How to resize UIView by dragging from its edges?

Question

In my iPad app, I want the users to be able to resize a UIView by dragging the view from its edges. I\'ll be using iOS 5 SDK, so what\'s the cleanest approach t

Answer 1

You can do this by checking the touch-start point. If it hits one of your four corners you can resize based on the distance between that touch-start point and the current-touch point. (If the touch-start point didn't hit a corner, we just move the view instead of resizing.)

Define the size of your draggable corners.

CGFloat kResizeThumbSize = 45.0f;

Add these instance variables to your class to keep track of touch state and which way we're resizing.

@interface MY_CLASS_NAME : UIView {
    BOOL isResizingLR;
    BOOL isResizingUL;
    BOOL isResizingUR;
    BOOL isResizingLL;
    CGPoint touchStart;
}

Handle the touch start / change events.

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    UITouch *touch = [[event allTouches] anyObject];
    touchStart = [[touches anyObject] locationInView:self];
    isResizingLR = (self.bounds.size.width - touchStart.x < kResizeThumbSize && self.bounds.size.height - touchStart.y < kResizeThumbSize);
    isResizingUL = (touchStart.x