Undo
Helper class that encapsulates all undo/redo functionality for toolbars. This class handles undo/redo menu item creation, async button state updates, and undo/redo action execution.
This helper implements ANR prevention patterns to avoid blocking on Pdfium mutexes:
UndoProvider.canUndo and UndoProvider.canRedo are called on a background thread with a 500ms timeout fallback
UndoProvider.undo and UndoProvider.redo are executed on a background thread to prevent main thread blocking
Constructors
Types
Interface that must be implemented by toolbars using this helper.
Functions
Creates the undo/redo menu items for the toolbar. Returns a list of menu items to be added to the toolbar.
Binds a custom undo/redo provider. Must be called when the toolbar's controller is bound. Use this for non-UndoManager providers (e.g., DocumentEditorUndoProvider). Note: Manual calls to updateUndoRedoButtons are required when the undo/redo state changes.
Binds the undo manager from the given fragment. Must be called when the toolbar's controller is bound. Creates a UndoManagerUndoProvider wrapper automatically.
Executes a redo action on a background thread to prevent ANRs from Pdfium mutex blocking. The button enabled state should already ensure this is only called when redo is available and no other undo/redo operation is currently executing. This method is thread-safe and can be called from any thread.
Executes an undo action on a background thread to prevent ANRs from Pdfium mutex blocking. The button enabled state should already ensure this is only called when undo is available and no other undo/redo operation is currently executing. This method is thread-safe and can be called from any thread.
Unbinds the provider and cancels any pending state updates or executions. Must be called when the toolbar's controller is unbound.
Updates the enabled state of undo/redo buttons asynchronously. Calls UndoProvider.canUndo and UndoProvider.canRedo on a background thread with a 500ms timeout fallback to prevent ANRs.