
@property(nonatomic)        UITextFieldViewMode  rightViewMode;   // 默认值 UITextFieldViewModeNever

//界面重写绘制行为
////重写来重置边缘区域
- (CGRect)borderRectForBounds:(CGRect)bounds;
//重写来重置文字区域
- (CGRect)textRectForBounds:(CGRect)bounds;
//重写来重置占位符区域
- (CGRect)placeholderRectForBounds:(CGRect)bounds;
//重写来重置编辑区域
- (CGRect)editingRectForBounds:(CGRect)bounds;
//重写来重置clearButton位置,改变size可能导致button的图片失真
- (CGRect)clearButtonRectForBounds:(CGRect)bounds;
- (CGRect)leftViewRectForBounds:(CGRect)bounds;
- (CGRect)rightViewRectForBounds:(CGRect)bounds;

//改变绘文字属性.重写时调用super可以按默认图形属性绘制,若自己完全重写绘制函数，就不用调用super了.
- (void)drawTextInRect:(CGRect)rect;
//重写改变绘制占位符属性.重写时调用super可以按默认图形属性绘制,若自己完全重写绘制函数，就不用调用super了.
- (void)drawPlaceholderInRect:(CGRect)rect;

@property (nullable, readwrite, strong) UIView *inputView;     //代替标准的系统键盘        
@property (nullable, readwrite, strong) UIView *inputAccessoryView;  //编辑时显示在系统键盘或用户自定义的inputView上面的视图

@property(nonatomic) BOOL clearsOnInsertion NS_AVAILABLE_IOS(6_0); // 默认值NO
@end

UITextField是继承于UIControl，并且遵循NSCoding及UITextInput的协议；UITextInput的协议作用是用来辅助键盘输入得协议，在需要用到键盘输入得地方都需要实现这个协议；

知识点1：UITextBorderStyle的枚举内容

typedef NS_ENUM(NSInteger, UITextBorderStyle) {
    UITextBorderStyleNone,/无任何边框
    UITextBorderStyleLine,//黑色线框
    UITextBorderStyleBezel,//边线+阴影
    UITextBorderStyleRoundedRect //浅色带圆弧线框
};

知识点2：UITextFieldViewMode的枚举内容

typedef NS_ENUM(NSInteger, UITextFieldViewMode) {
    UITextFieldViewModeNever,//无清除按钮
    UITextFieldViewModeWhileEditing,//编辑时出现清除按钮
    UITextFieldViewModeUnlessEditing,//编辑时不出现，编辑后才出现清除按钮
    UITextFieldViewModeAlways //一直显示清除按钮
};

知识点3：关于NSTextAlignment的说明，UITextAlignmentLeft （水平右对齐），UITextAlignmentCenter（水平居中对齐），UITextAlignmentRight （水平右对齐）；

知识点4：修改UITextField中关于Placeholder的着色

[self.myTextField setValue:[UIColor grayColor] forKeyPath:@"_placeholderLabel.textColor"];

当然也可以采用另外一种方式：

 NSMutableAttributedString *attrString = [[NSMutableAttributedString alloc]initWithString:@"水印提示文字"];
  [attrString addAttribute:NSForegroundColorAttributeNam
                     value:[UIColor redColor]
                     range:NSMakeRange(0, 2)];
  myTextFieldattributedPlaceholder =  attrString;

知识点5：关于leftView跟leftViewMode的运用

            _relayTextField = [[UITextField alloc] initWithFrame:CGRectMake(0, 0, 0, 0)];
            _relayTextField.backgroundColor = [UIColor whiteColor];
            _relayTextField.font = [UIFont fontWithName:@"OpenSans" size:15.0];
            _relayTextField.delegate = self;
            _relayTextField.layer.cornerRadius = 5.0f;
            _relayTextField.layer.masksToBounds = YES;
            _relayTextField.clearButtonMode = UITextFieldViewModeWhileEditing;
            _relayTextField.autocorrectionType = UITextAutocorrectionTypeNo;
            _relayTextField.autocapitalizationType = UITextAutocapitalizationTypeNone;
            _relayTextField.returnKeyType=UIReturnKeySend;
            UILabel *label = [[UILabel alloc]initWithFrame:CGRectMake(0, 10, 70, 37)];
            label.font = [UIFont boldSystemFontOfSize:15];
            label.adjustsFontSizeToFitWidth = YES;
            label.textColor = COLOR_WORD_GRAY_2;
            _relayTextField.leftView = label;
            _relayTextField.leftViewMode = UITextFieldViewModeAlways;
            [self addSubview:_relayTextField];

