https://www.jianshu.com/p/46b174babe09

iOS13 适配 夜间模式与其他

• 夜间模式
• 其他问题:presentViewController
  KVC似有对象

一 ：夜间/深色模式 DarkMode

夜间模式是iOS13的重要更新之一，随之而来的是我们能从系统设置中“显示与亮度”中选择“浅色”、“深色”两种模式，并且可以设置自动切换。（“控制中心”亮度调节中也可直接调节）

已知问题：在系统设置为深色模式时候，无法更改StateBar颜色

1. 如果不想适配深色模式的两种方式,任选
   （1）.直接在项目的plist文件中设置

参考:https://developer.apple.com/library/archive/documentation/General/Reference/InfoPlistKeyReference/Articles/iPhoneOSKeys.html#//apple_ref/doc/uid/TP40009252-SW44

    <key>UIUserInterfaceStyle</key>
    <string>Light</string>

（2）.在每个UIViewController或者BaseViewController(如果自己有的话)，中设置

if (@available(iOS 13.0, *)){
       self.overrideUserInterfaceStyle = UIUserInterfaceStyleLight;
    }

1. 适配深色模式
   首先我们要看一下显示模式的枚举值

typedef NS_ENUM(NSInteger, UIUserInterfaceStyle) {
    UIUserInterfaceStyleUnspecified,
    UIUserInterfaceStyleLight,
    UIUserInterfaceStyleDark,
} API_AVAILABLE(tvos(10.0)) API_AVAILABLE(ios(12.0)) API_UNAVAILABLE(watchos);

当前API还没有提供浅色/深色模式切换时的通知，但是为UIColor添加了新方法：
+ (UIColor *)colorWithDynamicProvider:(UIColor * (^)(UITraitCollection *))dynamicProvider;
该方法通过一个block返回颜色,根据其中UITraitCollection参数,我们可以获取到当前系统的UIUserInterfaceStyle. 这个方法会在每次系统模式改变后回调,所以我想,我可以在一个颜色中去为当前界面做监听.

Xcode 11为xcassets带来更新以自动读取加载浅色/深色模式的资源,只要修改资源Appearances属性,来设置是否要支持浅色/深色模式,以及资源内容即可,[UIImage imageNamed:@""]会自动加载浅色/深色资源.

image.png

最后上一段 UIViewController 截图

vc.JPG

最后最后上一段 UIViewController 代码

#import "DarkModeViewController.h"

@interface DarkModeViewController ()
{
    UIImageView *_iv2;
    UIUserInterfaceStyle _userInterfaceStyle;
}
@end

@implementation DarkModeViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    __weak typeof(self)weakSelf = self;
    UIColor *backgroundColor = [UIColor colorWithDynamicProvider:^UIColor * _Nonnull(UITraitCollection * traitCollection) {
        self->_userInterfaceStyle = traitCollection.userInterfaceStyle;
        [weakSelf performSelector:@selector(traitCollectionChanged:) withObject:traitCollection];
        if (traitCollection.userInterfaceStyle == UIUserInterfaceStyleDark) {
            return [UIColor blueColor];
        }
        return [UIColor yellowColor];
    }];
    self.view.backgroundColor = backgroundColor;
    
    UIImageView *iv = ({
        UIImageView *imageView = [[UIImageView alloc] init];
        [imageView setBackgroundColor:[UIColor clearColor]];
        [imageView setFrame:CGRectMake(20, 100, 100, 100)];
        imageView.image = [UIImage imageNamed:@"icon_star"];
        imageView;
    });
    [self.view addSubview:iv];
    
    _iv2 = ({
        UIImageView *imageView = [[UIImageView alloc] init];
        [imageView setBackgroundColor:[UIColor clearColor]];
        [imageView setFrame:CGRectMake(20, 240, 100, 100)];
        imageView;
    });
    [self.view addSubview:_iv2];
    [self iv2updateImage];
}

- (void)traitCollectionChanged:(UITraitCollection *)traitCollection{
    NSLog(@"traitCollectionChanged:%ld",traitCollection.userInterfaceStyle);
    [self iv2updateImage];
    
}
- (void)iv2updateImage {
    NSLog(@"iv2updateImage:%ld",_userInterfaceStyle);
    if (_userInterfaceStyle == UIUserInterfaceStyleDark) {
        _iv2.image = [UIImage systemImageNamed:@"star.circle.fill"];
    }else{
        _iv2.image = [UIImage systemImageNamed:@"star.circle"];
    }
}
@end

二 ：其他问题

1. presentViewController
   modalPresentationStyle参数有 iOS12 之前的UIModalPresentationFullScreen改为了UIModalPresentationPageSheet,
   在需要presentViewController FullScreen样式,需要提前设置

2.可能存在问题的私有KVC (textField 的 Placeholder)
放弃使用 KVC 去修改,将修改
_placeholderLabel.textColor 和 _placeholderLabel.font
改为

    UITextField *_textField = [UITextField new];
    
    _textField.attributedPlaceholder = [[NSAttributedString alloc] initWithString:@"UITextField attributedPlaceholder"
                                                                       attributes:@{NSFontAttributeName:_textField.font,
                                                                                    NSForegroundColorAttributeName:[UIColor yellowColor]}];