如何将制表位添加到NSAttributedString并在UITextView中显示

我正在创建一个iOS应用程序,我想显示一个属性字符串 UITextView中指定的特定制表位。我也想画它们 使用drawRect中的核心文本直接进入UIViews。我想要(如果可能的话) 以便在两种情况下使用相同的属性字符串。

因此,在我的应用程序中,我创建了一个CFAttributedStringRef或NSAttributedString 对其应用CTParagraphStyle属性。然后,我尝试显示 UITextView中的属性字符串,我会出现如下崩溃:

-[__NSCFType headIndent]: unrecognized selector sent to instance 0x7545080

po 0x7545080
$0 = 122966144 CTParagraphStyle:
base writing direction = -1, alignment = 4, line break mode = 0, 
   default tab interval = 0
first line head indent = 0, head indent = 0, tail indent = 0
line height multiple = 0, maximum line height = 0, minimum line height = 0
line spacing adjustment = 0, paragraph spacing = 0, 
   paragraph spacing before = 0
tabs:
(
   "CTTextTab: location = 20, alignment = 0, options = (none)\n",
   "CTTextTab: location = 40, alignment = 0, options = (none)\n",
   "CTTextTab: location = 60, alignment = 0, options = (none)\n",
   "CTTextTab: location = 80, alignment = 0, options = (none)\n",
   "CTTextTab: location = 100, alignment = 0, options = (none)\n",
   "CTTextTab: location = 120, alignment = 0, options = (none)\n"
)

我知道发生了什么,但我想知道我是否有其他办法 做我想做的事。iOS上的NSMutableParagraphStyle没有选项卡 停止支持,但我注意到OSX上的NSMutableParagraphStyle确实有这个 能力。这让我想到iOS NSMutableParagraphStyle可能 总有一天会支持这一点。

同时,有没有办法将制表位添加到CFAttributedStringRef或 NSAttributedString,并且仍然有UITextView显示它?

有问题的来源是:

- (void)viewWillAppear:(BOOL)animated
{
   CFDictionaryRef attrs = (__bridge CFDictionaryRef) @{};
   CFAttributedStringRef a = CFAttributedStringCreate(
       kCFAllocatorDefault, CFSTR("a\tb\tc\td"), attrs);

   CFMutableAttributedStringRef attrStr;
   attrStr = CFAttributedStringCreateMutableCopy(
       kCFAllocatorDefault, CFAttributedStringGetLength(a), a);

   CFArrayRef tabStops = (__bridge CFArrayRef) @[
       (__bridge id) CTTextTabCreate(0, 20, NULL),
       (__bridge id) CTTextTabCreate(0, 40, NULL),
       (__bridge id) CTTextTabCreate(0, 60, NULL),
       (__bridge id) CTTextTabCreate(0, 80, NULL),
       (__bridge id) CTTextTabCreate(0, 100, NULL),
       (__bridge id) CTTextTabCreate(0, 120, NULL)];

   const CTParagraphStyleSetting paraSettings[] = {
       {kCTParagraphStyleSpecifierTabStops, sizeof(CFArrayRef), &tabStops},
   };

   CTParagraphStyleRef paraStyle = CTParagraphStyleCreate(
       paraSettings, 
       sizeof(paraSettings) / sizeof(CTParagraphStyleSetting));

   CFRange range = CFRangeMake(0, CFAttributedStringGetLength(attrStr));
   CFAttributedStringSetAttribute(
       attrStr, range, kCTParagraphStyleAttributeName, paraStyle);

   CFRelease(paraStyle);
   CFIndex i, count = CFArrayGetCount(tabStops);
   for (i = 0; i < count; i++) {
       CFRelease(CFArrayGetValueAtIndex(tabStops, i));
   }

   [[self textView] setAttributedText:
       (__bridge NSAttributedString *)(attrStr)];
}