我测试了一个使用自定义UIFont的应用。此字体用于可缩放的UILabel - 它具有CATiledLayer图层。
这是UILabel类的代码：
#import "ZoomableLabel.h"
@implementation ZoomableLabel
+ (Class)layerClass
{
return [CATiledLayer class];
}
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
// Initialization code
[self setupView];
}
return self;
}
//- (id)initWithCoder:(NSCoder *)aDecoder {
// self = [super initWithCoder:aDecoder];
// if (self) {
// // Initialization code
// [self setupView];
// }
// return self;
//}
-(void)awakeFromNib {
[super awakeFromNib];
[self setupView];
}
- (void)setupView {
CATiledLayer *layerForView = (CATiledLayer *)self.layer;
layerForView.levelsOfDetailBias = 3;
layerForView.levelsOfDetail = 1;
}
-(void)setText:(NSString *)value {
self.layer.contents = nil;
[super setText:value];
[self setNeedsDisplay];
}
-(void)setTextColor:(UIColor *)value {
self.layer.contents = nil;
[super setTextColor:value];
[self setNeedsDisplay];
}
@end
当我第一次在设备或模拟器上运行应用程序时（即应用程序首次在设备或模拟器上安装）我遇到了崩溃。然后这个崩溃再也不会发生！更新：崩溃发生非常随机（特别是在演示应用程序时...），但不仅仅是第一次。这是我从XCode获得的所有信息：
Thread 3 name: Dispatch queue: com.apple.root.default-priority
Thread 3 Crashed: 0 WebCore 0x333adbfa WTF::HashTable<WebCore::FontData const*, std::__1::pair<WebCore::FontData const*, WebCore::GlyphPageTreeNode*>, WTF::PairFirstExtractor<std::__1::pair<WebCore::FontData const*, WebCore::GlyphPageTreeNode*> >, WTF::PtrHash<WebCore::FontData const*>, WTF::HashMapValueTraits<WTF::HashTraits<WebCore::FontData const*>, WTF::HashTraits<WebCore::GlyphPageTreeNode*> >, WTF::HashTraits<WebCore::FontData const*> >::rehash(int) + 42
1 WebCore 0x333adcd4 WTF::HashTableAddResult<WTF::HashTableIterator<WebCore::FontData const*, std::__1::pair<WebCore::FontData const*, WebCore::GlyphPageTreeNode*>, WTF::PairFirstExtractor<std::__1::pair<WebCore::FontData const*, WebCore::GlyphPageTreeNode*> >, WTF::PtrHash<WebCore::FontData const*>, WTF::HashMapValueTraits<WTF::HashTraits<WebCore::FontData const*>, WTF::HashTraits<WebCore::GlyphPageTreeNode*> >, WTF::HashTraits<WebCore::FontData const*> > > WTF::HashTable<WebCore::FontData const*, std::__1::pair<WebCore::FontData const*, WebCore::GlyphPageTreeNode*>, WTF::PairFirstExtractor<std::__1::pair<WebCore::FontData const*, WebCore::GlyphPageTreeNode*> >, WTF::PtrHash<WebCore::FontData const*>, WTF::HashMapValueTraits<WTF::HashTraits<WebCore::FontData const*>, WTF::HashTraits<WebCore::GlyphPageTreeNode*> >, WTF::HashTraits<WebCore::FontData const*> >::add<WTF::HashMapTranslator<WTF::HashMapValueTraits<WTF::HashTraits<WebCore::FontData const*>, WTF::HashTraits<WebCore::GlyphPageTreeNode*> >, WTF::PtrHash<WebCore::FontData const*> >, WebCore::FontData const*, WebCore::GlyphPageTreeNode*>(WebCore::FontData const* const&, WebCore::GlyphPageTreeNode* const&) + 56
2 WebCore 0x333a5cac WebCore::GlyphPageTreeNode::getChild(WebCore::FontData const*, unsigned int) + 264
3 WebCore 0x333a55d8 WebCore::Font::glyphDataAndPageForCharacter(int, bool, WebCore::FontDataVariant) const + 528
4 WebCore 0x333a53b6 WebCore::Font::glyphDataForCharacter(int, bool, WebCore::FontDataVariant) const + 18
5 WebCore 0x333a4b36 WebCore::WidthIterator::advance(int, WebCore::GlyphBuffer*) + 398
6 WebCore 0x333a4794 WebCore::Font::floatWidthForSimpleText(WebCore::TextRun const&, WebCore::GlyphBuffer*, WTF::HashSet<WebCore::SimpleFontData const*, WTF::PtrHash<WebCore::SimpleFontData const*>, WTF::HashTraits<WebCore::SimpleFontData const*> >*, WebCore::GlyphOverflow*) const + 60
