RunDo

RunDo allows developers to add Undo/Redo functionality to editable text fields in Android.

This library aims to counteract some of the performance problems that can occur when working with large text blocks in Android in the following ways:

• Text is only saved to memory when the user stops typing. The bulk of code is only run when required, rather than updating with every key stroke.
• Only text that has changed between saves is committed to memory, rather than saving all text present in the widget.
• Only short, altered sections of text are inserted whenever an undo() or redo() method is called, and text fields are updated intelligently based on whether old text is to be added to, deleted from or replaced. This can drastically increase performance on older hardware, as calling setText() with large volumes of text can cause UI freezes.

ChangeLog

View Changelog

Current version is v0.2

Implementation

Gradle Dependency

jcenter()

Add the following to your module's build.gradle file:

dependencies {
    compile 'com.werdpressed.partisan:rundo:0.2'
}

maven

If you experience issues, add the following in addition to the dependency above:

repositories {
    maven {
        url 'https://dl.bintray.com/ppartisan/maven/'
    }
}

Instantiation

As the class extends android.app.Fragment, it requires FragmentManager

RunDoMixer mRunDoMixer;
//...
mRunDoMixer = (RunDoMixer) getFragmentManager().findFragmentByTag(RunDoMixer.RUNDO_MIXER_TAG);

if (mRunDoMixer == null) {
   testEditText = (EditText) findViewById(R.id.test_edit_text);
   mRunDoMixer = RunDoMixer.newInstance(testEditText.getId(), 0, 0);
   getFragmentManager()
       .beginTransaction()
       .add(mRunDoMixer, RunDoMixer.RUNDO_MIXER_TAG)
       .commit();
}

Note: Since v0.2, newInstance(int editTextResourceId) can be used as shorthand for newInstance(editTextResourceId, 0, 0), to use default countdown and arraySize values.

The newInstance() method takes three paramters, all int values. The first is the id of either an EditText object, or the id of an object of a class that inherits from EditText. It is possible to pass 0 and later assign something suitable with setEditText(Object object).

The other two parameters are optional. The first sets the countdown timer, in milliseconds, and determines how long the system will wait from the last keypress before saving any altered text to the Undo queue. A value of less than one will revert to the default value of two seconds. The final parameter specifies the maximum size of the Undo and Redo queues before old entries are deleted. The default size is ten.

Calling Undo/Redo

To call Undo or Redo, use the undo() and redo() methods on the RunDoMixer object:

mRunDoMixer.undo();
mRunDoMixer.redo();

For example:

@Override
public void onClick(View v) {
    int id = v.getId();
    switch (id) {
        case R.id.undo_button:
            mRunDoMixer.undo();
            break;
        case R.id.redo_button:
            mRunDoMixer.redo();
            break;
    }

}

Visual Feedback

A Toast notification will appear to let the user know that they have reached the end of the Undo/Redo queue. This will either occur if they are at one extreme end of a full queue, or if the next entry is null.

To deactivate this feature, or change the message, use setUndoQueueEmptyMessage(boolean condition, String message) and setRedoQueueEmptyMessage(coolean condition, String message). Setting condition to false will deactivate these notifications entirely, whilst any non-null text in the second argument will override the default message.

Hardware Keyboard Shortcuts

By default, the follwing shortcuts are ennabled for hardware keyboard users:

• Ctrl + Z for Undo
• Ctrl + Y for Redo

Deactivate with setKeyboardShortcuts(false).

Clearing Queues

To clear all Undo and Redo queues, use clearAllQueues()

Callbacks

To receive a callback whenever undo() or redo() is called, have your class implement RunDoMixer.UndoRedoCallbacks. This will provide the following methods:

@Override
public void undoCalled() {
}

@Override
public void redoCalled() {
}

Other Extras...

RunDo relies heavily on a custom String comparison class called SubtractStrings. SubtractStrings compares two String objects, and returns data regarding:

• The points where the two strings first and last deviate from each other.
• The subString from both the old text and new text, if one replaced a section of text in the other.
• Options to return values in respect to the larger of the two strings, or in respect to the "new" text in relation to the "old" text.

This class may be useful in its own right for some projects.