UITextField限制输入中文字数

前面写一了篇，UITextField Category来限制输入的字数，是有个Bug的，要输入中文时会crash。如今改动 了下。代码例如以下

.h文件

#import <UIKit/UIKit.h>

@interface UITextField (LimitLength)
/**
 *  使用时仅仅要调用此方法，加上一个长度(int)。就能够实现了字数限制,汉字不能够
 *
 *  @param length
 */
- (void)limitTextLength:(int)length;
/**
 *  uitextField 抖动效果
 */
- (void)shake;
@end

.m文件

#import "UITextField+LimitLength.h"
#import <objc/runtime.h>

@implementation UITextField (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];
    //以下是改动部分
    bool isChinese;//推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
            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) {
                    NSString *strNew = [NSString stringWithString:str];
                    [self setText:[strNew substringToIndex:length]];
                }
            }
            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

參考：http://www.keepwhy.com/index.php/archives/296

http://blog.sina.com.cn/s/blog_60f977e70101g4gj.html

http://www.2cto.com/kf/201406/312073.html