单击选项卡后，相机/相册不会在 ios 上重新加载

Posted 2023-03-22

【中文标题】单击选项卡后，相机/相册不会在 ios 上重新加载

【英文标题】：camera / photo album doesn't reload on ios after the tab has been clicked once

【发布时间】：2014-05-17 06:39:05

【问题描述】：

我有一个 ios 应用程序，它有一个用于打开相机的选项卡按钮和另一个用于打开相册的按钮。它们第一次打开还不错，但如果您取消或转到另一个选项卡，相机和相册将无法第二次打开。

例如，这是相册视图控制器。我唯一改变的是viewDidLoad 方法和添加openPhotoAlbum 方法。我使用故事板添加标签。

PhotoAlbumViewController.m

#import "PhotoAlbumViewController.h"
#import "AppDelegate.h"

@interface PhotoAlbumViewController ()

@property (nonatomic, strong) AppDelegate *appDelegate;

@end

@implementation PhotoAlbumViewController

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil

    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) 
        // Custom initialization
    
    return self;


- (void)viewDidLoad

    [super viewDidLoad];
    // Do any additional setup after loading the view.

    [self openPhotoAlbum];


- (void)didReceiveMemoryWarning

    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.


/*
#pragma mark - Navigation

// In a storyboard-based application, you will often want to do a little preparation before navigation
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender

    // Get the new view controller using [segue destinationViewController].
    // Pass the selected object to the new view controller.

*/

- (IBAction)openPhotoAlbum

    UIImagePickerController *albumPicker = [[UIImagePickerController alloc] init];

    albumPicker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;

    albumPicker.delegate = self;

    [self presentViewController:albumPicker animated:YES completion:nil];


@end

第 1 步：我点击相册

第 2 步：第一次显示相册

第 3 步：取消

第 4 步：相册不显示

【参考方案1】：

使用标签栏控制器管理您的层次结构，您的视图控制器将在您第一次选择它们时创建。当它们被创建时，viewDidLoad 将被调用。

创建后，它们会一直存在，并在您再次选择其选项卡时重新出现。

更好的选择是使用viewWillAppear，它在第一次创建（viewDidLoad 之后）和UIViewController 的每次后续出现时都会调用。

- (void)viewDidLoad

//called only on initial creation and appearance
    [super viewDidLoad];
    // Do any additional setup after loading the view.


- (void)viewWillAppear:(BOOL)animated

//called on every appearance
    [super viewWillAppear:animated];
    [self openPhotoAlbum];

Here is a good SO answer了解UIViewController的生命周期