Question

我正在尝试创建一个方法，它将对UILabel起作用，但在CoreText中，这是我想要做的：

div

问题在于，当我运行应用程序时，它会停在下一行而不会抛出异常：

+(void)drawText:(NSString*)textToDraw
        inFrame:(CGRect)frameRect
       withFont:(NSString *)fontName
   andFontColor:(UIColor *)fontColor
    andFontSize:(float)fontSize{


    CFStringRef fontN = (__bridge CFStringRef)fontName;


    NSMutableAttributedString *string = [[NSMutableAttributedString alloc]
                                         initWithString:textToDraw];

    CTFontRef helvetica = CTFontCreateWithName(fontN, fontSize, NULL);

    [string addAttribute:(id)kCTFontAttributeName
                   value:(__bridge id)helvetica
                   range:NSMakeRange(0, [string length])];


    [string addAttribute:(id)kCTForegroundColorAttributeName
                   value:(id)fontColor.CGColor
                   range:NSMakeRange(0, [string length])];

    CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef)string);

    CGMutablePathRef framePath = CGPathCreateMutable();
    CGPathAddRect(framePath, NULL, frameRect);

    // Get the frame that will do the rendering.
    CFRange currentRange = CFRangeMake(0, 0);
    CTFrameRef frameRef = CTFramesetterCreateFrame(framesetter, currentRange, framePath, NULL);
    CGPathRelease(framePath);

    // Get the graphics context.
    CGContextRef    currentContext = UIGraphicsGetCurrentContext();

    // Put the text matrix into a known state. This ensures
    // that no old scaling factors are left in place.
    CGContextSetTextMatrix(currentContext, CGAffineTransformIdentity);


    // Core Text draws from the bottom-left corner up, so flip
    // the current transform prior to drawing.
    CGContextTranslateCTM(currentContext, 0, frameRect.origin.y*2);
    CGContextScaleCTM(currentContext, 1.0, -1.0);

    // Draw the frame.
    CTFrameDraw(frameRef, currentContext);

    CGContextScaleCTM(currentContext, 1.0, -1.0);
    CGContextTranslateCTM(currentContext, 0, (-1)*frameRect.origin.y*2);


    CFRelease(frameRef);
    CFRelease(framesetter);

}

更新

我删除了一些不在此帖子中的额外行后解决了崩溃问题。但是我仍然需要一些帮助来调整这个方法来接受行数和换行模式（NSLineBreakByWordWrapping，NSLineBreakByTruncatingTail ..）

Answer 1

在弄清楚崩溃的原因之后，我在方法的开头添加了下一行：

textToDraw = [self getDisplayedStringInFrame:frameRect.size
                                         andFont:[UIFont fontWithName:fontName size:fontSize]
                                       andString:textToDraw];

并添加了这个额外的方法来处理我感兴趣的女巫的NSLineBreakByTruncatingTail效果：

+ (NSString *) getDisplayedStringInFrame:(CGSize)size andFont:(UIFont *)font andString:(NSString *)str{

    NSString *written = @"";

    int i = 0;
    int currentWidth = 0;
    NSString *nextSetOfString = @"";

    while (1)
    {
        NSRange range;
        range.location = i;
        range.length = 1;

        NSString *nextChar = [str substringWithRange:range];
        nextSetOfString = [nextSetOfString stringByAppendingString:nextChar];

        CGSize requiredSize = [nextSetOfString sizeWithFont:font constrainedToSize:CGSizeMake(NSIntegerMax, NSIntegerMax)];
        currentWidth = requiredSize.width;

        if(size.width >= currentWidth && size.height >= requiredSize.height)
        {
            written = [written stringByAppendingString:nextChar];
        }
        else
        {
            break;
        }
        i++;
    }

    written = [written substringToIndex:[written length] - 2];
    written = [written stringByAppendingString:@".."];

    return written;

}

使用CoreText在框架中绘制文本会导致崩溃

1 个答案: