Question

我正在尝试从服务器下载一些图像，然后将这些图像设置为某些UIButton的背景图像。

首先下载图片：

NSString *urlMag1 = [NSString stringWithFormat:@"http://myweb.com/i224_mag1.png"];
    NSString *urlMag2 = [NSString stringWithFormat:@"http://myweb.com/i224_mag2.png"];
    NSString *str = [NSString stringWithFormat:urlMag1,urlMag2,nil];

    NSData *data = [NSData dataWithContentsOfFile:str];
    NSString *path = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
    [data writeToFile:path atomically:YES];

    UIImage *imgMag1 = [UIImage imageNamed:@"i224_mag2.png"];
    [mag2 setBackgroundImage:imgMag1 forState:UIControlStateNormal];

但没有任何反应!!，如何检查这些图像是否在目录中以避免更多下载

如果你帮我解决这个问题，我将不胜感激。

谢谢！

EDITED @Fernando Cervantes

我创建了一个方法来设置这样的按钮BG图像，但我不知道为什么不起作用！

- (UIImage *)loadImages :(NSString *)fileNames ofType:(NSString *)extension inDirectory:(NSString *)directoryPath {

    [[NSFileManager defaultManager] fileExistsAtPath:[directoryPath stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.%@", fileNames, extension]]];
    return 0;
}

并设置BG图像：

- (void)buttonsBGImage {



    UIImage * bgMag2 = [self loadImages:@"i224_mag2" ofType:@"png" inDirectory:[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0]];

    [mag2 setBackgroundImage:bgMag2 forState:UIControlStateNormal];


}

但实际上没有任何反应！即使我检查文件，它在应用程序目录

Answer 1

[UIImage imageNamed:@"i224_mag2.png"]; // it is only for bundle. You should use 

[UIImage imageWithContentsOfFile:path]

或

 [UIImage imageWithData:data];

更新

我使用UIButton类的类别。

- (void)loadImage:(NSString *)URL withActivityIndicator:(BOOL)hasActivity refreshObject:(UIView *)refresh{

   // load image from cache cutted   
dispatch_queue_t concurrentQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
//this will start the image loading in bg
dispatch_async(concurrentQueue, ^{  

    NSData *image = [[NSData alloc] initWithContentsOfURL:[NSURL URLWithString:URL]];

    //this will set the image when loading is finished
    dispatch_async(dispatch_get_main_queue(), ^{
        UIImage *loadedImage = [UIImage imageWithData:image];

 // add image to cache cutted

        [self setImage:loadedImage forState:UIControlStateNormal];

    });
});

}

Answer 2

以下方法可能对您有所帮助。

保存

-(void) saveFile:(NSString *)fileName ofType:(NSString *)extension fromURL:(NSString *)fileIndexPath inDirectory:(NSString *)directoryPath { NSData * data = [NSData dataWithContentsOfURL:[NSURL URLWithString:fileIndexPath]]; [data writeToFile:[NSString stringWithFormat:@"%@/%@.%@", directoryPath, fileName, extension] atomically:YES]; }

检查

-(BOOL) checkIfFileExists:(NSString *)fileName ofType:(NSString *)extension inDirectoryPath:(NSString *)directoryPath { bool result; if ([[NSFileManager defaultManager] fileExistsAtPath:[directoryPath stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.%@", fileName, extension]]]) { result = TRUE; } else { result = FALSE; } return result; }

设置

UIButton * button = [[UIButton alloc] init]; UIImage * backgroundImage = [self loadImage:@"YourImageName" ofType:@"png" inDirectory:[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0]]; [button setImage:backgroundImage forState:UIControlStateNormal];

的 -Edited -

我相信您的问题是您在loadImages方法中返回0。而不是返回图像本身。

这就是我完成它的方式：

<强>加载

-(UIImage *) loadImage:(NSString *)fileName ofType:(NSString *)extension inDirectory:(NSString *)directoryPath { UIImage * result = [UIImage imageWithContentsOfFile:[NSString stringWithFormat:@"%@/%@.%@", directoryPath, fileName, extension]]; return result; }

Answer 3

您正在使用dataWithContentsOfFile: API创建NSData。你应该使用dataWithContentsOfURL代替。

    NSString *urlMag1 = [NSString stringWithFormat:@"http://myweb.com/i224_mag1.png"];
    NSString *urlMag2 = [NSString stringWithFormat:@"http://myweb.com/i224_mag2.png"];


    NSData *image1 = [NSdata contentsOfURL:[NSURL URLWithString:urlMag1]];

    NSData *image2 = [NSdata contentsOfURL:[NSURL URLWithString:urlMag2]];


    [mag2 setBackgroundImage:imgMag1 forState:UIControlStateNormal];

通常[NSdata contentsOfURL:[NSURL URLWithString:urlMag1]];将冻结UI，直到图像下载完成。

下载图像和UIButton BG图像

3 个答案:

的 -Edited -