什么时候NSStringDrawingContext的actualScaleFactor改变? 该文件说: “如果您在minimumScaleFactor属性中指定了一个自定义值,则绘图完成时,此属性将包含用于绘制string的实际缩放因子值。” 我的代码: myButton.titleLabel!.font = UIFont(name: "AmericanTypewriter-Bold", size: 40) myButton.titleLabel?.adjustsFontSizeToFitWidth = true myButton.setTitle("\(textString)", forState: .Normal) let attributes = [NSFontAttributeName : myButton.titleLabel!.font] let attributedString = NSMutableAttributedString(string:textString, attributes:attributes) let context = NSStringDrawingContext() context.minimumScaleFactor = myButton.titleLabel!.minimumScaleFactor print("context: \(context.actualScaleFactor)") let resultingRect = attributedString.boundingRectWithSize(myButton.titleLabel!.bounds.size, options: .UsesLineFragmentOrigin, context: context) print("actual context after drawing: \(context.actualScaleFactor)") //want to get the font size […]