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This new shift behavior mode enables the flexible header to mimic the behavior of UINavigationController's setNavigationBarHidden:. When the shift behavior is set to this new value, the flexible header can be hidden or shown using the shiftHeaderOnScreenAnimated: and shiftHeaderOffScreenAnimated: APIs, but user interactions will not affect the header's visibility. Added an example to the configurator to demonstrate the behavior. Part of https://github.com/material-components/material-components-ios/issues/5185
2.9 KiB
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;
}
If you would like to be able to show and hide your flexible header similar to how UINavigationBar
allows the navigation bar to be shown and hidden, you can use the hideable shift behavior. This
behavior will allow you to toggle visibility of the header using the shiftHeaderOffScreenAnimated:
and shiftHeaderOnScreenAnimated: APIs only; the user will not be able to drag the header either on
or off-screen.
Swift
headerViewController.headerView.shiftBehavior = .hideable
// You can now toggle visibility of the header view using the following invocations:
headerViewController.headerView.shiftHeaderOffScreen(animated: true)
headerViewController.headerView.shiftHeaderOnScreen(animated: true)
override func childViewControllerForStatusBarHidden() -> UIViewController? {
return headerViewController
}
Objective-C
headerViewController.headerView.shiftBehavior = MDCFlexibleHeaderShiftBehaviorHideable;
// You can now toggle visibility of the header view using the following invocations:
[headerViewController.headerView shiftHeaderOffScreenAnimated:YES];
[headerViewController.headerView shiftHeaderOnScreenAnimated:YES];
- (UIViewController *)childViewControllerForStatusBarHidden {
return _headerViewController;
}