Undo and redo tool for Android

Apryse supports undo/redo for any manipulation of the document.

For convenience, we have provided a class called UndoRedoManager to facilitate undo/redo. This class is attached by default to the ToolManager class. In other words, if you are using ToolManger you don't need to do anything to make undo/redo work. Just ensure you raise the appropriate events existing in ToolManager when you manipulate the document:

To do undo/redo operation simply call

String undoInfo = mToolManager.getUndoRedoManger().undo();

or

String redoInfo = mToolManager.getUndoRedoManger().redo();

The undoInfo/redoInfo contains the information about the action that has been undone/redone; for example, it can be something like this when the undo/redo action is corresponding to annotation addition:

{"Action":"Add Text Box","Annot Info":"{\"Page Numbers\":\"1 \",\"Rects\":\"197 511 307 534 \"}"}

From this you can understand the action was adding a text box in page 1 at the rectangle (197 511 307 534). This information can be used later, for example, in jumping to the last modification which will be explained in the next section.

If you are in the PDF view and like the view to jump to the undo/redo changes you can call

UndoRedoManager.jumpToUndoRedo(PDFViewCtrl, String, boolean)

This function will show the transition with an animation. The second input argument is the attached information to undo action, and the third argument specifies if the action was undo or redo.

There area several facility functions provided in UndoRedoManger to see the action you can undo/redo, including

The information attached to the undo/redo action can be used to determine the type of action:

If you don't use ToolManger or you'd like to have your own undo/redo control you can use undo/redo APIs in PDFViewCtrl to achieve this.

You need to enable undo/redo in PDFViewCtrl as the first step:

mPdfViewCtrl.enableUndoRedo();

You can see if the undo/redo is enabled in the PDFViewCtrl using:

boolean isUndoRedoEnabled = mPdfViewCtrl.isUndoRedoEnabled();

After enabling undo/redo, you should determine the snapshots for undo/redo operations. This is done by calling the following when, or shortly after, a modification on the document occurs:

try {
    mPdfViewCtrl.takeUndoSnapshot(info);
} catch (Exception e) {
    e.printStackTrace();
}

If you have at least one undo snapshot you can back out the last modification using undo() and get the information you passed through when taking the undo snapshot:

try {
    mPdfViewCtrl.cancelRendering();
    info = mPdfViewCtrl.undo();
} catch (Exception e) {
    e.printStackTrace();
}

Or, if you have any undo in the stack you can redo the last undo by

try {
    mPdfViewCtrl.cancelRendering();
    info = mPdfViewCtrl.redo();
} catch (Exception e) {
    e.printStackTrace();
}