1.UITapGestureRecognizer传值
在对UIView等添加手势时，若想通过UITapGestureRecognizer传值，那么可以传tag
UITapGestureRecognizer *singleTap = [[UITapGestureRecognizeralloc] initWithTarget:selfaction:@selector(UesrClicked:)]; singleTap.view.tag = i; [imageView addGestureRecognizer:singleTap];然后根据tag做不同操作
2.同一个View里边添加两个collectionView时，即使这两个collectionView的layout是一样的，也不能公用同一个layout，否则会出bug，不一定崩溃，但也会出现其他问题。
3.遍历比较两个数组，可以用谓词NSPredicate。下面用例子说明
筛选arrayContents包含了哪些arrayFilter元素
self.arrayFilter = [NSArray arrayWithObjects:@"pict", @"blackrain", @"ip", nil]; self.arrayContents = [NSMutableArray arrayWithObjects:@"I am a picture.", @"I am a guy", @"I am gagaga", @"pict", @"iphone", nil];有三种方法来实现，最原始的使用两个for循环，最简洁的是用NSPredicate
//原始方法,两个for -(void)emunateArrTwoFor{ for (NSString *content in self.arrayContents) { for (NSString *filter in self.arrayFilter) { if ([filter isEqualToString:content]) { NSLog(@"相同元素为%@",content); } } } } //改进方法,一个for -(void)emunateArrOneFor{ NSArray *temp = [NSArray array]; for (NSUInteger i=0; i<self.arrayFilter.count; i++) { NSString *filter = [self.arrayFilter objectAtIndex:i]; NSPredicate *predict = [NSPredicate predicateWithFormat:@"self = %@",filter]; temp = [self.arrayContents filteredArrayUsingPredicate:predict]; if (temp.count > 0) { NSLog(@"-----%@",temp); } } } //最简洁方法，没有for -(void)emunateArrNoFor{ NSPredicate *predict = [NSPredicate predicateWithFormat:@"self in %@",self.arrayFilter]; NSArray *temp = [self.arrayContents filteredArrayUsingPredicate:predict]; NSLog(@"+++++%@",temp); }打印结果为
NSPredicate的关键词有in，contains，=，>，<等
4.UICollectionViewCell上有btn，btn如何获取cell的indexPath。可以这样来，这是苹果官方的做法
[cell.btn addTarget:self action:@selector(clickCatoryBtn:) forControlEvents:UIControlEventTouchUpInside]; -(void)clickCatoryBtn:(id)sender{ CGPoint btnPoint = [sender convertPoint:CGPointZero toView:_collectionView]; NSIndexPath *indexPath = [_collectionView indexPathForItemAtPoint:btnPoint]; if (nil != indexPath) { //按钮点击处理 } }
5.等比例缩放图片及问题
这是通过一个不大于1的缩放系数来实现，写在UIImage的category中。
+(UIImage *)scaleImage:(UIImage *)image toScale:(float)scaleSize;先看普通的
+(UIImage *)scaleImage:(UIImage *)image toScale:(float)scaleSize{ UIGraphicsBeginImageContext(CGSizeMake(image.size.width * scaleSize, image.size.height * scaleSize)); [image drawInRect:CGRectMake(0, 0, image.size.width * scaleSize, image.size.height * scaleSize)]; UIImage *scaledImage = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); return scaledImage; }但这样会出现失真问题，图片会变得模糊。应用下边的
+(UIImage *)scaleImage:(UIImage *)image toScale:(float)scaleSize{ CGSize newSize = CGSizeMake(image.size.width * scaleSize, image.size.height * scaleSize); UIGraphicsBeginImageContextWithOptions(newSize, NO, 0.0); [image drawInRect:CGRectMake(0, 0, newSize.width, newSize.height)]; UIImage* scaledImage = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext(); return scaledImage; }
6.app版本号比较
由于一般的版本号格式都是类似于“3.1.1”这样的，所以不能用floatValue比较。这时可以用
NSString *num1 = @"5.2.0"; NSString *num2 = @"5.3.0"; if ([num1 compare:num2 options:NSNumericSearch] == NSOrderedDescending) { NSLog(@"%@ is bigger",num1); } else { NSLog(@"%@ is bigger",num2); }其中NSOrderedDescending是降序排列
###更新---补充版本号相等的情况###上述写法有缺陷，当版本号相同时也会提示，应该添加相同情形时才完整
if ([num1 compare:num2 options:NSNumericSearch] == NSOrderedDescending) { NSLog(@"%@ is bigger",num1); } else if([num1 isEqualToString:num2]){ NSLog(@"same"); } else { NSLog(@"%@ is bigger",num2); }
转载于:https://www.cnblogs.com/Apologize/p/6306634.html
