material-components_material-components-ios/components/FlexibleHeader/docs/shift-behavior.md

Shifting a flexible header off-screen

A flexible header that tracks a scroll view will expand and contract its height in reaction to scroll view events. A flexible header can also shift off-screen in reaction to scroll view events by changing the flexible header's behavior.

Swift

headerViewController.headerView.shiftBehavior = .enabled

Objective-C

headerViewController.headerView.shiftBehavior = MDCFlexibleHeaderShiftBehaviorEnabled;

Important: when a flexible header shifts off-screen it will not hide the content views. Your content views are responsible for hiding themselves in reaction to the flexible header shifting off-screen. Read the section on Reacting to frame changes for more information.

It is also possible to hide the status bar when shifting the flexible header off-screen. Enable this behavior by setting the enabledWithStatusBar behavior and implementing childViewControllerForStatusBarHidden on the parent view controller.

Swift

headerViewController.headerView.shiftBehavior = .enabledWithStatusBar

override func childViewControllerForStatusBarHidden() -> UIViewController? {
  return headerViewController
}

Objective-C

headerViewController.headerView.shiftBehavior = MDCFlexibleHeaderShiftBehaviorEnabledWithStatusBar;

- (UIViewController *)childViewControllerForStatusBarHidden {
  return _headerViewController;
}