7 WebCore 0x333a4546 WebCore::Font::width(WebCore::TextRun const&, WTF::HashSet<WebCore::SimpleFontData const*, WTF::PtrHash<WebCore::SimpleFontData const*>, WTF::HashTraits<WebCore::SimpleFontData const*> >*, WebCore::GlyphOverflow*) const + 250
8 WebCore 0x333a60e0 WebCore::truncateString(WTF::String const&, float, WebCore::Font const&, unsigned int (*)(WTF::String const&, unsigned int, unsigned int, unsigned short*, bool), bool, float*, bool, float, bool) + 296
9 WebCore 0x333a5fac WebCore::StringTruncator::rightTruncate(WTF::String const&, float, WebCore::Font const&, WebCore::StringTruncator::EnableRoundingHacksOrNot, float&, bool, float) + 60
10 WebKit 0x375fc718 applyEllipsisStyle(WTF::String const&, WebEllipsisStyle, float, WebCore::Font const&, WebCore::StringTruncator::EnableRoundingHacksOrNot, float*, bool, float, bool) + 464
11 WebKit 0x375ff3a8 -[NSString(WebStringDrawing) __web_drawInRect:withFont:ellipsis:alignment:letterSpacing:lineSpacing:includeEmoji:truncationRect:measureOnly:renderedStringOut:drawUnderline:] + 5036
12 WebKit 0x375fdfe8 -[NSString(WebStringDrawing) __web_drawInRect:withFont:ellipsis:alignment:letterSpacing:lineSpacing:includeEmoji:truncationRect:measureOnly:renderedStringOut:] + 112
13 WebKit 0x375fdf64 -[NSString(WebStringDrawing) __web_drawInRect:withFont:ellipsis:alignment:letterSpacing:lineSpacing:includeEmoji:truncationRect:measureOnly:] + 108
14 WebKit 0x375fdee4 -[NSString(WebStringDrawing) _web_drawInRect:withFont:ellipsis:alignment:lineSpacing:includeEmoji:truncationRect:measureOnly:] + 108
15 WebKit 0x375fde64 -[NSString(WebStringDrawing) _web_sizeInRect:withFont:ellipsis:lineSpacing:] + 80
16 UIKit 0x353698c2 -[NSString(UIStringDrawing) sizeWithFont:constrainedToSize:lineBreakMode:lineSpacing:] + 122
17 UIKit 0x3535daa6 -[UILabel _legacy_drawTextInRect:baselineCalculationOnly:] + 594
18 UIKit 0x35321c5a -[UILabel _drawTextInRect:baselineCalculationOnly:] + 162
19 UIKit 0x35320a26 -[UILabel drawTextInRect:] + 446
20 UIKit 0x35320860 -[UILabel drawRect:] + 68
21 UIKit 0x3531fd20 -[UIView(CALayerDelegate) drawLayer:inContext:] + 360
22 QuartzCore 0x37b84bb8 -[CALayer drawInContext:] + 108
23 QuartzCore 0x37c62624 tiled_layer_render(_CAImageProvider*, unsigned int, unsigned int, unsigned int, unsigned int, void*) + 1416
24 QuartzCore 0x37bd755c CAImageProviderThread(unsigned int*, bool) + 508
25 libdispatch.dylib 0x37b5e95c _dispatch_root_queue_drain + 248
26 libdispatch.dylib 0x37b5eabc _dispatch_worker_thread2 + 80
27 libsystem_c.dylib 0x38862a0e _pthread_wqthread + 358
28 libsystem_c.dylib 0x388628a0 start_wqthread + 4
有人对此有任何想法吗？我认为这种崩溃不会发生在iOS 5设备上......
答案 0 :(得分：2)
以下是我对Summon的回答，它使用Core Text来解决英语以外的语言问题（尽管我只测试了瑞典语）和奇怪的字体符号。请注意，它使用initWithCoder，因为我正在使用StoryBoard。它还显示了如何将文本水平居中放置在标签中（垂直方向运气较差，我只需要测试到正确位置的方式）。
部首：
#import <UIKit/UIKit.h>
#import <QuartzCore/QuartzCore.h>
@interface DNLabel : UILabel
@end
实现：
#import "DNLabel.h"
#import <CoreText/CoreText.h>
@implementation DNLabel
+ (Class)layerClass
{
return [CATiledLayer class];
}
- (id)initWithCoder:(NSCoder *)aDecoder
{
self = [super initWithCoder:aDecoder];
if (self)
{
[self setupView];
}
return self;
}
-(void)awakeFromNib
{
[super awakeFromNib];
[self setupView];
}
- (void)setupView {
CATiledLayer *layerForView = (CATiledLayer *)self.layer;
layerForView.levelsOfDetailBias = 10;
layerForView.levelsOfDetail = 10;
}
// LEAVE IT EMPTY
-(void)drawRect:(CGRect)r
{
// UIView uses the existence of -drawRect: to determine if should allow its CALayer
// to be invalidated, which would then lead to the layer creating a backing store and
// -drawLayer:inContext: being called.
