iOS-預加載頁面視圖控制器及其子視圖控制器

Question

加載應用程序的選項卡視圖時，我還將嘗試加載頁面視圖控制器並將其保存在內存中，以保持應用程序的生命周期。 頁面視圖是我的self.playerQueueViewController。

-(void)viewDidLoad{
   [super viewDidLoad];
 self.playerQueueViewController = [[UIStoryboard storyboardWithName:@"MusicPlayerQueue" bundle:nil] instantiateInitialViewController];
    self.playerQueueViewController.transitioningDelegate = self;
    self.playerQueueViewController.modalPresentationStyle = UIModalPresentationCustom;
}

現在，只有在我致電時，視圖才會加載，

-(void)centerButtonPressed:(id)sender
{
    [self presentViewController:self.playerQueueViewController animated:YES completion:nil];
}

如何在我的tabViewController加載后立即加載和加載頁面視圖控制器的子視圖控制器的視圖？ 我試圖將所有這些視圖控制器保存在內存中。

這是我設置pageViewController的方法。

當前正在發生的事情是，僅當我使用-（void）centerButtonPressed模態顯示pageViewController時，才會加載它。 當我調用-（void）goToPrevious，-（void）goToNext時，子視圖會被加載

@property (strong, nonatomic) SAMusicPlayerViewController *playerViewController;
@property (strong, nonatomic) SAQueueViewController *queueViewController;
@end

@implementation SAPageRootViewController

- (IBAction)dissmissArrowPressed:(UIButton *)sender
{
    [self dismissViewControllerAnimated:YES completion:nil];
}

#pragma mark - Setters and Getters

- (NSArray *)contentPageRestorationIDs
{
    if (!_contentPageRestorationIDs) {
        _contentPageRestorationIDs = @[@"Player", @"Queue",];
    }

    return _contentPageRestorationIDs;
}


- (void)viewDidLoad {
    [super viewDidLoad];

    // Create the page view controller.
    UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"MusicPlayerQueue" bundle:nil];
    self.pageViewController = [storyboard instantiateViewControllerWithIdentifier:@"PageViewController"];
    self.queueViewController = [storyboard instantiateViewControllerWithIdentifier:@"Queue"];
    self.queueViewController.rootViewController = self;
    self.playerViewController = [storyboard instantiateViewControllerWithIdentifier:@"Player"];
    self.playerViewController.rootViewController = self;

    NSLog(@"Page Root Load");

    // Instantiate the first view controller.

    [self.pageViewController setViewControllers:@[self.playerViewController]
                                      direction:UIPageViewControllerNavigationDirectionForward
                                       animated:NO
                                     completion:^(BOOL finished) {
                                         // Completion code
                                     }];

    // Add the page view controller to this root view controller.
    [self addChildViewController:self.pageViewController];
    [self.view addSubview:self.pageViewController.view];
    [self.pageViewController didMoveToParentViewController:self];

    [self.view bringSubviewToFront:self.dismissArrowButton];

}

#pragma mark - Public Methods
- (void)goToPreviousContentViewController
{
    // Get index of current view controller
    SAQueueViewController *currentViewController = self.queueViewController;
    currentViewController.currentButton.enabled = NO;

    UIViewController *previousViewController = self.playerViewController;


    [self.pageViewController setViewControllers:@[previousViewController]
                                      direction:UIPageViewControllerNavigationDirectionReverse
                                       animated:YES
                                     completion:^(BOOL finished) {
                                         currentViewController.currentButton.enabled = YES;
                                     }];
}

- (void)goToNextContentViewController
{
    // Get index of current view controller
    SAMusicPlayerViewController *currentViewController = self.playerViewController;
    currentViewController.queueButton.enabled = NO;

    UIViewController *nextViewController = self.queueViewController;

    [self.pageViewController setViewControllers:@[nextViewController]
                                      direction:UIPageViewControllerNavigationDirectionForward
                                       animated:YES
                                     completion:^(BOOL finished) {
                                         currentViewController.queueButton.enabled = YES;
                                     }];
}

