快速更改图像不起作用

Question

EDIT: After changing the image to a label and transform a string ">" 90 degrees it is still not working correctly. I print out the values of the degrees and it works as expected but the transform is not happening.

I have a totally strange behaviour in my iOS App. I have a table view with section headers. In these section headers are typical dropdown images. One arrow down and one arrow up image. When I tap on the header section the cells display or hide dynamically. Now I want to change the image also according to that.

This is the code that runs when I tap the section header:

func selectedSection(sender: UIButton) {
    let previousSelected = self.selectedSection
    self.selectedSection = sender.tag

    if previousSelected != self.selectedSection {
        // one section opens another gets closed
        // workaround so the animation does not look awful for section headers
        print("Previous: \(previousSelected)")
        sectionHeaders[previousSelected].toggleIcon()
        print("Selected: \(self.selectedSection)")
        sectionHeaders[self.selectedSection].toggleIcon()
        print("***********")

        var indexPathToInsert = [IndexPath]()
        var indexPathToDelete = [IndexPath]()

        for i in 0..<self.menuItems[self.selectedSection].getSubItems().count {
            indexPathToInsert.append(IndexPath(row: i, section: self.selectedSection))
        }

        for i in 0..<self.menuItems[previousSelected].getSubItems().count {
            indexPathToDelete.append(IndexPath(row: i, section: previousSelected))
        }


        tableView.beginUpdates()
        tableView.deleteRows(at: indexPathToDelete, with: .none)
        tableView.insertRows(at: indexPathToInsert, with: .automatic)
        tableView.endUpdates()
    } else {
        // close the section so the selected section is 0 again
        self.selectedSection = 0

        print("Previous: \(previousSelected)")
        sectionHeaders[previousSelected].toggleIcon()
        print("***********")
        tableView.reloadSections([previousSelected], with: .none)
    }
}

Toggle Icon looks like this:

func toggleIcon() {
    isOpen = !isOpen
    print("\(isOpen)")

    if isOpen {
        print("Works")
        self.sectionIcon.image = UIImage(named: "arrow-up")
    } else {
        print("Does not work")
        self.sectionIcon.image = UIImage(named: "arrow-down")
    }
}

When I run this and click on different headers everything works as expected. But as soon as I close one section without opening another this section is broken. The code still works but it does not change the image. It prints out:

'Selected: 1'
true
Works

And when I use a breakpoint the code is called where it sets the icon to arrow-up. However, it does not change the image.

I really don't understand what is happening. Is it not allowed to change an image more than once?

Thanks for your help!

Answer 1

I'm not sure if this is what cause the issue, but keep in mind that ALL UI Changes has be on the main thread.

on Swift 3,

try wrapping your call to update the image with something like

DispatchQueue.main.async { }

Good luck :)

Answer 2

Ok I was able to solve it with my own implementation.

I changed the else statement in selectedSection(sender: UIButton) to:

// close the section so the selected section is 0 again
        self.selectedSection = 0

        print("Previous: \(previousSelected)")
        sectionHeaders[previousSelected].toggleIcon()
        print("***********")

        var indexPathToDelete = [IndexPath]()
        for i in 0..<self.menuItems[previousSelected].getSubItems().count {
            indexPathToDelete.append(IndexPath(row: i, section: previousSelected))
        }

        tableView.beginUpdates()
        tableView.deleteRows(at: indexPathToDelete, with: .left)
        tableView.endUpdates()

So animating the whole section did not work. Thanks @Mitesh jadav for his option but this does not close the other open sections so I sticked with my solution.