设置显示的值：

-(void)configuerWithName:(NSString*)name messageId:(NSString*)message_id
{
    _name = name;
    _messageId = message_id;
    if ([_relayTextField.leftView isKindOfClass:[UILabel class]]) {
        ((UILabel*)_relayTextField.leftView).text = [NSString stringWithFormat:@"回复%@ :",name];
        ((UILabel*)_relayTextField.leftView).textColor = COLOR_WORD_GRAY_2;
    }
}

知识点6：inputView跟inputAccessoryView 默认是系统的键盘，比如有自定义的键盘就可以把它赋值给inputView;当然也可以是其它效果的视图，比如弹出选择器等；实例如下：

//自定义键盘，将原有的键盘隐藏，显示当前自定义视图
UIView *keyBoardContent = [[UIView alloc]initWithFrame:CGRectMake(0, 0, [UIScreen mainScreen].bounds.size.width, 100)];
keyBoardContent.backgroundColor = [UIColor darkGrayColor];
myTextField.inputView = keyBoardContent;


UIView *subView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, self.view.bounds.size.width, 80)];
subView.backgroundColor = [UIColor greenColor];
myTextField.inputAccessoryView = subView;

二：UITextInputTraits的相关内容，UITextField遵循这个协议，用来辅助键盘输入得协议，在需要用到键盘输入得地方都需要实现这个协议

@protocol UITextInputTraits <NSObject>

@optional

@property(nonatomic) UITextAutocapitalizationType autocapitalizationType; // default is UITextAutocapitalizationTypeSentences
@property(nonatomic) UITextAutocorrectionType autocorrectionType;         //是否纠错 默认值 UITextAutocorrectionTypeDefault
@property(nonatomic) UITextSpellCheckingType spellCheckingType NS_AVAILABLE_IOS(5_0); // default is UITextSpellCheckingTypeDefault;
@property(nonatomic) UIKeyboardType keyboardType;                         // 键盘类型 默认值UIKeyboardTypeDefault
@property(nonatomic) UIKeyboardAppearance keyboardAppearance;             // 设定键盘显示风格 默认值 UIKeyboardAppearanceDefault
@property(nonatomic) UIReturnKeyType returnKeyType;                       // default is UIReturnKeyDefault (See note under UIReturnKeyType enum)
@property(nonatomic) BOOL enablesReturnKeyAutomatically;                  // 设定当文本框没有输入内容时键盘得返回键是否可用@property(nonatomic,getter=isSecureTextEntry) BOOL secureTextEntry;       // 设定输入文本是否要受到隐藏保护，默认为NO不保护，设定为YES，则文本输入后为密码风格得保护

@end

知识点7：secureTextEntry是设置是否显示成密码的形式，此属性并不在UITextField里面

知识点8：UIReturnKeyType（UITextInputTraits中）的枚举内容如下

    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，用语搜索
    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
    UIReturnKeyYahoo        ;//标有Yahoo的蓝色按钮
    UIReturnKeyEmergencyCall;//紧急呼叫按钮

知识点9：autocapitalizationType（UITextInputTraits中）首字母是否大写

    UITextAutocapitalizationTypeNone         ;//不自动大写
    UITextAutocapitalizationTypeWords        ;//单词首字母大写
    UITextAutocapitalizationTypeSentences    ;//句子的首字母大写
    UITextAutocapitalizationTypeAllCharacters;//所有字母都大写

知识点10：keyboardAppearance（UITextInputTraits中）键盘外观

   UIKeyboardAppearanceDefault ;//默认外观，浅灰色
   UIKeyboardAppearanceAlert   ;//深灰石墨色

知识点11：autocorrectionType（UITextInputTraits中）是否纠错

    UITextAutocorrectionTypeDefault ;   //默认
    UITextAutocorrectionTypeNo      ;   //不自动纠错
    UITextAutocorrectionTypeYes     ;   //自动纠错

知识点12：使文本框在界面打开时就获取焦点，并弹出输入键盘：[myTextField becomeFirstResponder]; 使文本框失去焦点，并收回键盘[myTextFieldresignfirstresponder]

键盘收起其它方式
//方式 1:
[[[UIApplication sharedApplication]keyWindow] endEditing:YES];
//方式 2:
[[UIApplication sharedApplication]sendAction:@selector(resignFirstResponder) to:nil from:nil forEvent:nil];
//方式 3:
[self.view endEditing:YES];

