我目前正在编写一个针对 iOS 6.1 SDK 的应用程序。我知道 iOS 7 中的某些内容可能不需要解决我的问题，但为了学习，我还是会问。
该应用程序将包含一个表格视图和自定义表格视图单元格。我希望单元格 contentView 的唯一子视图是自定义视图，其中包含使用 Core Text 绘制的 NSAttributedString 。由于每个单元格的字符串会有所不同，因此字形定位需要取决于字形的数量（即较长的字符串在字形之间的可见空间较小）。字体大小和物理边界必须保持不变，只是字形位置不同。
我有以下代码，无论出于何种原因，它都没有达到我的预期。
这是 BMPTeamNameView 的 .h - 自定义视图（contentView 的子视图）
@interface BMPTeamNameView : UIView
-(id)initWithFrame:(CGRect)frame text:(NSString *)text textInset:(UIEdgeInsets)insets font:(UIFont *)font;
@property (nonatomic, copy) NSAttributedString *attributedString;
@property (nonatomic, copy) NSString *text;
@property (nonatomic, strong) UIFont *font;
@property (nonatomic, assign) UIEdgeInsets insets;
@end
新的指定初始化器现在将设置框架、用于属性字符串的文本、确定文本 rect 相对于 contentView rect 的 insets 以及要使用的字体。
最初在我的自定义 drawRect 中：我使用了 CTFramesetterRef，但是 CTFramesetterRef 将创建一个不可变的框架，它（可能？）限制了单个字形的布局。在这个实现中，我使用 CTTypesetterRef 来创建 CTLineRef。当您比较 CTLineDraw() 和 CTFrameDraw() 时，使用 CTFrame 会导致不同的绘图行为，但这是另一个问题。我的 drawRect: 如下：
- (void)drawRect:(CGRect)rect
{
CGContextRef context = UIGraphicsGetCurrentContext();
// Flips the coordinates so that drawing will be right side up
CGContextSetTextMatrix(context, CGAffineTransformIdentity);
CGContextTranslateCTM(context, 0, self.bounds.size.height);
CGContextScaleCTM(context, 1.0, -1.0);
// Path that will hold the textRect
CGMutablePathRef path = CGPathCreateMutable();
// rectForTextInsets: returns a rect based on the insets with respect to cell contentView
self.textRect = [self rectForTextWithInsets:self.insets];
// Path adding / sets color for drawing
CGPathAddRect(path, NULL, self.textRect);
CGContextSetFillColorWithColor(context, [UIColor redColor].CGColor);
CGContextAddPath(context, path);
CGContextFillPath(context);
// convenience method to return dictionary of attributes for string
NSDictionary *attributes = [self attributesForAttributedString];
// convenience method returns "Hello World" with attributes
// typesetter property is set in the custom setAttributedString:
self.attributedString = [self attributedStringWithAttributes:attributes];
CTTypesetterRef typesetter = self.typesetter;
// Creates the line for the attributed string
CTLineRef line = CTTypesetterCreateLine(typesetter, CFRangeMake(0, 0));
CGPoint *positions = NULL;
CGGlyph *glyphs = NULL;
CGPoint *positionsBuffer = NULL;
CGGlyph *glyphsBuffer = NULL;
// We will only have one glyph run
CFArrayRef glyphRuns = CTLineGetGlyphRuns(line);
CTRunRef glyphRun = CFArrayGetValueAtIndex(glyphRuns, 0);
// Get the count of all the glyphs
NSUInteger glyphCount = CTRunGetGlyphCount(glyphRun);
// This function gets the ptr to the glyphs, may return NULL
glyphs = (CGGlyph *)CTRunGetGlyphsPtr(glyphRun);
if (glyphs == NULL) {
// if glyphs is NULL allocate a buffer for them
// store them in the buffer
// set the glyphs ptr to the buffer
size_t glyphsBufferSize = sizeof(CGGlyph) * glyphCount;
CGGlyph *glyphsBuffer = malloc(glyphsBufferSize);
CTRunGetGlyphs(glyphRun, CFRangeMake(0, 0), glyphsBuffer);
glyphs = glyphsBuffer;
}
// This function gets the ptr to the positions, may return NULL
positions = (CGPoint *)CTRunGetPositionsPtr(glyphRun);
if (positions == NULL) {
// if positions is NULL allocate a buffer for them
// store them in the buffer
// set the positions ptr to the buffer
size_t positionsBufferSize = sizeof(CGPoint) * glyphCount;
CGPoint *positionsBuffer = malloc(positionsBufferSize);
CTRunGetPositions(glyphRun, CFRangeMake(0, 0), positionsBuffer);
positions = positionsBuffer;
}
// Changes each x by 15 and then sets new value at array index
for (int i = 0; i < glyphCount; i++) {
NSLog(@"positionAtIndex: %@", NSStringFromCGPoint(positions[i]));
CGPoint oldPosition = positions[i];
CGPoint newPosition = CGPointZero;
NSLog(@"oldPosition = %@", NSStringFromCGPoint(oldPosition));
newPosition.x = oldPosition.x + 15.0f;
newPosition.y = oldPosition.y;
NSLog(@"newPosition = %@", NSStringFromCGPoint(newPosition));
positions[i] = newPosition;
NSLog(@"positionAtIndex: %@", NSStringFromCGPoint(positions[i]));
}
// When CTLineDraw is commented out this will not display the glyphs on the screen
CGContextShowGlyphsAtPositions(context, glyphs, positions, glyphCount);
// When CGContextShowGlyphsAtPositions is commented out...
// This will draw the string however it aligns the text to the view's lower left corner
// CTFrameDraw would draw the text properly in the view's upper left corner
// This is the difference I was speaking of and I'm not sure why it is
CTLineDraw(line, context);
// Make sure to release any CF objects and release allocated buffers
CFRelease(path);
free(positionsBuffer);
free(glyphsBuffer);
}
我不确定为什么 CGContextShowGlyphsAtPositions() 没有正确显示字形或 CTLineDraw() 不会使用新的字形位置。我是否错误地处理了这些位置和字形的分配？穴居人调试显示字形与预期一致，并且位置正在更改。我知道我的代码并不能完全满足我正在寻找的内容（我将字形位置更改为 15.0f 而不是基于字符串）但是，我在布置这些字形时哪里出错了？