更新：

現在，我可以像這樣加載pageViewController的頁面視圖和初始子視圖。 問題是我無法在初始加載時加載第二個子視圖控制器。

所有這些代碼都在我的tabViewController的viewDidLoad中

self.pageRootViewController = [[UIStoryboard storyboardWithName:@"MusicPlayerQueue" bundle:nil] instantiateInitialViewController];
self.pageRootViewController.transitioningDelegate = self;
self.pageRootViewController.modalPresentationStyle = UIModalPresentationCustom;


UIPageViewController *pageViewController = self.pageRootViewController.pageViewController;
UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"MusicPlayerQueue" bundle:nil];
pageViewController = [storyboard instantiateViewControllerWithIdentifier:@"PageViewController"];
self.queueViewController = [storyboard instantiateViewControllerWithIdentifier:@"Queue"];
self.queueViewController.rootViewController = self.pageRootViewController;
self.playerViewController = [storyboard instantiateViewControllerWithIdentifier:@"Player"];
self.playerViewController.rootViewController = self.pageRootViewController;

// Add the page view controller to this root view controller.
[self.pageRootViewController addChildViewController:pageViewController];
[self.pageRootViewController.view addSubview:pageViewController.view];
[pageViewController didMoveToParentViewController:self.pageRootViewController];
[self.pageRootViewController.view bringSubviewToFront:self.pageRootViewController.dismissArrowButton];

// Instantiate the first view controller.

[pageViewController setViewControllers:@[self.playerViewController, self.queueViewController]
                            direction:UIPageViewControllerNavigationDirectionReverse
                                   animated:NO
                                 completion:^(BOOL finished) {
                                     // Completion code
                                 }];

更新2：

好的，我的代碼完全按照我的要求工作。 但是，我不確定這是否是解決此問題的最佳方法。 好像還好 我唯一不喜歡的是調用[self.queueViewController view]

在tabBarController的viewDidLoad中

   self.pageRootViewController = [[UIStoryboard storyboardWithName:@"MusicPlayerQueue" bundle:nil] instantiateInitialViewController];
    self.pageRootViewController.transitioningDelegate = self;
    self.pageRootViewController.modalPresentationStyle = UIModalPresentationCustom;


    UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"MusicPlayerQueue" bundle:nil];
    UIPageViewController *pageViewController = [storyboard instantiateViewControllerWithIdentifier:@"PageViewController"];
    self.pageRootViewController.pageViewController = pageViewController;
    self.queueViewController = [storyboard instantiateViewControllerWithIdentifier:@"Queue"];
    self.queueViewController.rootViewController = self.pageRootViewController;
    [self.queueViewController view];
    self.playerViewController = [storyboard instantiateViewControllerWithIdentifier:@"Player"];
    self.playerViewController.rootViewController = self.pageRootViewController;

    self.pageRootViewController.queueViewController = self.queueViewController;
    self.pageRootViewController.playerViewController = self.playerViewController;

    // Add the page view controller to this root view controller.
    [self.pageRootViewController addChildViewController:pageViewController];
    [self.pageRootViewController.view addSubview:pageViewController.view];
    [pageViewController didMoveToParentViewController:self.pageRootViewController];
    [self.pageRootViewController.view bringSubviewToFront:self.pageRootViewController.dismissArrowButton];

    // Instantiate the first view controller.

    [pageViewController setViewControllers:@[self.playerViewController]
                                direction:UIPageViewControllerNavigationDirectionReverse
                                       animated:NO
                                     completion:^(BOOL finished) {
                                         // Completion code
                                     }];

Answer 1

一種做到這一點的方法（看起來像是一種破解），但是可以工作，它是訪問視圖控制器視圖的框架。

CGRect dontCareRect = myNewViewController.view.frame

這將強制VC的視圖加載。

Answer 2

如果確實需要預加載，請在ViewController上調用.view，這將強制加載。

預加載視圖是不必要的。 您可以對子視圖的加載進行動畫處理，以增強UX並保持性能。