ios - NSCache UIImage 数据从一个 ViewController 传递到另一个 ViewController

Question

让我先解释一下场景。我有一个 UIScrollView 并在其中添加一些 UIButton 作为 subView。在这些按钮中，我正在加载一些图像(来自远程服务器)。我使用 NSMutableURLRequest 加载所有图像并保存在 NSCache 中。由于加载需要很长时间，这就是为什么我想使用这个NSCache，这样在其他ViewController中，我就不必从远程服务器再次加载它们。因此，我通过 Segue 将 NSCache 传递给另一个 ViewController。不过，我不确定 NSCache 是否可行？请让我知道。我在下面为您提供了我的代码，以便您可以查看它。

非常感谢。祝你有美好的一天。

MainViewController.h:

@interface MainViewController : UIViewController
{
    NSTimer *timer;
    int counter;
}

@property (strong, nonatomic) IBOutlet UIButton *adButtonOutLet;
@property (strong, nonatomic) IBOutlet UIScrollView *scrollView;
@property (nonatomic, strong) AdInfo *currentAd;
@property (nonatomic, retain) IBOutlet UIActivityIndicatorView *activityIndicator;
@property (nonatomic, retain) AdParser *adParser;
@property (nonatomic, strong) NSMutableArray *adsListArray;
@property (nonatomic, strong) NSMutableArray *displayArray;

@property (nonatomic, strong) NSCache *imageCache;

MainViewController.m:

-(void)startAnimation:(id)data
{
    activityIndicator = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];

    activityIndicator.frame = CGRectMake(140.0, 525.0, 40.0, 40.0);
    [self.view addSubview:activityIndicator];

    [activityIndicator startAnimating];
    activityIndicator.hidesWhenStopped=YES;
}

- (void)viewDidLoad
{
    [super viewDidLoad];
    [self startAnimation:nil];
    self.imageCache = [[NSCache alloc] init];

    [self performSelector:@selector(loadData) withObject:nil afterDelay:0.5];
    counter = 0;
    timer = [NSTimer scheduledTimerWithTimeInterval:3.0 target: self selector: @selector(handleTimer:) userInfo: nil repeats: YES];
}

- (void)handleTimer:(NSTimer *)timer
{
    //NSLog(@"counter %i", counter);
    if (counter == [displayArray count])
    {
        [scrollView setContentOffset:CGPointMake(320, 0) animated:YES];
        counter = 0;
    }
    else
    {
        [scrollView setContentOffset:CGPointMake(counter*320, 0) animated:YES];
    }
    counter++;
}

-(void) loadData
{
    adParser = [[AdParser alloc] loadXMLByURL:getXMLURL];
    adsListArray = [adParser ads];
    displayArray = [[NSMutableArray alloc] init];

    for (AdInfo *adInfo1 in adsListArray)
    {
        AdInfo *adInfo2 = [[AdInfo alloc] init];
        [adInfo2 setBannerIconURL:adInfo1.bannerIconURL];
        [adInfo2 setBannerIconLink:adInfo1.bannerIconLink];
        [displayArray addObject:adInfo2];
    }
    [self loadScrollView];
    [activityIndicator stopAnimating];
}

-(void) loadScrollView
{
    [self.scrollView setScrollEnabled:YES];
    [self.scrollView setContentSize:CGSizeMake([displayArray count] * ScrollerWidth, ScrollerHight)];

    for (int i = 0; i < [displayArray count]; i++)
    {
        adButtonOutLet = [[UIButton alloc] initWithFrame:CGRectMake(i*320, 0, ButtonWidth, ButtonHight)];

        currentAd = [displayArray objectAtIndex:i];

        NSString *path = currentAd.bannerIconURL;
        NSURL *url = [NSURL URLWithString:path];
        NSMutableURLRequest *requestWithBodyParams = [NSMutableURLRequest requestWithURL:url];
        NSData *imageData = [NSURLConnection sendSynchronousRequest:requestWithBodyParams returningResponse:nil error:nil];
        UIImage *originalImage = [UIImage imageWithData:imageData];

        UIImage *cachedImage =   [self.imageCache objectForKey:currentAd.bannerIconURL];
        if (cachedImage)
        {
            [adButtonOutLet setImage:cachedImage forState:UIControlStateNormal];
        }
        else
        {
            [self.imageCache setObject:originalImage forKey:currentAd.bannerIconURL];
            NSLog(@"tulon %@", self.imageCache);
            [adButtonOutLet setImage:originalImage forState:UIControlStateNormal];
        }

        adButtonOutLet.userInteractionEnabled= YES;
        [adButtonOutLet setTag:i];
        [adButtonOutLet addTarget:self action:@selector(goToURL:) forControlEvents:UIControlEventTouchUpInside];

        [self.scrollView addSubview:adButtonOutLet];
    }
}

-(IBAction)goToURL:(UIButton *)sender
{
    NSInteger indexValue = sender.tag;
    for (int i = 0; i < [displayArray count]; i++)
    {
        if (indexValue == i)
        {
            currentAd = [displayArray objectAtIndex:i];
            NSString *url = currentAd.bannerIconLink;
            [[UIApplication sharedApplication]  openURL:[NSURL URLWithString:url]];
        }
    }
}

-(void) prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if ([segue.identifier isEqualToString:@"goToSecondViewController"])
    {
        SecondViewController *secondViewController = [segue destinationViewController];
        [secondViewController setImageCache:imageCache];
        [secondViewController setDisplayArray:displayArray];
    }
}

SecondViewController.h:

@interface SecondViewController : UIViewController
{
    NSTimer *timer;
    int counter;
}

@property (strong, nonatomic) IBOutlet UIButton *adButtonOutLet;
@property (nonatomic, strong) AdInfo *currentAd;
@property (strong, nonatomic) IBOutlet UIScrollView *scrollView;
@property (nonatomic, strong) NSCache *imageCache;
@property (nonatomic, strong) NSMutableArray *displayArray;

SecondViewController.m:

- (void)viewDidLoad
{
    [super viewDidLoad];
    self.imageCache = [[NSCache alloc] init];
    [self performSelector:@selector(loadScrollView) withObject:nil afterDelay:0.5];
    counter = 0;
    timer = [NSTimer scheduledTimerWithTimeInterval:3.0 target: self selector: @selector(handleTimer:) userInfo: nil repeats: YES];
    NSLog(@"tulon %@", self.imageCache);
}

- (void)handleTimer:(NSTimer *)timer
{
    if (counter == [displayArray count])
    {
        [scrollView setContentOffset:CGPointMake(320, 0) animated:YES];
        counter = 0;
    }
    else
    {
        [scrollView setContentOffset:CGPointMake(counter*320, 0) animated:YES];
    }
    counter++;
}


-(void) loadScrollView
{
    [self.scrollView setScrollEnabled:YES];
    [self.scrollView setContentSize:CGSizeMake([displayArray count] * ScrollerWidth, ScrollerHight)];

    for (NSInteger i = 0; i < [displayArray count]; i++)
    {
        adButtonOutLet = [[UIButton alloc] initWithFrame:CGRectMake(i*320, 0, ButtonWidth, ButtonHight)];

        currentAd = [displayArray objectAtIndex:i];
        UIImage *cachedImage =   [self.imageCache objectForKey:currentAd.bannerIconURL];
        [adButtonOutLet setImage:cachedImage forState:UIControlStateNormal];


        adButtonOutLet.userInteractionEnabled= YES;
        [adButtonOutLet setTag:i];
        [adButtonOutLet addTarget:self action:@selector(goToURL:) forControlEvents:UIControlEventTouchUpInside];

        [self.scrollView addSubview:adButtonOutLet];
    }
}

-(IBAction)goToURL:(UIButton *)sender
{
    NSInteger indexValue = sender.tag;
    for (int i = 0; i < [displayArray count]; i++)
    {
        if (indexValue == i)
        {
            currentAd = [displayArray objectAtIndex:i];
            NSString *url = currentAd.bannerIconLink;
            [[UIApplication sharedApplication]  openURL:[NSURL URLWithString:url]];
        }
    }
}

添加:
在 SecondViewController 中，我再次创建了 NSCache *imageCache;，当我为它创建 NSlog 时，没有得到任何值。我想我在这里遗漏了一些东西。或者没有遵循适当的方式。

Answer 1

In SecondViewController I create NSCache *imageCache; again

不需要

self.imageCache = [[NSCache alloc] init];

去掉这一行，应该可以了