IOS之监听UITextField的编辑事件

1、如果需要在UIViewController中监听UITextField的编辑事件，可以在视图控制器以下方法进行处理

@protocol UITextFieldDelegate 

@optional

- (BOOL)textFieldShouldBeginEditing:(UITextField *)textField;        // return NO to disallow editing.
- (void)textFieldDidBeginEditing:(UITextField *)textField;           // became first responder
- (BOOL)textFieldShouldEndEditing:(UITextField *)textField;          // return YES to allow editing to stop and to resign first responder status. NO to disallow the editing session to end
- (void)textFieldDidEndEditing:(UITextField *)textField;             // may be called if forced even if shouldEndEditing returns NO (e.g. view removed from window) or endEditing:YES called

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string;   // return NO to not change text

- (BOOL)textFieldShouldClear:(UITextField *)textField;               // called when clear button pressed. return NO to ignore (no notifications)
- (BOOL)textFieldShouldReturn:(UITextField *)textField;              // called when 'return' key pressed. return NO to ignore.

@end

2、如果某个类继承UITextField，需要在该类内部实现监听，可以按以下方法处理

- (id)initWithFrame:(CGRect)frame {
    self = [super initWithFrame:frame];
    if (self)
    {
        [self addTarget:self action:@selector(onChange:) forControlEvents:UIControlEventEditingDidEnd];// 可在自定义selector处理
    }
    return self;
}



typedef NS_OPTIONS(NSUInteger, UIControlEvents) {
    UIControlEventTouchDown           = 1 <<  0,      // on all touch downs
    UIControlEventTouchDownRepeat     = 1 <<  1,      // on multiple touchdowns (tap count > 1)
    UIControlEventTouchDragInside     = 1 <<  2,
    UIControlEventTouchDragOutside    = 1 <<  3,
    UIControlEventTouchDragEnter      = 1 <<  4,
    UIControlEventTouchDragExit       = 1 <<  5,
    UIControlEventTouchUpInside       = 1 <<  6,
    UIControlEventTouchUpOutside      = 1 <<  7,
    UIControlEventTouchCancel         = 1 <<  8,

    UIControlEventValueChanged        = 1 << 12,     // sliders, etc.

    UIControlEventEditingDidBegin     = 1 << 16,     // UITextField
    UIControlEventEditingChanged      = 1 << 17,
    UIControlEventEditingDidEnd       = 1 << 18,
    UIControlEventEditingDidEndOnExit = 1 << 19,     // 'return key' ending editing

    UIControlEventAllTouchEvents      = 0x00000FFF,  // for touch events
    UIControlEventAllEditingEvents    = 0x000F0000,  // for UITextField
    UIControlEventApplicationReserved = 0x0F000000,  // range available for application use
    UIControlEventSystemReserved      = 0xF0000000,  // range reserved for internal framework use
    UIControlEventAllEvents           = 0xFFFFFFFF
};