iphone - 应用程序在UIScrollview中加载太多图像时崩溃

Question

我正在创建一个应用程序，该应用程序加载了56张图像，总大小约为200MB，当我在UIScrollView中显示所有这些图像时，该应用程序花费的时间太长(大约6分钟)，有时会崩溃。

请为我提供一种使用UIView进行排序并一次加载1张图片的方法。图像保存在应用程序中。

Answer 1

如果您的图像 View 大小为320 * 416像素，则计算内存大小可能为320 * 416 * 200/1000000 =〜27 MB。

更好的选择是将图像缩放到320 * 416像素:

- (UIImage *)imageByScalingProportionallyToSize:(CGSize)targetSize;

- (UIImage *)imageByScalingProportionallyToSize:(CGSize)targetSize {

    UIImage *sourceImage = self;
    UIImage *newImage = nil;

    CGSize imageSize = sourceImage.size;
    CGFloat width = imageSize.width;
    CGFloat height = imageSize.height;

    CGFloat targetWidth = targetSize.width;
    CGFloat targetHeight = targetSize.height;

    CGFloat scaleFactor = 0.0;
    CGFloat scaledWidth = targetWidth;
    CGFloat scaledHeight = targetHeight;

    CGPoint thumbnailPoint = CGPointMake(0.0,0.0);

    if (CGSizeEqualToSize(imageSize, targetSize) == NO) {

        CGFloat widthFactor = targetWidth / width;
        CGFloat heightFactor = targetHeight / height;

        if (widthFactor < heightFactor) 
            scaleFactor = widthFactor;
        else
            scaleFactor = heightFactor;

        scaledWidth  = width * scaleFactor;
        scaledHeight = height * scaleFactor;

        // center the image

        if (widthFactor < heightFactor) {
            thumbnailPoint.y = (targetHeight - scaledHeight) * 0.5; 
        } else if (widthFactor > heightFactor) {
            thumbnailPoint.x = (targetWidth - scaledWidth) * 0.5;
        }
    }


    // this is actually the interesting part:

    UIGraphicsBeginImageContext(targetSize);

    CGRect thumbnailRect = CGRectZero;
    thumbnailRect.origin = thumbnailPoint;
    thumbnailRect.size.width  = scaledWidth;
    thumbnailRect.size.height = scaledHeight;

    [sourceImage drawInRect:thumbnailRect];

    newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    if(newImage == nil) NSLog(@"could not scale image");


    return newImage ;
}