iOS實(shí)現(xiàn)一個(gè)意見反饋類型的輸入欄

@property (nonatomic, strong) UILabel *placholderLabel; //提示字符串 
@property (weak, nonatomic) IBOutlet UITextView *infoTF;
 
#define MAX_LIMIT_NUMS 120 //文本最大長度
 
- (void)controlView {
 self.infoTF.layer.borderWidth = 0.5;//邊寬
 self.infoTF.layer.cornerRadius = 5.0;//設(shè)置圓角
 self.infoTF.layer.borderColor =[UIColor grayColor].CGColor;
 self.infoTF.delegate = self;
 
 CGFloat width = self.infoTF.frame.size.width;
 
 self.placholderLabel = [[UILabel alloc] initWithFrame:CGRectMake(5, 0, width-5, 30)];
 self.placholderLabel.numberOfLines = 0;
 self.placholderLabel.text = setInternational(@"live.weibosummay.string");
 self.placholderLabel.textColor = setRGBColor(176, 176, 176);
 self.placholderLabel.font = ZKP15Font;
 [self.placholderLabel setHidden:NO];
 [self.infoTF addSubview:_placholderLabel];
}
 
//限制文本輸入長度
- (void)textViewDidChange:(UITextView*)textView{
 if([textView.text length] == 0){
  _placholderLabel.hidden = NO;
 }else{
  _placholderLabel.hidden = YES;//這里給空
 }
 
 UITextRange *selectedRange = [textView markedTextRange];
 //獲取高亮部分
 UITextPosition *pos = [textView positionFromPosition:selectedRange.start offset:0];
 //如果在變化中是高亮部分在變，就不要計(jì)算字符了
 if (selectedRange && pos) {
  return;
 }
 
 NSString *nsTextContent = textView.text;
 NSInteger existTextNum = nsTextContent.length;
 
 if (existTextNum > MAX_LIMIT_NUMS){
  //截取到最大位置的字符(由于超出截部分在should時(shí)被處理了所在這里這了提高效率不再判斷)
  NSString *s = [nsTextContent substringToIndex:MAX_LIMIT_NUMS];
  
  [textView setText:s];
 }
}
//設(shè)置超出最大字?jǐn)?shù)（120字）即不可輸入 也是textview的代理方法
- (BOOL)textView:(UITextView*)textView shouldChangeTextInRange:(NSRange)range
 replacementText:(NSString*)text{
 
 UITextRange *selectedRange = [textView markedTextRange];
 //獲取高亮部分
 UITextPosition *pos = [textView positionFromPosition:selectedRange.start offset:0];
 
 //如果有高亮且當(dāng)前字?jǐn)?shù)開始位置小于最大限制時(shí)允許輸入
 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 < MAX_LIMIT_NUMS) {
   return YES;
  }else{
   return NO;
  }
 }
 
 NSString *comcatstr = [textView.text stringByReplacingCharactersInRange:range withString:text];
 
 NSInteger caninputlen = MAX_LIMIT_NUMS - comcatstr.length;
 
 if (caninputlen >= 0){
  return YES;
 }else{
  NSInteger len = text.length + caninputlen;
  //防止當(dāng)text.length + caninputlen < 0時(shí)，使得rg.length為一個(gè)非法最大正數(shù)出錯(cuò)
  NSRange rg = {0,MAX(len,0)};
  
  if (rg.length > 0){
   NSString *s = @"";
   //判斷是否只普通的字符或asc碼(對(duì)于中文和表情返回NO)
   BOOL asc = [text canBeConvertedToEncoding:NSASCIIStringEncoding];
   if (asc) {
    s = [text substringWithRange:rg];//因?yàn)槭莂scii碼直接取就可以了不會(huì)錯(cuò)
   }else{
    __block NSInteger idx = 0;
    __block NSString *trimString = @"";//截取出的字串
    //使用字符串遍歷，這個(gè)方法能準(zhǔn)確知道每個(gè)emoji是占一個(gè)unicode還是兩個(gè)
    [text enumerateSubstringsInRange:NSMakeRange(0, [text length])
           options:NSStringEnumerationByComposedCharacterSequences
          usingBlock: ^(NSString* substring, NSRange substringRange, NSRange enclosingRange, BOOL* stop) {
           
           NSInteger steplen = substring.length;
           if (idx >= rg.length) {
            *stop = YES; //取出所需要就break，提高效率
            return ;
           }
           
           trimString = [trimString stringByAppendingString:substring];
           
           idx = idx + steplen;//這里變化了，使用了字串占的長度來作為步長 
          }];
    
    s = trimString;
   }
   //rang是指從當(dāng)前光標(biāo)處進(jìn)行替換處理(注意如果執(zhí)行此句后面返回的是YES會(huì)觸發(fā)didchange事件)
   [textView setText:[textView.text stringByReplacingCharactersInRange:range withString:s]];
  }
  return NO;
 }
}