iOS UITextField 限制输入长度，中英文混排，汉字占2个长度，英文数字占1个长度

#import <UIKit/UIKit.h>

@interface UITextField (HL_LimitLength)
/**
*  使用时只要调用此方法，加上一个长度(int)，就可以实现了字数限制,配合tools中的方法  可以支持汉字。汉字占2个长度
*
*  @param length
*/
- (void)limitTextLength:(int)length;
/**
*  uitextField 抖动效果
*/
- (void)shake;
@end

//
//  UITextField+HL_LimitLength.m
//  HitLive
//
//  Created by 王飞 on 16/4/8.
//  Copyright © 2016年 国广星空视频科技（北京）有限公司. All rights reserved.
//

#import "UITextField+HL_LimitLength.h"

@implementation UITextField (HL_LimitLength)
static NSString *kLimitTextLengthKey = @"kLimitTextLengthKey";
- (void)limitTextLength:(int)length
{
objc_setAssociatedObject(self, (__bridge const void *)(kLimitTextLengthKey), [NSNumber numberWithInt:length], OBJC_ASSOCIATION_RETAIN_NONATOMIC);

[self addTarget:self action:@selector(textFieldTextLengthLimit:) forControlEvents:UIControlEventEditingChanged];

}
- (void)textFieldTextLengthLimit:(id)sender
{
NSNumber *lengthNumber = objc_getAssociatedObject(self, (__bridge const void *)(kLimitTextLengthKey));
int length = [lengthNumber intValue];
//下面是修改部分
bool isChinese;//判断当前输入法是否是中文
NSArray *currentar = [UITextInputMode activeInputModes];
UITextInputMode *current = [currentar firstObject];
//[[UITextInputMode currentInputMode] primaryLanguage]，废弃的方法
if ([current.primaryLanguage isEqualToString: @"en-US"]) {
isChinese = false;
}
else
{
isChinese = true;
}

if(sender == self) {
// length是自己设置的位数
NSString *str = [[self text] stringByReplacingOccurrencesOfString:@"?" withString:@""];
if (isChinese) { //中文输入法下
//          int  chineseLength = length/2;
UITextRange *selectedRange = [self markedTextRange];
//获取高亮部分
UITextPosition *position = [self positionFromPosition:selectedRange.start offset:0];
// 没有高亮选择的字，则对已输入的文字进行字数统计和限制
if (!position) {
//                if ( str.length>=length) {
int textcount = [Tools convertToInt:[self text]];
if ([Tools convertToInt:[self text]] >= length) {
NSString *strNew = [NSString stringWithString:str];
int chineseCount = [[NSString stringWithFormat:@"%lu",textcount - str.length] intValue];

int indexCount = (length/2 -(textcount - 2*chineseCount)/2 )+ (textcount - 2*chineseCount);

[self setText:[strNew substringToIndex:indexCount]];
}
}
else
{
// NSLog(@"输入的");

}
}else{
if ([str length]>=length) {
NSString *strNew = [NSString stringWithString:str];
[self setText:[strNew substringToIndex:length]];
}
}
}
}

- (void)shake
{
CAKeyframeAnimation *keyAn = [CAKeyframeAnimation animationWithKeyPath:@"position"];
[keyAn setDuration:0.5f];
NSArray *array = [[NSArray alloc] initWithObjects:
[NSValue valueWithCGPoint:CGPointMake(self.center.x, self.center.y)],
[NSValue valueWithCGPoint:CGPointMake(self.center.x-5, self.center.y)],
[NSValue valueWithCGPoint:CGPointMake(self.center.x+5, self.center.y)],
[NSValue valueWithCGPoint:CGPointMake(self.center.x, self.center.y)],
[NSValue valueWithCGPoint:CGPointMake(self.center.x-5, self.center.y)],
[NSValue valueWithCGPoint:CGPointMake(self.center.x+5, self.center.y)],
[NSValue valueWithCGPoint:CGPointMake(self.center.x, self.center.y)],
[NSValue valueWithCGPoint:CGPointMake(self.center.x-5, self.center.y)],
[NSValue valueWithCGPoint:CGPointMake(self.center.x+5, self.center.y)],
[NSValue valueWithCGPoint:CGPointMake(self.center.x, self.center.y)],
nil];
[keyAn setValues:array];

NSArray *times = [[NSArray alloc] initWithObjects:
[NSNumber numberWithFloat:0.1f],
[NSNumber numberWithFloat:0.2f],
[NSNumber numberWithFloat:0.3f],
[NSNumber numberWithFloat:0.4f],
[NSNumber numberWithFloat:0.5f],
[NSNumber numberWithFloat:0.6f],
[NSNumber numberWithFloat:0.7f],
[NSNumber numberWithFloat:0.8f],
[NSNumber numberWithFloat:0.9f],
[NSNumber numberWithFloat:1.0f],
nil];
[keyAn setKeyTimes:times];

[self.layer addAnimation:keyAn forKey:@"TextAnim"];
}

@end

+(int)convertToInt:(NSString*)strtemp {

int strlength = 0;
char* p = (char*)[strtemp cStringUsingEncoding:NSUnicodeStringEncoding];
for (int i=0 ; i<[strtemp lengthOfBytesUsingEncoding:NSUnicodeStringEncoding] ;i++) {
if (*p) {
p++;
strlength++;
}
else {
p++;
}
}
return strlength;

}