UIAppearance not taking effect on UILabels created programmatically

问题

We have extended UILabel to be able to apply standard fonts and colors for all uses of a given label type in our apps. Eg.

@interface UILabelHeadingBold : UILabel
@end

In our AppDelegate, we apply fonts and colors like this

[[UILabelHeadingBold appearance] setTextColor:<some color>];
[[UILabelHeadingBold appearance] setFont:<some font>];

When adding a UILabel in our XIB's, we can now select the class to be of type UILabelHeadingBold, and it works as expected. The label is shown with the correct font and color, as specified in our AppDelegate.

However, if we create a label programmatically, eg.

UILabelHeadingBold *headingLabel = [[UILabelHeadingBold alloc] initWithFrame:CGRectMake(10, 10, 100, 30)];
[self.mainView addSubview:headingLabel];

the UILabel does not get the expected font/color applied. We have to manually apply these attributes.

Is there a way to make UIAppearance take effect on programatically created UI elements, or does it only work when used within XIB's?

回答1:

From Apple documentation :

To support appearance customization, a class must conform to the UIAppearanceContainer protocol and relevant accessor methods must be marked with UI_APPEARANCE_SELECTOR.

For example in UINavigationBar.h, tintColor is marked with UI_APPEARANCE_SELECTOR

@property(nonatomic,retain) UIColor *tintColor UI_APPEARANCE_SELECTOR;

But in UILabel.h you can see that the textColor and font propertys are not marked with UI_APPEARANCE_SELECTOR but somehow it works when added in Interface Builder (following the documentation it shouldn't work at all).

回答2:

Simple hack that is working for me with no issues is to create a category with a UIAppearance setter that modifies UILabel properties.

Following UIAppearance conventions I created a method:

- (void)setTextAttributes:(NSDictionary *)numberTextAttributes;
{
    UIFont *font = [numberTextAttributes objectForKey:UITextAttributeFont];
    if (font) {
        self.font = font;
    }
    UIColor *textColor = [numberTextAttributes objectForKey:UITextAttributeTextColor];
    if (textColor) {
        self.textColor = textColor;
    }
    UIColor *textShadowColor = [numberTextAttributes objectForKey:UITextAttributeTextShadowColor];
    if (textShadowColor) {
        self.shadowColor = textShadowColor;
    }
    NSValue *shadowOffsetValue = [numberTextAttributes objectForKey:UITextAttributeTextShadowOffset];
    if (shadowOffsetValue) {
        UIOffset shadowOffset = [shadowOffsetValue UIOffsetValue];
        self.shadowOffset = CGSizeMake(shadowOffset.horizontal, shadowOffset.vertical);
    }
}

In UILabel category:

@interface UILabel (UISS)

- (void)setTextAttributes:(NSDictionary *)numberTextAttributes UI_APPEARANCE_SELECTOR;

@end

I'm still trying to figure out why the original setter does not work.

回答3:

I was having this exact same issue, but in Swift. A custom UILabel's appearance would work if added from a storyboard, but not if added from code.

Here's a solution I found in Swift that's working for me:

class MyLabel: UILabel { }

extension UILabel {
    @objc dynamic var customFont: UIFont! {
        get { return self.font }
        set { self.font = newValue }
    }

    @objc dynamic var customColor: UIColor! {
        get { return self.textColor }
        set {  self.textColor = newValue }
    }
}

Then add these lines where you configure your app appearance:

MyLabel.appearance().customFont = UIFont.systemFont(ofSize: 20)
MyLabel.appearance().customColor = UIColor.magenta

回答4:

@robert.wijas solution works great !

For iOS 7 and upwards I had to update the key since the one he used are deprecated for 7+ :

- (void)setTextAttributes:(NSDictionary *)numberTextAttributes;
{
    UIFont *font = [numberTextAttributes objectForKey:NSFontAttributeName];
    if (font) {
        self.font = font;
    }
    UIColor *textColor = [numberTextAttributes objectForKey:NSForegroundColorAttributeName];
    if (textColor) {
        self.textColor = textColor;
    }
    UIColor *textShadowColor = [numberTextAttributes objectForKey:NSShadowAttributeName];
    if (textShadowColor) {
        self.shadowColor = textShadowColor;
    }
    NSValue *shadowOffsetValue = [numberTextAttributes objectForKey:NSShadowAttributeName];
    if (shadowOffsetValue) {
        UIOffset shadowOffset = [shadowOffsetValue UIOffsetValue];
        self.shadowOffset = CGSizeMake(shadowOffset.horizontal, shadowOffset.vertical);
    }
}

回答5:

A workaround that I've used is to manually apply the color from the appearance that is set:

let label = UILabel()
label.textColor = UILabel.appearance().textColor

This way you don't need to reference anything new, or explicitly define the color. This also works for context specific coloring:

label.textColor = UILabel.appearance(whenContainedInInstancesOf:[MyView.self]).textColor

来源：https://stackoverflow.com/questions/11308379/uiappearance-not-taking-effect-on-uilabels-created-programmatically

标签

ios

appearance

uiappearance