NSCache UIImage 数据从 oneViewController 传递到 anotherViewController

Posted 2023-02-23

【中文标题】NSCache UIImage 数据从 oneViewController 传递到 anotherViewController

【英文标题】：NSCache UIImage data passing from oneViewController to anotherViewController

【发布时间】：2014-09-09 07:16:29

【问题描述】：

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，我不必从远程服务器再次加载它们。所以，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。我在下面给你我的代码，你可以看看它。

提前非常感谢。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]];
        
    

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

【参考方案1】：

在 SecondViewController 我创建 NSCache *imageCache;再次

不需要

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

删除这一行，它应该可以工作

【讨论】：

我明白了。 :D 当我在SecondViewController 中alloc 和init 时，它会创建一个新的imageCache。 :) Bohut shukriya。

完全正确。你说的:)