为按钮设置网络图片, 可以使用SDWebImage第三方库提供的UIButton+WebCache.h 分类 提供的以下方法:
[btn sd_setImageWithURL:btnUrl forState:UIControlStateNormal];
#import "UIButton+WebCache.h"
- (void)viewDidLoad {
[super viewDidLoad];
NSURL *btnUrl = [NSURL URLWithString:@"http://cdn2.jianshu.io/assets/web/logo-58fd04f6f0de908401aa561cda6a0688.png"];
UIButton *btn = [[UIButton alloc] initWithFrame:CGRectMake(60, 120, 180, 44)];
[btn setBackgroundColor:[UIColor colorWithRed:0.95 green:0.95 blue:0.95 alpha:1]];
[btn setTitle:@"进入简书" forState:UIControlStateNormal];
[btn setTitleColor:[UIColor orangeColor] forState:UIControlStateNormal];
[btn sd_setImageWithURL:btnUrl forState:UIControlStateNormal];
[self.view addSubview:btn];
}
然而,使用了默认的网络图片大小, 显示起来却是这样的, 我尝试了各种按钮的属性设置, 都没有把这个妖孽改成合适大小. (包括尝试了更改按钮的imageEdgeInsets 属性, 也没成功.)
默认网络图片大小是这样的.png
然后我想到了这样的方案: 下载下来的图片, 先调整图片的尺寸, 然后在去设置到按钮上, 同样, UIButton+WebCache.h 分类 提供的以下方法可以实现:
//这个方法提供了完成回调, 回调提供了下载下来的图片,这样我们就可以先更改这个图片的尺寸, 然后在设置给按钮使用.
[btn sd_setImageWithURL:btnUrl forState:UIControlStateNormal completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, NSURL *imageURL) {
[btn setImage:image forState:UIControlStateNormal];
}];
```
然后有了以下代码:
```
- (void)viewDidLoad {
[super viewDidLoad];
NSURL *btnUrl = [NSURL URLWithString:@"http://cdn2.jianshu.io/assets/web/logo-58fd04f6f0de908401aa561cda6a0688.png"];
UIButton *btn = [[UIButton alloc] initWithFrame:CGRectMake(60, 120, 180, 44)];
[btn setBackgroundColor:[UIColor colorWithRed:0.95 green:0.95 blue:0.95 alpha:1]];
[btn setTitle:@"进入简书" forState:UIControlStateNormal];
[btn setTitleColor:[UIColor orangeColor] forState:UIControlStateNormal];
[btn sd_setImageWithURL:btnUrl forState:UIControlStateNormal completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, NSURL *imageURL) {
image = [self imageByScalingToSize:CGSizeMake(80, 36) ForImage:image];
[btn setImage:image forState:UIControlStateNormal];
}];
[self.view addSubview:btn];
}
- (UIImage *)imageByScalingToSize:(CGSize)targetSize ForImage:(UIImage *)image{
//用作3倍率缩放, 保证图片不失真
targetSize = CGSizeMake(targetSize.width*3, targetSize.height*3);
UIImage *sourceImage = image;
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");
UIImage *image3Scale = [[UIImage alloc] initWithData:UIImagePNGRepresentation(newImage) scale:3.0];
return image3Scale;
}
```
效果:
