cell imageview的属性是readonly
所以不可变更
可以用这种方法改
UIImage *icon = [UIImage imageWithName:@"xxxxx"];
CGSize itemSize = CGSizeMake(30, 30);
UIGraphicsBeginImageContextWithOptions(itemSize, NO,0.0);
CGRect imageRect = CGRectMake(0.0, 0.0, itemSize.width, itemSize.height);
[icon drawInRect:imageRect];
cell.imageView.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
2:最后.m设置实现属性 @synthesize