iOS：管理通用应用

Question

I created an app for iPad, so I have two different version of image, example:

image.png (for iPad 2 or iPad Mini-not retina)
image@2x.png (for iPad >= 3 and iPad mini-retina)

It' very easy.

Now I should to create an universal version of my app, so I created my new launch image, icon and some background for iphone size without @2x because I don't want consider iphone 3gs, so I don't set image for iphone with @2x. And it's all ok.

But my app is a game, so I have a lot of images that are fine also for my iphone version. The problem is that iphone 4, 4s, 5 and 5s take image with @2x, but for these device, especially for iphone 4 these image are very big, and I have some memory leak with crashes. Now, my question is: is there a way, if device is retina, to take image that don't have the "@2x"??

Answer 1

Sure, just manage opening the images yourself.

For instance, I wanted to have a method like "imageNamed" but did not want the caching that imageNamed does, so I wrote my own. This isn't the function you want, but it illustrates the concept and you can make up your own rules. It isn't a huge amount of work to do your own implementation. If you wanted the caching of imageNamed, just use imageNamed to open the image that you eventually decide to use.

// An "uncached" version of -imageNamed.
// It looks for the scale-and-idiom suffixes @2x, ~ipad, and @2x~ipad
// and preferentially loads the specific version if it is available.
+ (UIImage *)imageNamedUncached:(NSString *)name {
    NSString *tryName;
    NSString *nonRetinaiPadTryName = @"";
    NSArray *parts = [name componentsSeparatedByString:@"."];
    if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) {
        if ([[UIScreen mainScreen] scale] == 1.0) {
            // non-retina
            tryName = [parts[0] stringByAppendingString:@"~ipad"];
            tryName = [tryName stringByAppendingString:@"."];
            tryName = [tryName stringByAppendingString:parts[1]];
        } else {
            // retina
            tryName = [parts[0] stringByAppendingString:@"@2x~ipad"];
            tryName = [tryName stringByAppendingString:@"."];
            tryName = [tryName stringByAppendingString:parts[1]];
            nonRetinaiPadTryName = [parts[0] stringByAppendingString:@"~ipad"];
            nonRetinaiPadTryName = [nonRetinaiPadTryName stringByAppendingString:@"."];
            nonRetinaiPadTryName = [nonRetinaiPadTryName stringByAppendingString:parts[1]];
        }
    } else {
        // iPhone
        if ([[UIScreen mainScreen] scale] == 1.0) {
            // non-retina
            tryName = name;
        } else {
            // retina
            tryName = [parts[0] stringByAppendingString:@"@2x"];
            tryName = [tryName stringByAppendingString:@"."];
            tryName = [tryName stringByAppendingString:parts[1]];        }
    }
    NSString *path = [[NSBundle mainBundle] pathForResource:tryName ofType:nil];
    //NSLog(@"For tryName %@ I get path %@",tryName, path);
    if ( ! path) {
        // If this is a retina iPad we made a non-retina try name -- so check that
        if ( ! [nonRetinaiPadTryName isEqualToString: @""]) {
            path = [[NSBundle mainBundle] pathForResource:nonRetinaiPadTryName ofType:nil];
            //NSLog(@"For non-retina ipad try name %@ I get path %@",nonRetinaiPadTryName, path);
        }
        if ( ! path) {
        // Try the unmodified name
        path = [[NSBundle mainBundle] pathForResource:name ofType:nil];
            //NSLog(@"For base name %@ I get path %@",name, path);
        }
    }
    UIImage *pathImage = [UIImage imageWithContentsOfFile:path];
    return pathImage;
}