As pointed out, this post relates how to get the height, rather than the number of lines. To get the number of lines,
- Get the height for a single letter, e.g.
@"A".
- Divide the height of the string by the height obtained in 1 above.
E.g.
CGFloat unitHeight = [@"A" heightForWidth:width usingFont:font];
CGFloat blockHeight = [text heightForWidth:width usingFont:font];
NSInteger numberOfLines = ceilf(blockHeight / unitHeight);
// need to #include <math.h> for ^^^^^
As of iOS 7, the way of getting a label's desired height changed. To get the height, you can use the following code:
NSStringDrawingContext *context = [[NSStringDrawingContext alloc] init];
CGSize labelSize = (CGSize){width, FLT_MAX};
CGRect r = [self boundingRectWithSize:labelSize options:NSStringDrawingUsesLineFragmentOrigin attributes:@{NSFontAttributeName: font} context:context];
where the height is r.size.height. Note that font must be provided. You can put this into a category for NSString for convenience, e.g.
@implementation NSString (HeightCalc)
- (CGFloat)heightForWidth:(CGFloat)width usingFont:(UIFont *)font
{
NSStringDrawingContext *context = [[NSStringDrawingContext alloc] init];
CGSize labelSize = (CGSize){width, FLT_MAX};
CGRect r = [self boundingRectWithSize:labelSize options:NSStringDrawingUsesLineFragmentOrigin attributes:@{NSFontAttributeName: font} context:context];
return r.size.height;
}
@end
(Do memory management if not using ARC, btw.)
For iOS 6 and below:
Let's say you have a UILabel *myLabel and you want to find out the height of the label (with some tweaking, you can get the # of lines by dividing the height with some appropriate number which depends on the font size).
UILabel *myLabel;
CGSize labelSize = [myLabel.text sizeWithFont:myLabel.font
constrainedToSize:myLabel.frame.size
lineBreakMode:UILineBreakModeWordWrap];
CGFloat labelHeight = labelSize.height;
Hope that helps. If it doesn't work let me know and I'll dig further. Also, untested code, but worked from reference.
For a more complete example, here is code which I put in the viewDidLoad: method of a view controller:
[super viewDidLoad];
UILabel *myLabel = [[UILabel alloc] initWithFrame:CGRectMake(50,50,200,350)];
myLabel.numberOfLines = 0;
myLabel.lineBreakMode = UILineBreakModeWordWrap;
myLabel.text = @"This is some text in a UILabel which is long enough to wrap around the lines in said UILabel. This is a test, this is only a test.";
[self.view addSubview:myLabel];
CGSize labelSize = [myLabel.text sizeWithFont:myLabel.font
constrainedToSize:myLabel.frame.size
lineBreakMode:UILineBreakModeWordWrap];
CGFloat labelHeight = labelSize.height;
NSLog(@"labelHeight = %f", labelHeight);
[myLabel release];
The output from the NSLog goes:
2010-11-15 18:25:27.817 so_labelheight[728:307] labelHeight = 126.000000
