How to perform Redo Undo operation in EditText

Question

I want to know is there any method or any link or tutorial to perform redo undo operation in Android edittext. If any one knows than please let me know.

Answer 1

Quick note on the Antti-Brax/Divers(Kidinov) solution. It works great, except if you try to use it with a TextView post-API 23, you'll run into problems, because guess-what, Google actually added a hidden UndoManager (android.content.UndoManager) and didn't document it or make it obvious it was there. But if you have a hard/bluetooth keyboard in Marshmallow or Nougat and hit ^Z or SHIFT-^Z, you'll get undo/redo.

The problem comes if you're already using Antti-Brax's class with an EditText, and you also hook it to ^Z and shift-^Z, you'll run into problems with anyone using a hard keyboard. Namely the ^Z will trigger BOTH the native and Antti-Brax's undo, leading to two undos simultaneously, which isn't good. And after a few of them, you'll probably get a Spannable out of bounds crash.

A possible solution I found is to subclass the TextView/TextEdit/whatever and intercept the undo/redo calls from the TextView so they don't run as follows:

    @Override
    public boolean onTextContextMenuItem(int id) {
        int ID_UNDO, ID_REDO;

        try {
            ID_UNDO = android.R.id.undo;
            ID_REDO = android.R.id.redo;
        } catch (Resources.NotFoundException e) {
            ID_UNDO = 16908338; // 0x1020032
            ID_REDO = 16908339; // 0x1020033
        }
        return !((id == ID_UNDO) || (id == ID_REDO)) && super.onTextContextMenuItem(id);
    }

Those magic id numbers were found here, and are used only as a backup if the android.R.id.undo values aren't found. (it also might be reasonable to assume that if the values aren't there the feature isn't there, but anyway...)

This is not the best solution because both undo trackers are still there and both are running in the background. But at least you won't trigger both of them simultaneously with ^Z. It's the best I could think to do until this gets officially documented and the getUndoManager() methods of TextView is no longer hidden...

Why they made a feature you can't turn off (or even know if it was there or not) "live" in released Android I can't say.

I just opened an issue on Android's issue tracker if anyone wants to follow this.