Image for UIControlState.Selected does not appear

Question

The title says it all. Here is my code:

func createCheckBoxButton(xPos: CGFloat, yPos: CGFloat, tag: Int) -> UIButton {
    var checkBox = UIButton(frame: CGRect(x: xPos, y: yPos, width: checkBoxSize, height: checkBoxSize))
    checkBox.setBackgroundImage(UIImage(named: "checkbox_inactive"), forState: UIControlState.Normal)
    checkBox.setBackgroundImage(UIImage(named: "checkbox_pressed"), forState: UIControlState.Highlighted)
    checkBox.setBackgroundImage(UIImage(named: "checkbox_active"), forState: UIControlState.Selected)
    checkBox.tag = tag
    checkBox.contentMode = .ScaleAspectFit
    checkBox.addTarget(self, action: "processButton:", forControlEvents: UIControlEvents.TouchUpInside)
    return checkBox
}

And there is the called function when my button is pressed:

func processButton(sender: UIButton) {
    if (answerViewArray[sender.tag].backgroundColor == UIColor.whiteColor()) {
        answerViewArray[sender.tag].backgroundColor = myColor.pinky()
    } else {
        answerViewArray[sender.tag].backgroundColor = UIColor.whiteColor()
    }
    let tag = answerButtonsArray[sender.tag]
    answer.buttonPressed(tag)
}

When I launch the app, the checkbox_inactive image is there. When I press and keep it pressed, the checkbox_pressed image appears. But when I release my click the checkbox_inactive appears again instead of checkbox_active.

I also tried with an UIImageView, which would be the best solution for me actually. I set my checkbox as an UIImageView and at the top of my general view I put an invisible view so I can click everywhere. But when I press my invisible view, the UIImageView simply disappears.

Here is the code:

func createCheckBoxButton(xPos: CGFloat, yPos: CGFloat) -> UIImageView {
    var checkBox = UIImageView(frame: CGRect(x: xPos, y: yPos, width: checkBoxSize, height: checkBoxSize))
    checkBox.image = UIImage(named: "checkbox_inactive")
    checkBox.contentMode = .ScaleAspectFit
    return checkBox
}

Here is the function called:

func processButton(sender: UIButton) {
    if (answerViewArray[sender.tag].backgroundColor == UIColor.whiteColor()) {
        answerViewArray[sender.tag].backgroundColor = myColor.pinky()
        checkBoxArray[sender.tag].image = UIImage(named: "checkbox-active")
    } else {
        answerViewArray[sender.tag].backgroundColor = UIColor.whiteColor()
        checkBoxArray[sender.tag].image = UIImage(named: "checkbox-inactive")
    }

    let tag = answerButtonsArray[sender.tag]

    answer.buttonPressed(tag)
}

Answer 1

To make appear checkbox_active when you release your button you should make selected=true for the pressed button.

So your function should be like:

func processButton(sender: UIButton) {
  // If button not selected
  if(sender.selected==false){
    sender.selected = true;
  }
  else{ // If button already selected
    sender.selected = false;
  }

  // Do your other stuff
}