iOS工作笔记(十六)

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);    
}