how to limit the position of a UIImageView inside a boundary range?

I got an Icon of UIImageView named IconView. I want to make sure when I touch and move this Icon, its position only change inside the boundary of another UIImageView named backgroundView.

I thought after I add the IconView as the s开发者_运维知识库ubview of backgroundView, the boundary is automatically set. But it seems to be wrong.

[backgroundView addSubview:IconView];

after this, I can still move the Icon to the outside of backgroundView. how can I set the limitation? thanks.

You try like this,

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
    UITouch *touch = [[event allTouches] anyObject];

    CGPoint location = [touch locationInView:self.view];


    if(CGRectContainsPoint(urBoundryBackgroundImage.frame, location)) {
         //do your moving stuff            
    }
}