How to use the default iOS7 UIAnimation curve

问题:

iOS7 animations don't behave the same way as in iOS6. They appear to use a different bezier curve. Where iOS6 uses a kind of "easeInOutSine" curve, iOS7 is more of the "easeInOutExpo" kind. (http://matthewlein.com/ceaser/)

Is there a way to use that curve? I want to sync my animations when the keyboard opens/closes.

回答1:

Here's how I do it (at least when the keyboard is about to be shown)

- (void)keyboardWillShow:(NSNotification *)notification {
    NSDictionary *keyboardAnimationDetail = [notification userInfo];
    UIViewAnimationCurve animationCurve = [keyboardAnimationDetail[UIKeyboardAnimationCurveUserInfoKey] integerValue];
    CGFloat duration = [keyboardAnimationDetail[UIKeyboardAnimationDurationUserInfoKey] floatValue];

    [UIView animateWithDuration:duration delay:0.0 options:(animationCurve << 16) animations:^{
        // Set the new properties to be animated here
    } completion:nil];
}

You get the animation curve from the keyboard notification as usual and translate it to an animation option by bit-shifting it.

回答2:

Update, fixed in 7.1. No longer necessary.

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For whatever reason, the animation curve reported on keyboard dismissal is incorrect. It seems to actually be 6 << 16 instead of 7 << 17.

Here's what I do with UIKeyboardWillChangeFrameNotification to determine which animation curve to use.

NSDictionary *keyboardAnimationDetail = [notification userInfo];

CGRect keyboardEndFrameWindow = [keyboardAnimationDetail[UIKeyboardFrameEndUserInfoKey] CGRectValue];

double keyboardTransitionDuration  = [keyboardAnimationDetail[UIKeyboardAnimationDurationUserInfoKey] doubleValue];

// gives incorrect value of 7 on dismissal
// UIViewAnimationCurve keyboardTransitionAnimationCurve  = [keyboardAnimationDetail[UIKeyboardAnimationCurveUserInfoKey] integerValue];

CGRect keyboardEndFrameView = [self.view convertRect:keyboardEndFrameWindow fromView:nil];

CGFloat newConstant = (self.view.frame.size.height - keyboardEndFrameView.origin.y);

[UIView animateWithDuration:keyboardTransitionDuration
                      delay:0.0f
                    options:newConstant == 0 ? (6 << 16) : (7 << 16)
                 animations:^{
                     self.tableView.contentInset = UIEdgeInsetsMake(self.tableView.contentInset.top, 0, self.view.frame.size.height - keyboardEndFrameView.origin.y + self.commentToolbar.frame.size.height, 0);
                     self.tableView.scrollIndicatorInsets = UIEdgeInsetsMake(self.tableView.scrollIndicatorInsets.top, 0, self.view.frame.size.height - keyboardEndFrameView.origin.y + self.commentToolbar.frame.size.height, 0);
                     self.commentViewToSuperviewBottomConstraint.constant = (self.view.frame.size.height - keyboardEndFrameView.origin.y);
                     [self.view layoutIfNeeded];
                 }
                 completion:^(__unused BOOL finished){
                 }];

Basically I determine if the keyboard frame is hiding by seeing if the new y origin will be just outside our view's frame (newConstant). Then based on that I use either 6 or 7:

newConstant == 0 ? (6 << 16) : (7 << 16)

The rest is just adjusting my tableView contentInset and scrollIndicatorInsets, as well as changing the constant on the toolbar that is moving with the keyboard.