UIButton causing a crash - ios

Question

I'm having a bit of a problem here. I've created a button and want it to change it's backgroundImage on being clicked. It's not working and I get a SIGABRT error.
The code is as follows:
- (IBAction)indicatedButton:(id)sender
{
if ([sender isSelected])
{
[sender setBackgroundImage:[UIImage imageNamed:#"completeTickBox.png"]];
}
else
{
[sender setBackgroundImage:[UIImage imageNamed:#"blankTickBox.png"]];
}
}

Answer 1

I think you want:
[sender setBackgroundImage:[UIImage ....] forState:UIControlStateNormal];
Here's the relevant Apple documentation on the method: https://developer.apple.com/library/ios/documentation/uikit/reference/UIButton_Class/UIButton/UIButton.html#//apple_ref/occ/instm/UIButton/setBackgroundImage:forState:
So in your case, it would be:
- (IBAction)indicatedButton:(id)sender
{
if ([sender isSelected])
{
[sender setBackgroundImage:[UIImage imageNamed:#"completeTickBox.png"] forState:UIControlStateNormal];
}
else
{
[sender setBackgroundImage:[UIImage imageNamed:#"blankTickBox.png"] forState:UIControlStateNormal];
}
}
Assuming here that "sender" is actually a UIButton.

Answer 2

First verify you're getting a UIButton
-(IBAction indicatedButton:(id)sender
{
if ([sender isKindOfClass:[UIButton class]])
{
}
}
Convention tip: best practice for properties of an object is to use dot notation (isSelected is a BOOL property of UIButton)
-(IBAction indicatedButton:(id)sender
{
if ([sender isKindOfClass:[UIButton class]])
{
if (sender.isSelected)
{
}
}
}
If you're just using a regular button, but what you want is a "toggle" button (it's one image, or a different image), then you need to set the selected state property for the button, so that it -knows- it's selected after it's been touched (and vice versa if it isn't)
-(IBAction indicatedButton:(id)sender
{
if ([sender isKindOfClass:[UIButton class]])
{
if (sender.isSelected)
{
[sender setSelected:NO]; // if we were selected, we won't be now
UIImage *buttonImage = [UIImage imageNamed:#"completeTickBox.png"];
[sender setImage:buttonImage forState:UIControlStateNormal];
}
else if (!sender.isSelected)
{
[sender setSelected:YES]; // if we aren't selected, we will be now
UIImage *buttonImage = [UIImage imageNamed:#"blankTickBox.png"];
[sender setImage:buttonImage forState:UIControlStateNormal];
}
}
}
Instead of using introspection (the checking class types), if you know you want to work with a button, you could also change the button sender type from id to UIButton. You can do this without rewiring the button to the storyboard/nib
-(IBAction indicatedButton:(UIButton *)sender
{
if (sender.isSelected)
{
[sender setSelected:NO]; // if we were selected, we won't be now
UIImage *buttonImage = [UIImage imageNamed:#"completeTickBox.png"];
[sender setImage:buttonImage forState:UIControlStateNormal];
}
else if (!sender.isSelected)
{
[sender setSelected:YES]; // if we aren't selected, we will be now
UIImage *buttonImage = [UIImage imageNamed:#"blankTickBox.png"];
[sender setImage:buttonImage forState:UIControlStateNormal];
}
}

Answer 3

you have to cast sender as UIButton because sender is (id) and the object you want is UIButton so
put this line in your codeUIButton *btn=sender;
- (IBAction)indicatedButton:(id)sender
{
UIButton *btn= sender;
if ([btn isSelected])
{
[btn setBackgroundImage:[UIImage imageNamed:#"completeTickBox.png"] forState:UIControlStateNormal];
}
else
{
[btn setBackgroundImage:[UIImage imageNamed:#"blankTickBox.png"] forState:UIControlStateNormal];
}
}