// By implementing an empty -drawRect: method, we allow UIKit to continue to implement
// this logic, while doing our real drawing work inside of -drawLayer:inContext:
}
// These calls inside this method are thread SAFE
-(void)drawLayer:(CALayer*)layer inContext:(CGContextRef)context
{
// Core Text version
CTFontRef ctFont = CTFontCreateWithName((__bridge CFStringRef)self.font.fontName,
self.font.pointSize,
NULL);
// set color
CGColorRef color = [[[UIColor blackColor] colorWithAlphaComponent:0.75f] CGColor];
// pack it into attributes dictionary
NSDictionary *attributesDict = [NSDictionary dictionaryWithObjectsAndKeys:
(id)CFBridgingRelease(ctFont), (id)kCTFontAttributeName,
color, (id)kCTForegroundColorAttributeName,
nil, (id)kCTUnderlineStyleAttributeName, nil];
// make the attributed string
NSAttributedString *stringToDraw = [[NSAttributedString alloc] initWithString:self.text
attributes:attributesDict];
// flip the coordinate system
CGContextSetTextMatrix(context, CGAffineTransformIdentity);
CGContextTranslateCTM(context, 0, self.bounds.size.height);
CGContextScaleCTM(context, 1.0, -1.0);
// check size of text and set position centered horizontally
CGSize size = [self.text sizeWithFont:self.font];
CGContextSetTextPosition(context, self.bounds.size.width/2 - size.width/2, 1);
// draw
CTLineRef line = CTLineCreateWithAttributedString(
(CFAttributedStringRef)CFBridgingRetain(stringToDraw));
CTLineDraw(line, context);
}
@end
答案 1 :(得分：1)
这些是基于CATiledLayer的可缩放标签的.h和.m类，它们永远不会崩溃：
部首：
#import <QuartzCore/QuartzCore.h>
@interface ZoomableLabel : UILabel {
CGPoint textDrawPoint;
CGPoint shadowDrawPoint;
}
@end
实现：
#import "ZoomableLabel.h"
@implementation ZoomableLabel
+ (Class)layerClass
{
return [CATiledLayer class];
}
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
// Initialization code
[self setupView];
}
return self;
}
-(void)awakeFromNib {
[super awakeFromNib];
[self setupView];
}
- (void)setupView {
CATiledLayer *layerForView = (CATiledLayer *)self.layer;
layerForView.levelsOfDetailBias = 3;
layerForView.levelsOfDetail = 1;
textDrawPoint = CGPointMake(11, -22);
shadowDrawPoint = CGPointMake(10, -23);
if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) {
textDrawPoint = CGPointMake(11, -42);
shadowDrawPoint = CGPointMake(8, -46);
}
}
// DO NOT USER THESE METHODS ANYMORE
//-(void)setText:(NSString *)value {
//// self.layer.contents = nil;
// [super setText:value];
// [self setNeedsDisplayInRect:self.bounds];
//}
//
//-(void)setTextColor:(UIColor *)value {
//// self.layer.contents = nil;
// [super setTextColor:value];
// [self setNeedsDisplayInRect:self.bounds];
//}
// LEAVE IT EMPTY
-(void)drawRect:(CGRect)r
{
// UIView uses the existence of -drawRect: to determine if should allow its CALayer
// to be invalidated, which would then lead to the layer creating a backing store and
// -drawLayer:inContext: being called.
// By implementing an empty -drawRect: method, we allow UIKit to continue to implement
// this logic, while doing our real drawing work inside of -drawLayer:inContext:
}
// These calls inside this method are thread SAFE
-(void)drawLayer:(CALayer*)layer inContext:(CGContextRef)context
{
// Do all your drawing here. Do not use UIGraphics to do any drawing, use Core Graphics instead.
CGContextScaleCTM(context, 1.0f, -1.0f);
CGContextSelectFont(context, [self.font.fontName UTF8String], self.font.pointSize, kCGEncodingMacRoman);
CGContextSetTextDrawingMode(context, kCGTextFill);
// CGContextSetShouldAntialias(context, true);
CGContextSetFillColorWithColor(context, [[[UIColor blackColor] colorWithAlphaComponent:0.75f] CGColor]);
CGContextShowTextAtPoint(context, shadowDrawPoint.x, shadowDrawPoint.y, [self.text UTF8String], self.text.length);
CGContextSetFillColorWithColor(context, [self.textColor CGColor]);
CGContextShowTextAtPoint(context, textDrawPoint.x, textDrawPoint.y, [self.text UTF8String], self.text.length);
}
@end