Tôi đã tạo một danh mục cho UIApplicationvới visibleViewControllerstài sản. Ý tưởng chính là khá đơn giản. Tôi quẹt viewDidAppearvà viewDidDisappearphương pháp trong UIViewController. Trong viewDidAppearphương thức viewControll được thêm vào stack. Trong viewDidDisappearphương thức viewControll được gỡ bỏ khỏi stack. NSPointerArrayđược sử dụng thay vì NSArrayđể lưu trữ UIViewControllercác tài liệu tham khảo yếu . Cách tiếp cận này hoạt động cho bất kỳ hệ thống phân cấp viewControllers.
Ứng dụng + VisibleViewControllers.h
#import <UIKit/UIKit.h>
@interface UIApplication (VisibleViewControllers)
@property (nonatomic, readonly) NSArray<__kindof UIViewController *> *visibleViewControllers;
@end
Ứng dụng + VisibleViewControllers.m
#import "UIApplication+VisibleViewControllers.h"
#import <objc/runtime.h>
@interface UIApplication ()
@property (nonatomic, readonly) NSPointerArray *visibleViewControllersPointers;
@end
@implementation UIApplication (VisibleViewControllers)
- (NSArray<__kindof UIViewController *> *)visibleViewControllers {
return self.visibleViewControllersPointers.allObjects;
}
- (NSPointerArray *)visibleViewControllersPointers {
NSPointerArray *pointers = objc_getAssociatedObject(self, @selector(visibleViewControllersPointers));
if (!pointers) {
pointers = [NSPointerArray weakObjectsPointerArray];
objc_setAssociatedObject(self, @selector(visibleViewControllersPointers), pointers, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}
return pointers;
}
@end
@implementation UIViewController (UIApplication_VisibleViewControllers)
+ (void)swizzleMethodWithOriginalSelector:(SEL)originalSelector swizzledSelector:(SEL)swizzledSelector {
Method originalMethod = class_getInstanceMethod(self, originalSelector);
Method swizzledMethod = class_getInstanceMethod(self, swizzledSelector);
BOOL didAddMethod = class_addMethod(self, originalSelector, method_getImplementation(swizzledMethod), method_getTypeEncoding(swizzledMethod));
if (didAddMethod) {
class_replaceMethod(self, swizzledSelector, method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod));
} else {
method_exchangeImplementations(originalMethod, swizzledMethod);
}
}
+ (void)load {
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
[self swizzleMethodWithOriginalSelector:@selector(viewDidAppear:)
swizzledSelector:@selector(uiapplication_visibleviewcontrollers_viewDidAppear:)];
[self swizzleMethodWithOriginalSelector:@selector(viewDidDisappear:)
swizzledSelector:@selector(uiapplication_visibleviewcontrollers_viewDidDisappear:)];
});
}
- (void)uiapplication_visibleviewcontrollers_viewDidAppear:(BOOL)animated {
[[UIApplication sharedApplication].visibleViewControllersPointers addPointer:(__bridge void * _Nullable)self];
[self uiapplication_visibleviewcontrollers_viewDidAppear:animated];
}
- (void)uiapplication_visibleviewcontrollers_viewDidDisappear:(BOOL)animated {
NSPointerArray *pointers = [UIApplication sharedApplication].visibleViewControllersPointers;
for (int i = 0; i < pointers.count; i++) {
UIViewController *viewController = [pointers pointerAtIndex:i];
if ([viewController isEqual:self]) {
[pointers removePointerAtIndex:i];
break;
}
}
[self uiapplication_visibleviewcontrollers_viewDidDisappear:animated];
}
@end
https://gist.github.com/medvedzzz/e6287b99011f2437ac0beb5a72a897f0
Phiên bản Swift 3
Ứng dụng + VisibleViewControllers.swift
import UIKit
extension UIApplication {
private struct AssociatedObjectsKeys {
static var visibleViewControllersPointers = "UIApplication_visibleViewControllersPointers"
}
fileprivate var visibleViewControllersPointers: NSPointerArray {
var pointers = objc_getAssociatedObject(self, &AssociatedObjectsKeys.visibleViewControllersPointers) as! NSPointerArray?
if (pointers == nil) {
pointers = NSPointerArray.weakObjects()
objc_setAssociatedObject(self, &AssociatedObjectsKeys.visibleViewControllersPointers, pointers, objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN_NONATOMIC)
}
return pointers!
}
var visibleViewControllers: [UIViewController] {
return visibleViewControllersPointers.allObjects as! [UIViewController]
}
}
extension UIViewController {
private static func swizzleFunc(withOriginalSelector originalSelector: Selector, swizzledSelector: Selector) {
let originalMethod = class_getInstanceMethod(self, originalSelector)
let swizzledMethod = class_getInstanceMethod(self, swizzledSelector)
let didAddMethod = class_addMethod(self, originalSelector, method_getImplementation(swizzledMethod), method_getTypeEncoding(swizzledMethod))
if didAddMethod {
class_replaceMethod(self, swizzledSelector, method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod))
} else {
method_exchangeImplementations(originalMethod, swizzledMethod);
}
}
override open class func initialize() {
if self != UIViewController.self {
return
}
let swizzlingClosure: () = {
UIViewController.swizzleFunc(withOriginalSelector: #selector(UIViewController.viewDidAppear(_:)),
swizzledSelector: #selector(uiapplication_visibleviewcontrollers_viewDidAppear(_:)))
UIViewController.swizzleFunc(withOriginalSelector: #selector(UIViewController.viewDidDisappear(_:)),
swizzledSelector: #selector(uiapplication_visibleviewcontrollers_viewDidDisappear(_:)))
}()
swizzlingClosure
}
@objc private func uiapplication_visibleviewcontrollers_viewDidAppear(_ animated: Bool) {
UIApplication.shared.visibleViewControllersPointers.addPointer(Unmanaged.passUnretained(self).toOpaque())
uiapplication_visibleviewcontrollers_viewDidAppear(animated)
}
@objc private func uiapplication_visibleviewcontrollers_viewDidDisappear(_ animated: Bool) {
let pointers = UIApplication.shared.visibleViewControllersPointers
for i in 0..<pointers.count {
if let pointer = pointers.pointer(at: i) {
let viewController = Unmanaged<AnyObject>.fromOpaque(pointer).takeUnretainedValue() as? UIViewController
if viewController.isEqual(self) {
pointers.removePointer(at: i)
break
}
}
}
uiapplication_visibleviewcontrollers_viewDidDisappear(animated)
}
}
https://gist.github.com/medvedzzz/ee6f4071639d987793977dba04e11399