ios - 当应用程序终止并在 iOS 中再次启动时，NSNotificationCenter 不会触发

Question

我有一个物流应用程序要求禁用屏幕录制，我不希望人们使用新的 iOS-11 功能来录制包含敏感数据的屏幕并将其公开。由于在 iOS 中无法禁用屏幕录制，因此我尝试通过检测 iOS11 屏幕录制功能打开或关闭来解决。我使用了 isCaptured 和 UIScreenCapturedDidChange 通知。代码如下:

   - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
  if (@available(iOS 11.0, *)) {
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(screenCaptureChanged) name:UIScreenCapturedDidChangeNotification object:nil];
    }

    return YES;
 }

所以逻辑是当屏幕录制开始时触发通知，并且在录制时将黑色放在视频上的逻辑发生，当录制停止时黑色被删除。当应用程序移动到 background 、 active 、 inactive 和 foreground 场景时，这工作正常。但是，当应用程序被终止(终止)而屏幕录制仍在进行时，以及当我们再次启动应用程序而屏幕录制仍在进行时，黑色不会覆盖屏幕。那么如何使用选择器方法再次调用通知选择器

Answer 1

检查 application:didFinishLaunchingWithOptions: 中屏幕的 isCaptured 属性的值，并相应地显示或隐藏覆盖 View 。

UIWindow+ScreenCapture.h:

#import <UIKit/UIKit.h>

NS_ASSUME_NONNULL_BEGIN

@interface UIWindow (ScreenCapture)

- (void)showOrHideContentDependingOnCapturedState;
- (void)hideContent;
- (void)showContent;

@end

NS_ASSUME_NONNULL_END

UIWindow+ScreenCapture.m:

#import "UIWindow+ScreenCapture.h"

@implementation UIWindow (ScreenCapture)

- (void)showOrHideContentDependingOnCapturedState {
    if (self.screen.isCaptured) {
        [self hideContent];
    } else {
        [self showContent];
    }
}

- (void)hideContent {
    UIView *blackView = [self viewWithTag:1234];
    if (!blackView) {
        blackView = [[UIView alloc] initWithFrame:self.bounds];
    }

    blackView.tag = 1234;
    blackView.backgroundColor = UIColor.blackColor;
    blackView.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;

    // This is important! If this is not set, then any new view added to
    // the window (like the root view controller's view) will be overtop of
    // `blackView`, which we don't want.
    blackView.layer.zPosition = 10000;

    [self addSubview:blackView];
}

- (void)showContent {
    [[self viewWithTag:1234] removeFromSuperview];
}

@end

AppDelegate.h:

#import <UIKit/UIKit.h>

@interface AppDelegate : UIResponder <UIApplicationDelegate>

@property (nullable, strong, nonatomic) UIWindow *window;

@end

AppDelegate.m:

#import "AppDelegate.h"
#import "UIWindow+ScreenCapture.h"

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    [[NSNotificationCenter defaultCenter] addObserver:self
                                             selector:@selector(checkIsBeingRecorded)
                                                 name:UIScreenCapturedDidChangeNotification
                                               object:nil];
    [self.window showOrHideContentDependingOnCapturedState];

    return YES;
}

- (void)checkIsBeingRecorded {
    for (UIWindow *window in UIApplication.sharedApplication.windows) {
        [window showOrHideContentDependingOnCapturedState];
    }
}

@end