使用核心文本动态更改视图高度
我有一个观点,我想用Text Core(在iPad上)绘制文本。 当文字长大了,我想增加视图的高度,但我不知道如何计算框架所需的高度。 我用它在drawRect方法中绘制文本:
CGContextSetTextMatrix(context, CGAffineTransformIdentity);
CGContextTranslateCTM(context, 0, self.bounds.size.height);
CGContextScaleCTM(context, 1.0, -1.0);
CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef)currentTexts);
CGMutablePathRef textPath = CGPathCreateMutable();
CGRect textRect = CGRectMake(PADDING, PADDING, self.frame.size.width - 2 * PADDING, self.frame.size.height - 2 * PADDING);
CGPathAddRect(textPath, NULL, textRect);
CTFrameRef textFrame = CTFramesetterCreateFrame(framesetter, CFRangeMake(0, 0), textPath, NULL);
CTFrameDraw(textFrame, context);
CFRelease(textFrame);
CGPathRelease(textPath);
CFRelease(framesetter);
我试图使用sizeWithFont来获得文本的高度,并且:
- (CGSize) measureFrame: (CTFrameRef) frame
{
CGPathRef framePath = CTFrameGetPath(frame);
CGRect frameRect = CGPathGetBoundingBox(framePath);
CFArrayRef lines = CTFrameGetLines(frame);
CFIndex numLines = CFArrayGetCount(lines);
CGFloat maxWidth = 0;
CGFloat textHeight = 0;
// Now run through each line determining the maximum width of all the lines.
// We special case the last line of text. While we've got it's descent handy,
// we'll use it to calculate the typographic height of the text as well.
CFIndex lastLineIndex = numLines - 1;
for(CFIndex index = 0; index < numLines; index++)
{
CGFloat ascent, descent, leading, width;
CTLineRef line = (CTLineRef) CFArrayGetValueAtIndex(lines, index);
width = CTLineGetTypographicBounds(line, &ascent, &descent, &leading);
if(width > maxWidth)
{
maxWidth = width;
}
if(index == lastLineIndex)
{
// Get the origin of the last line. We add the descent to this
// (below) to get the bottom edge of the last line of text.
CGPoint lastLineOrigin;
CTFrameGetLineOrigins(frame, CFRangeMake(lastLineIndex, 1), &lastLineOrigin);
// The height needed to draw the text is from the bottom of the last line
// to the top of the frame.
textHeight = CGRectGetMaxY(frameRect) - lastLineOrigin.y + descent;
}
}
// For some text the exact typographic bounds is a fraction of a point too
// small to fit the text when it is put into a context. We go ahead and round
// the returned drawing area up to the nearest point. This takes care of the
// discrepencies.
return CGSizeMake(ceil(maxWidth), ceil(textHeight));
}
我用它来创建一个attrubuted字符串:
CTParagraphStyleSetting setting[1] = {
{kCTParagraphStyleSpecifierMinimumLineSpacing, sizeof(CGFloat), &minimumLineSpacing}
};
CTParagraphStyleRef paragraphStyle = CTParagraphStyleCreate(setting, 1);
NSDictionary *attr = [NSDictionary dictionaryWithObjectsAndKeys:
(id)textColor.CGColor, kCTForegroundColorAttributeName,
(id)currentFont, kCTFontAttributeName,
(id)paragraphStyle, kCTParagraphStyleAttributeName,
nil];
当我使用sizeWithFont时,在开始时一切正常,但是当文本有更多的线条时,框架比文本更大更大,我希望它恰好适合文本。 我怎么做到的?
要计算文本的高度,是否尝试过使用CTFramesetterSuggestFrameSizeWithConstraints
?
http://foobarpig.com/iphone/using-ctframesettersuggestframesizewithconstraints-and-sizewithfont-to-calculate-text-height.html
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