iOS 做个意见反馈类型的输入栏

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要做个意见反馈,TextField只有一行,TextView没有提示,好尬,只有做一个了,就是使用TextView作为输入框,添加个label作为提示,这里的关键是输入内容的限制,我这里限制了120字,但是要考虑很多方面的东西,来看代码

@property (nonatomic, strong) UILabel *placholderLabel; //提示字符串 
@property (weak, nonatomic) IBOutlet UITextView *infoTF;

#define MAX_LIMIT_NUMS 120  //文本最大长度

- (void)controlView {
    self.infoTF.layer.borderWidth = 0.5;//边宽
    self.infoTF.layer.cornerRadius = 5.0;//设置圆角
    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];
}

//限制文本输入长度
- (void)textViewDidChange:(UITextView*)textView{
    if([textView.text length] == 0){
        _placholderLabel.hidden = NO;
    }else{
        _placholderLabel.hidden = YES;//这里给空
    }

    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 > MAX_LIMIT_NUMS){
        //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:MAX_LIMIT_NUMS];
        
        [textView setText:s];
    }
}
//设置超出最大字数(120字)即不可输入 也是textview的代理方法
- (BOOL)textView:(UITextView*)textView shouldChangeTextInRange:(NSRange)range
 replacementText:(NSString*)text{

    UITextRange *selectedRange = [textView markedTextRange];
    //获取高亮部分
    UITextPosition *pos = [textView positionFromPosition:selectedRange.start offset:0];

    //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 < 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) {
                                          
                                          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;//这里变化了,使用了字串占的长度来作为步长  
                                      }];
                
                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]];
        }
        return NO;
    }
}

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