知识点13：因为UITextFiled是继承于UIControl,所以它也是有增加事件addTaget的效果

[myTextField addTarget:self
          action:@selector(textFieldDidChange:)//私有方法
forControlEvents:UIControlEventEditingChanged];


- (void)textFieldDidChange:(UITextField*)textField{//类似UIButton addTag..监听方法
    NSLog(@"输入框内容 = %@",textField.text);
}

知识点14：关于UITextFiled的NotificaitonCenter监听

      UITextFieldTextDidBeginEditingNotification  ;//监听开始编辑
      UITextFieldTextDidChangeNotification        ;//监听正在编辑
      UITextFieldTextDidEndEditingNotification    ;//监听结束编辑

实例：
NSNotificationCenter *center = [NSNotificationCenter defaultCenter];
        [center addObserver:self
                   selector:@selector(texfFieldNotification:)
                       name:UITextFieldTextDidChangeNotification object:nil];

- (void)texfFieldNotification:(NSNotification*)noti{//私有方法
    NSLog(@"输入款变化了");
}

当然记得在用后时移除通知；

知识点15：监听键盘出现,知晓键盘CGRect

- (void)efObserverKeyBoardShowAndHidde{
    //注册键盘出现
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(keyBoardWasShow:)
                                                 name:UIKeyboardWillShowNotification
                                               object:nil];
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(keyBoardWillBeHidden:)
                                                 name:UIKeyboardWillHideNotification
                                               object:nil];
}
- (void)keyBoardWasShow:(NSNotification*)aNotification{
    NSLog(@"键盘出现");
    //键盘高度
    //CGRect keyBoardFrame = [[[aNotification userInfo] objectForKey:UIKeyboardFrameEndUserInfoKey] CGRectValue];
}
-(void)keyBoardWillBeHidden:(NSNotification*)aNotification{
    NSLog(@"键盘消失");
}

- (void)removeObserver{//移除所有通知
    [[NSNotificationCenter defaultCenter]removeObserver:self];
}

三：UITextField定义的协议UITextFieldDelegate内容

@protocol UITextFieldDelegate <NSObject>

@optional

- (BOOL)textFieldShouldBeginEditing:(UITextField *)textField;        // 返回一个BOOL值，指定是否循序文本字段开始编辑
- (void)textFieldDidBeginEditing:(UITextField *)textField;           // 开始编辑时触发，获得焦点时
- (BOOL)textFieldShouldEndEditing:(UITextField *)textField;          // 返回BOOL值，指定是否允许文本字段结束编辑，当编辑结束后
- (void)textFieldDidEndEditing:(UITextField *)textField;             // 结束编辑

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string;   // 用户不段的输入，可以控制达到某些条件，禁止输入

- (BOOL)textFieldShouldClear:(UITextField *)textField;               // 返回一个BOOL值指明是否满足什么条件清除内容
- (BOOL)textFieldShouldReturn:(UITextField *)textField;              // 返回一个BOOL值，指明是否允许在按下回车键时结束编辑

@end

知识点1：运用实例

//限定输入条件
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{
    //得到输入框的内容
    NSString * textString = [textField.text stringByReplacingCharactersInRange:range withString:string];

    if ([string isEqualToString:@"
"]) {
        NSLog(@"回车");
    }
    if ([string isEqualToString:@""]) {
        NSLog(@"后退");
    }
    if ([string isEqualToString:@" "]) {
        NSLog(@"空格");
        //return NO;//禁止空格输入
    }
    if (textString.length>4) {
        NSLog(@"输入超过5位数");
    }
    //打印当前键盘输入模式,en-US,zh-Hans....
    NSString *lang = [[UITextInputMode currentInputMode]primaryLanguage];

    //ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789
    //限制输入已知的字符
    NSCharacterSet *cs = [[NSCharacterSet characterSetWithCharactersInString:@"0123456789
"]invertedSet];
    //按cs分离出数组,数组按@""分离出字符串
    NSString *filtered = [[string componentsSeparatedByCharactersInSet:cs]componentsJoinedByString:@""]; 
    BOOL canChange = [string isEqualToString:filtered];

    return YES;
}


- (BOOL)textFieldShouldReturn:(UITextField *)textField{//辞去职务
    //主要是[receiver resignFirstResponder]在哪调用就能把receiver对应的键盘往下收
    [textField resignFirstResponder];
    return YES;
}