Ios – How to prevent manual zooming in a UIScrollView

cocoa-touchiosuiscrollview

Hopefully someone can help with this issue. I have a class derived from UIScrollView and I'd like to prevent the user from being able to zoom or scroll via manual pinch and swipe gestures. All view navigation will instead be controlled by programmatic means in response to where a user taps (think of an ebook reader where tapping on the left or right sides of the display causes the view to scroll by exactly one page width). Any suggestions on how to implement this?

Best Answer

On your - (void)viewDidLoad; you should be able to just disable whatever gesture recognizer you want. In this case:

UIPinchGestureRecognizer *pinchRecognizer = self.pinchGestureRecognizer;
pinchRecognizer.enabled = NO;

UIPanGestureRecognizer *panRecognizer = self.scrollView.panGestureRecognizer;
panRecognizer.enabled = NO;

I sometimes do this from view controllers that contain UIScrollViews. I just target the scroll view (self.scrollView.pinchGestureRecognizer) and temporarily disable gestures when the app. is in a certain state.

Related Solutions

Ios – How to disable the UITableView selection

All you have to do is set the selection style on the UITableViewCell instance using either:

Objective-C:

cell.selectionStyle = UITableViewCellSelectionStyleNone;

[cell setSelectionStyle:UITableViewCellSelectionStyleNone];

Swift 2:

cell.selectionStyle = UITableViewCellSelectionStyle.None

Swift 3 and 4.x:

cell.selectionStyle = .none

Further, make sure you either don't implement -tableView:didSelectRowAtIndexPath: in your table view delegate or explicitly exclude the cells you want to have no action if you do implement it.

More info here and here

Ios – How to sort an NSMutableArray with custom objects in it

Compare method

Either you implement a compare-method for your object:

- (NSComparisonResult)compare:(Person *)otherObject {
    return [self.birthDate compare:otherObject.birthDate];
}

NSArray *sortedArray = [drinkDetails sortedArrayUsingSelector:@selector(compare:)];

NSSortDescriptor (better)

or usually even better:

NSSortDescriptor *sortDescriptor;
sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"birthDate"
                                           ascending:YES];
NSArray *sortedArray = [drinkDetails sortedArrayUsingDescriptors:@[sortDescriptor]];

You can easily sort by multiple keys by adding more than one to the array. Using custom comparator-methods is possible as well. Have a look at the documentation.

Blocks (shiny!)

There's also the possibility of sorting with a block since Mac OS X 10.6 and iOS 4:

NSArray *sortedArray;
sortedArray = [drinkDetails sortedArrayUsingComparator:^NSComparisonResult(Person *a, Person *b) {
    return [a.birthDate compare:b.birthDate];
}];

Performance

The -compare: and block-based methods will be quite a bit faster, in general, than using NSSortDescriptor as the latter relies on KVC. The primary advantage of the NSSortDescriptor method is that it provides a way to define your sort order using data, rather than code, which makes it easy to e.g. set things up so users can sort an NSTableView by clicking on the header row.