gitDemo地址：https://github.com/laity1991/WKTextView
一.前言
- 之前做项目封装textView时存在一些bug一直未解决：文本信息在用户粘贴过长超出设定的最大字数时、带emoji时截取显示半个或乱码（因为emoji在iOS中使用的是UTF16也就是占位符是8+8两个字节的，占的长度为2,因此在计算字数时一个表情就占了2）
- 查了网上的一些封装demo，或是不太全或是存在一些小bug，在此我整理封装了一套WKTextView，方便大家使用和自己备用，主要解决问题：**
1.添加了占位文本 ，类似于textField的placeholder
2.中，英文字符输入时限制。
3.带emoji时截取显示半个或乱码字符处理。
4.处理了用户在粘贴过来文本超出字数限制存在bug的情况**- ** 这里用到了我写的UIView的一个分类UIView+WKCategory (重写frame setter、getter方法)，注释比较详细，不做过多赘述**
二 .WKTextView源码
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*** WKTextView.h ***
#import <UIKit/UIKit.h> @interface WKTextView : UITextView //文字 @property(nonatomic,copy) NSString *myPlaceholder; //文字颜色 @property(nonatomic,strong) UIColor *myPlaceholderColor; //最多输入字数 @property (nonatomic, assign) NSInteger maxNum; ///右下角统计字数label @property (nonatomic, strong) UILabel *countLabel; @end -
*** WKTextView.m ***
#import "WKTextView.h"
#import "UIView+WKCategory.h"
@interface WKTextView()<UITextViewDelegate>
@property (nonatomic,weak) UILabel *placeholderLabel;
@end@implementation WKTextView - (instancetype)initWithFrame:(CGRect)frame{ self = [super initWithFrame:frame]; if (self) { UILabel *placeholderLabel = [[UILabel alloc]init]; [self addSubview:placeholderLabel]; placeholderLabel.textColor = [UIColor lightGrayColor]; self.placeholderLabel= placeholderLabel; UILabel *countLabel = [[UILabel alloc]init]; [self addSubview:countLabel]; countLabel.frame = CGRectMake(self.width - 60, self.height - 40, 60, 40); countLabel.textAlignment = NSTextAlignmentCenter; countLabel.textColor = [UIColor lightGrayColor]; countLabel.text = @"0/100"; self.countLabel = countLabel; ///设置边框 self.layer.masksToBounds = YES; self.layer.cornerRadius = 4; self.layer.borderColor = [UIColor grayColor].CGColor; self.layer.borderWidth = 1; self.delegate = self; return self; } - (void)layoutSubviews{ [super layoutSubviews]; self.placeholderLabel.x = 8; self.placeholderLabel.y = 8; self.placeholderLabel.width = self.width - 2*self.placeholderLabel.x; ///根据占位文字myPlaceholder 算出占位Label的高度(宽度已定 高速自适应) CGSize maxSize = CGSizeMake(self.placeholderLabel.width, MAXFLOAT); self.placeholderLabel.height = [self.myPlaceholder boundingRectWithSize:maxSize options:NSStringDrawingUsesFontLeading | NSStringDrawingUsesLineFragmentOrigin attributes:@{NSFontAttributeName:self.placeholderLabel.font} context:nil].size.height; } ///箭头textView的输入文字变化 以此控制占位label的显示和隐藏 - (void)textDidChange{ //hasText是UITextView的属性 如果textView输入了文字就是 YES 没有文字就是NO self.placeholderLabel.hidden = self.hasText; } #pragma mark - UITextViewDelegate - (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text{ if ([text isEqualToString:@"\n"]) { [self resignFirstResponder]; return NO; } UITextRange *selectedRange = [textView markedTextRange]; //获取高亮部分 UITextPosition *pos = [textView positionFromPosition:selectedRange.start offset:0]; //获取高亮部分内容 //NSString * selectedtext = [textView textInRange:selectedRange]; //如果有高亮且当前字数开始位置小于最大限制时允许输入 if (selectedRange && pos) { NSInteger startOffset = [textView offsetFromPosition:textView.beginningOfDocument toPosition:selectedRange.start]; NSInteger endOffset = [textView offsetFromPosition:textView.beginningOfDocument toPosition:selectedRange.end]; NSRange offsetRange = NSMakeRange(startOffset, endOffset - startOffset); if (offsetRange.location < self.maxNum) { return YES; } else { return NO; } } NSString *comcatstr = [textView.text stringByReplacingCharactersInRange:range withString:text]; NSInteger caninputlen = self.maxNum - comcatstr.length; if (caninputlen >= 0) { return YES; } else { NSInteger len = text.length + caninputlen; //防止当text.length + caninputlen < 0时，使得rg.length为一个非法最大正数出错 NSRange rg = {0,MAX(len,0)}; if (rg.length > 0) { NSString *s = @""; //判断是否只普通的字符或asc码(对于中文和表情返回NO) BOOL asc = [text canBeConvertedToEncoding:NSASCIIStringEncoding]; if (asc) { s = [text substringWithRange:rg];//因为是ascii码直接取就可以了不会错 } else { __block NSInteger idx = 0; __block NSString *trimString = @"";//截取出的字串 //使用字符串遍历，这个方法能准确知道每个emoji是占一个unicode还是两个 [text enumerateSubstringsInRange:NSMakeRange(0, [text length]) options:NSStringEnumerationByComposedCharacterSequences usingBlock: ^(NSString* substring, NSRange substringRange, NSRange enclosingRange, BOOL* stop) { if (idx >= rg.length) { *stop = YES; //取出所需要就break，提高效率 return ; } trimString = [trimString stringByAppendingString:substring]; idx++; }]; s = trimString; } //rang是指从当前光标处进行替换处理(注意如果执行此句后面返回的是YES会触发didchange事件) [textView setText:[textView.text stringByReplacingCharactersInRange:range withString:s]]; //既然是超出部分截取了，哪一定是最大限制了。 self.countLabel.text = [NSString stringWithFormat:@"%ld/%ld",(long)self.maxNum,(long)self.maxNum]; } return NO; } } - (void)textViewDidChange:(UITextView *)textView{ self.placeholderLabel.hidden = self.hasText; UITextRange *selectedRange = [textView markedTextRange]; //获取高亮部分 UITextPosition *pos = [textView positionFromPosition:selectedRange.start offset:0]; //如果在变化中是高亮部分在变，就不要计算字符了 if (selectedRange && pos) { return; } NSString *nsTextContent = textView.text; NSInteger existTextNum = nsTextContent.length; if (existTextNum > self.maxNum) { //截取到最大位置的字符(由于超出截部分在should时被处理了所在这里这了提高效率不再判断) NSString *s = [nsTextContent substringToIndex:self.maxNum]; [textView setText:s]; } if (existTextNum > 100) { existTextNum = 100; } //不让显示负数 self.countLabel.text = [NSString stringWithFormat:@"%ld/%ld",MAX(0, existTextNum), (long)self.maxNum ]; } #pragma mark - setter - (void)setMaxNum:(NSInteger)maxNum{ _maxNum = maxNum; self.countLabel.text = [NSString stringWithFormat:@"0/%ld", (long)_maxNum]; } - (void)setMyPlaceholder:(NSString *)myPlaceholder{ _myPlaceholder = myPlaceholder; self.placeholderLabel.text = _myPlaceholder; ///重新计算占位label frame [self setNeedsLayout]; } - (void)setMyPlaceholderColor:(UIColor *)myPlaceholderColor{ _myPlaceholderColor = myPlaceholderColor; self.countLabel.textColor = myPlaceholderColor; self.placeholderLabel.textColor = _myPlaceholderColor; } ///从写TextView setFont方法 使占位labe、TextView、文字统计 Label Font一致 - (void)setFont:(UIFont *)font{ [super setFont:font]; self.placeholderLabel.font = font; self.countLabel.font = font; ///重新计算占位label frame [self setNeedsLayout]; } @end -
*** Demo ***
- (void)prepareForUI{ ///添加到父控件 WKTextView *textView = [[WKTextView alloc]initWithFrame:CGRectMake(50, 50, self.view.width - 100, 200)]; ///设置文本输入框的占位字符 textView.myPlaceholder = @"我是占位字符串..."; textView.font = [UIFont systemFontOfSize:14]; textView.maxNum = 100; [self.view addSubview:textView]; } 相关属性都暴露了出来，可以自行设置，效果如下：
WKTextView.gif
