CGContextSelectFont equivalent

问题

In iOS7 CGContextSelectFont is deprecated. Deprecation message says that I have to use Core Text, but I don't know which is the exact equivalent of this piece of code:

CGContextSelectFont(context, "Helvetica", kBarLabelSize, kCGEncodingMacRoman);
CGContextSetTextDrawingMode(context, kCGTextFill);
CGContextSetRGBFillColor(context, 0, 0, 0, 1.0);
CGContextSetTextMatrix (context, CGAffineTransformMake(1.0, 0.0, 0.0, -1.0, 0.0, 0.0));
CGContextShowTextAtPoint(context, barX, barY, [@"Some text" cStringUsingEncoding:NSUTF8StringEncoding], [barValue length]);

I've been able to create the font with this code:

CFMutableAttributedStringRef attrStr = CFAttributedStringCreateMutable(kCFAllocatorDefault, 0);
CTFontRef font = CTFontCreateWithName(CFSTR("Helvetica"), kBarLabelSize, NULL);
CFAttributedStringSetAttribute(attrStr, CFRangeMake(0, CFAttributedStringGetLength(attrStr)), kCTFontAttributeName, font);

But now haw can I "draw" a text with this font into the context?

回答1:

As best I can understand from your code, the exact equivalent is:

CGContextSetTextDrawingMode(context, kCGTextFill); // This is the default
[[UIColor blackColor] setFill]; // This is the default
[@"Some text" drawAtPoint:CGPointMake(barX, barY)
           withAttributes:@{NSFontAttributeName:[UIFont fontWithName:@"Helvetica"
                                                                size:kBarLabelSize]
                            }];

Note that your calls to CGContextSetTextDrawingMode and CGContextSetRGBFillColor are setting the values to the defaults. Your call to CGContextSetTextMatrix is not needed when using UIKit drawing like this.

I have no idea what [barValue length] is here, however. I'm assuming that you simply incorrectly used this for the length of @"Some text". (length is not the number of bytes which is what you need. What you probably meant was [barValue lengthOfBytesUsingEncoding:NSUTF8StringEncoding]).

Note that UIKit string drawing (seen here) wraps Core Text.

回答2:

I have found, at least in my case, the problem with the new NSString.drawAtPoint interface is that it may draw upside down, depending on how you are using the context.

An alternate is to use the Core Text methods, specifically the CTLine interface thusly:

NSDictionary *attribs = @{NSFontAttributeName:[UIFont fontWithName:@"Helvetica" size:14.0]};

NSAttributedString *fontStr = [[NSAttributedString alloc] initWithString:@"some text" attributes:attribs];

CTLineRef displayLine = CTLineCreateWithAttributedString( (__bridge CFAttributedStringRef)fontStr );
CGContextSetTextPosition( ctx, xPosition, yPosition );
CTLineDraw( displayLine, ctx );
CFRelease( displayLine );

回答3:

You probably can use the following to replace it.

1. CGContextSetFont
2. CGContextSetFontSize

来源：https://stackoverflow.com/questions/18969784/cgcontextselectfont-equivalent