PageStorageKey<T> class

A ValueKey that defines where PageStorage values will be saved.

Scrollables (ScrollPositions really) use PageStorage to save their scroll offset. Each time a scroll completes, the scrollable's page storage is updated.

PageStorage is used to save and restore values that can outlive the widget. The values are stored in a per-route Map whose keys are defined by the PageStorageKeys for the widget and its ancestors. To make it possible for a saved value to be found when a widget is recreated, the key's values must not be objects whose identity will change each time the widget is created.

For example, to ensure that the scroll offsets for the scrollable within each MyScrollableTabView below are restored when the TabBarView is recreated, we've specified PageStorageKeys whose values are the tabs' string labels.

new TabBarView(
  children: myTabs.map((Tab tab) {
    new MyScrollableTabView(
      key: new PageStorageKey<String>(tab.text), // like 'Tab 1'
      tab: tab,
   ),
 }),
)
Inheritance

Constructors

PageStorageKey(T value)
Creates a ValueKey that defines where PageStorage values will be saved.
const

Properties

hashCode int
The hash code for this object. [...]
read-only, inherited
runtimeType Type
A representation of the runtime type of the object.
read-only, inherited
value → T
The value to which this key delegates its operator==
final, inherited

Methods

noSuchMethod(Invocation invocation) → dynamic
Invoked when a non-existent method or property is accessed. [...]
inherited
toString() String
Returns a string representation of this object.
inherited

Operators

operator ==(dynamic other) bool
The equality operator. [...]
inherited