前言：項目中遇見的一個小需求，覺著挺有意思的榛鼎，這里記錄一下乞封。

1.需求：想要實(shí)現(xiàn)的效果如圖所示，即在TextField中居中展示一個搜索圖標(biāo)+一段默認(rèn)文字蜈首。

2.實(shí)現(xiàn)思路：當(dāng)然實(shí)現(xiàn)的思路有多種嗅蔬，這里我主要是利用UITextField的屬性attributedPlaceholder，實(shí)現(xiàn)一個圖文混排的NSMutableAttributedString.

效果圖.png

3.實(shí)現(xiàn)中遇到的問題：

a.圖文混排內(nèi)容在Textfield中居中的問題

問題a.png

b.圖文混排的圖片與文字不對齊的問題

問題b.png

廢話不多說疾就，直接上我主要實(shí)現(xiàn)代碼:

    self.view.backgroundColor = [UIColor lightGrayColor];
    
    self.searchTextfield = [[UITextField alloc]initWithFrame:CGRectMake(20, 40, [[UIScreen mainScreen] bounds].size.width-40, 40)];
    self.searchTextfield.backgroundColor = [UIColor whiteColor];
    self.searchTextfield.borderStyle = UITextBorderStyleRoundedRect;
    NSString *textString = @"請輸入用戶手機(jī)號搜索";
    NSMutableAttributedString *attributeString = [[NSMutableAttributedString alloc]initWithString:textString];
    // 插入圖片附件
    NSTextAttachment *imageAtta = [[NSTextAttachment alloc] init];
    imageAtta.bounds = CGRectMake(0, 0, 21, 21);
    imageAtta.image = [UIImage imageNamed:@"f_search"];
    NSAttributedString *attach = [NSAttributedString attributedStringWithAttachment:imageAtta];
    [attributeString insertAttributedString:attach atIndex:0];
    
    // 段落樣式
    NSMutableParagraphStyle *style = [[NSMutableParagraphStyle alloc]init];
    ///計算placeHolder文字寬度
    CGSize textSize = [textString boundingRectWithSize:CGSizeMake(CGFLOAT_MAX, CGFLOAT_MAX) options:NSStringDrawingUsesLineFragmentOrigin|NSStringDrawingUsesFontLeading attributes:@{NSFontAttributeName:[UIFont systemFontOfSize:16]} context:nil].size;
    
    // 縮進(jìn)以實(shí)現(xiàn)居中展示(解決問題a)
    [style setFirstLineHeadIndent:([[UIScreen mainScreen] bounds].size.width-40-21-textSize.width)/2.0];
    [attributeString addAttribute:NSParagraphStyleAttributeName value:style range:NSMakeRange(0, attributeString.length)];
    
    [attributeString addAttribute:NSFontAttributeName value:[UIFont systemFontOfSize:16] range:NSMakeRange(1, attributeString.length - 1)];
    ///解決問題b
    [attributeString addAttribute:NSBaselineOffsetAttributeName value:@(0.36 * 16) range:NSMakeRange(1, attributeString.length - 1)];
    self.searchTextfield.attributedPlaceholder = attributeString;
    [self.view addSubview:self.searchTextfield];

問題b解決借鑒自 解決使用NSMutableAttributedString 設(shè)置不同字體澜术，文字不能居中對齊
最終實(shí)現(xiàn)效果:

finalResult.gif