IOS控件行为、属性监测

让做个限制TextField输入长度的功能，本想着听简单的，直接去找对应的委托，在网上搜一下得到基本统一结论是使用下边的方法：

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {

    if ([string isEqualToString:@"\n"])

        returnYES;

    //限制最大输入字符长度为9

    NSString * toBeString = [textField.text stringByReplacingCharactersInRange:range withString:string];

    

    if (TRUE)

    {

        if ([toBeString length] >9) {

            textField.text = [toBeString substringToIndex:9];

            returnNO;

        }

    }

    returnYES;

}

没想到啊。。。。测试一直说没有限制输入长度，就自己试了几次，没有什么问题，一直到TMD发现了这个玩意：

这种情况，随便点没反应啊；

最后使用下边的方法成功了，大家可以看下：

         [textField addTarget:selfaction:@selector(textFieldDidChange:)forControlEvents:UIControlEventEditingChanged];

-------------

- (void)textFieldDidChange:(UITextField *)textField

{

    if (TRUE) {//这里应该判断下是哪个TextField

        if (textField.text.length >9) {

            textField.text = [textField.textsubstringToIndex:9];

        }

    }

}

其实在UIKit框架的UIControl.h文件里定义了很多控件时间的枚举，很好用的：

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

};