UIView is the parent class for display objects on the iPhone (unless you're using Core Animation or OpenGL). Buttons, text fields, and images are all children of UIView.
A view can contain other views. If it does, it is said to be the superview to the contained views, which are called subviews. To add a subview to an existing UIView:
To remove a subview from its superview:
To adjust the size or position of a view, see View Frames and Bounds.
In iOS 4 and later, you can use animation blocks to animate the above properties. (Older versions of iOS used beginAnimation/commitAnimations.) There are three block-based animation methods you can use:
If you want to run another animation (or trigger some action) after the first animation finishes, use animateWithDuration:animations:completion:
To specify animation options (such as the animation curve), or delay the start of animation, use animateWithDuration:delay:options:animations:completion:
Animation options allow you to specify the type of animation, repeat/autoreverse options, and whether to allow user interaction while the view is animating. To specify multiple options:
This example rotates the view by 45 degrees, then rotates it back on completion:
See the UIView Class Methods documentation for more info on the various animation methods.
A view can contain other views. If it does, it is said to be the superview to the contained views, which are called subviews. To add a subview to an existing UIView:
[viewObj addSubview:otherViewObj];
[otherViewObj removeFromSuperview];
Animating Views
A view's size, location, rotation or transparency can be animated using several UIView class methods. You can animate the following view properties:| frame | Moves or resizes the view within its superview |
| center | Moves the view within its superview |
| bounds | Changes the view's bounding box |
| transform | Rotate, scale, translate, or skew the view |
| alpha | Adjusts the view's transparency (alpha) level, from 0.0 (transparent) to 1.0 (opaque) |
animateWithDuration:animations:animateWithDuration:animations:completion:
animateWithDuration:delay:options:animations:completion:
Here's a simple example. This moves a view to a new location:animateWithDuration:delay:options:animations:completion:
CGRect newFrame = theView.frame; newFrame.origin.x += 500; // shift right by 500pts [UIView animateWithDuration:1.0 animations:^{ theView.frame = newFrame; }];
[UIView animateWithDuration:1.0 animations:^{ theView.frame = newFrame; // move } completion:^(BOOL finished){ // code to run when animation completes // (in this case, another animation:) [UIView animateWithDuration:1.0 animations:^{ theView.alpha = 0.0; // fade out } completion:^(BOOL finished){ [theView removeFromSuperview]; }]; }];
[UIView animateWithDuration:1.0 delay: 0.5 options: UIViewAnimationOptionCurveEaseIn animations:^{ theView.frame = newFrame; // move } completion:nil]; // no completion handler
options: UIViewAnimationOptionCurveLinear | UIViewAnimationOptionAllowUserInteraction;
Rotation
To rotate a view, apply a CGAffineTransformMakeRotation result to the view's .transform property:float degrees = 45.0; float radians = (degrees/180.0) * M_PI; [UIView animateWithDuration:0.25 animations:^{ theView.transform = CGAffineTransformMakeRotation(radians); }];
Undoing Rotations
To restore a view to its original angle, set its transform property to CGAffineTransformIdentity.theView.transform = CGAffineTransformIdentity;
float degrees = 45.0; float radians = (degrees/180.0) * M_PI; [UIView animateWithDuration:0.25 animations:^{ theView.transform = CGAffineTransformMakeRotation(radians); } completion:^(BOOL finished){ [UIView animateWithDuration:0.25 animations:^{ theView.transform = CGAffineTransformIdentity; }]; }];
