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这是我第一次使用核心图形和文本，因此可能会做一些非常简单的事情，这是不正确的。我一直在阅读文档，试图看看我哪里出错，但看不到它，所以不知道是否有人可以帮我找出问题。核心文本 - 文本的位置不正确
我想在屏幕顶部绘制一个简单的小横幅信息，但是我想在横幅中显示的文本并未绘制在正确的位置。
在我看来，我创建了我的控制如下：
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
self.banner = [[Banner alloc] initWithFrame:CGRectMake(0,20,768,200)];
[self.view addSubview:self.banner];
}
控件代码如下：
#import <CoreText/CoreText.h>
#import "Banner.h"
@implementation Banner
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
// Initialization code
self.backgroundColor = [UIColor colorWithRed:0.9 green:0.9 blue:0.9 alpha:1];
}
return self;
}
// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect
{
// Get the graphics context.
CGContextRef context = UIGraphicsGetCurrentContext();
// Draw the banner border.
CGContextSaveGState(context);
UIColor *strokeColor = [UIColor blackColor];
CGContextSetStrokeColorWithColor(context, strokeColor.CGColor);
CGContextSetLineWidth(context, 5);
CGContextStrokeRect(context, CGRectMake(2,2,self.frame.size.width -4,100));
CGContextRestoreGState(context);
// Setup the text label & value.
NSString *addressLabelText = @"Address";
NSString *addressValue = @"123 Letsby Avenue\nSome Place\nSome City\nSome County\nSome Postcode";
UIFont *font = [UIFont fontWithName:@"Helvetica" size:14.0];
CGSize labelSize = [self getBoundsForString:addressLabelText usingFont:font];
CGSize valueSize = [self getBoundsForString:addressValue usingFont:font];
// So I want to Draw the label at X:10 Y:10 and the Value At X:65 Y:10
// So we get Something like:
// =============================
// || Address 123 letsby avenue
// || Some Place
// || Some City
// || Some County
// || Some Postcode
// =============================
CGRect labelBounds = CGRectMake(10,10,labelSize.width,labelSize.height);
// Move the address value over the margin width(10) + the label width + some spacing(5)
CGRect valueBounds = CGRectMake(10 + labelSize.width + 5, 10, valueSize.width, valueSize.height);
[self drawString: addressLabelText withFont: font inRect:labelBounds usingContext:context];
[self drawString: addressValue withFont: font inRect:valueBounds usingContext:context];
// The text hasn't drawn where i thought it should. Draw a rect there to make sure i had the right bounds
UIColor *rectFillColor = [UIColor colorWithRed:0 green:0 blue:1 alpha:0.3];
CGContextSaveGState(context);
CGContextSetFillColorWithColor(context, [rectFillColor CGColor]);
CGContextFillRect(context, labelBounds);
CGContextFillRect(context, valueBounds);
CGContextRestoreGState(context);
//Hmm that is drawing in the right place. Whats going wrong with drawing the text.
[self setNeedsDisplay];
}
-(void) drawString:(NSString*) string withFont:(UIFont*)font inRect:(CGRect)rect usingContext:(CGContextRef) context
{
CGContextSaveGState(context);
// flipping the coordinate system.
CGContextTranslateCTM(context, 0, 200); // The control is rendered in a frame 200 high.
CGContextScaleCTM(context, 1.0, -1.0);
CGContextSetTextMatrix(context, CGAffineTransformIdentity);
// Define the path we are going to draw the text on.
CGMutablePathRef path = CGPathCreateMutable();
CGPathAddRect(path, NULL, rect);
CFMutableAttributedStringRef attrString = CFAttributedStringCreateMutable(kCFAllocatorDefault, 0);
CFAttributedStringReplaceString (attrString, CFRangeMake(0, 0), (CFStringRef)string);
// Create the framesetter with the attributed string.
CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString(attrString);
CFRelease(attrString);
// Create a frame.
CTFrameRef frame = CTFramesetterCreateFrame(framesetter, CFRangeMake(0, 0), path, NULL);
// Draw the specified frame in the given context.
CTFrameDraw(frame, context);
CGContextRestoreGState(context);
CFRelease(frame);
CFRelease(path);
CFRelease(framesetter);
}
-(CGSize) getBoundsForString:(NSString *)string usingFont:(UIFont *)font
{
return [string boundingRectWithSize:CGSizeMake(999,999)
options:NSStringDrawingUsesLineFragmentOrigin
attributes:[NSDictionary dictionaryWithObject:font forKey:NSFontAttributeName]
context:nil].size;
}
@end
这样做的结果是横幅广告的画一些蓝色rects我期望的文字是，但文字实际上出现在横幅以外，我很困惑为什么。
https://www.dropbox.com/s/q2ap9tl4okaka49/Banner.png
