CWAC RichEditText: Letting Users Make Text Pretty

Android's EditText widget supports formatted (a.k.a., "rich text") editing. It just lacks any way for the user to supply formatting, and it does not provide much in the way of convenience methods for a developer to, say, tie in some sort of toolbar to allow users to format selections.

That's where RichEditText comes in.

RichEditText is a drop-in replacement for EditText that:

• Provides an action mode on Android 4.0+ that allows users to format selected pieces of text
• Provides convenience methods to allow developers to trigger formatting for selected text via other means

This widget is packaged as an Android Studio library module, with a demo/ subdirectory containing a regular Android Studio app module with a couple of activities demonstrating the use of RichEditText.

This library also contains a series of utility classes for working with rich text. In particular, it has code to convert a Spanned to and from XHTML, as an alternative to the toHtml() and fromHtml() methods on Android's Html class.

In addition to the documentation on this page, partial JavaDocs are also available for the editor widget and the utility classes.

This Android library project is available as an artifact for use with Gradle. To use that, add the following blocks to your build.gradle file:

repositories {
    maven {
        url "https://repo.commonsware.com.s3.amazonaws.com"
    }
}

dependencies {
    compile 'com.commonsware.cwac:richedit:0.5.+'
}

Or, if you cannot use SSL, use http://repo.commonsware.com for the repository URL.

If you are not using Gradle, download or clone this repo, and add the richedit/ module to your Android Studio project as a library module.

NOTE: This project is no longer compatible with Eclipse at the source level, as of version 0.5.0. A ZIP file containing what should be an Eclipse-compatible project is in the releases area. However, this ZIP file has not been tested — please file bug reports if you encounter problems with it.

NOTE: If you were using v0.2.0 with ActionBarSherlock, ActionBarSherlock support was removed from this project as of v0.3.0. Please remain on v0.2.0, or switch to the native API Level 11+ action bar (a.k.a., "15 is the new 10").

Usage: RichEditText

Simply add com.commonsware.cwac.richedit.RichEditText widgets to your layout as needed:

<?xml version="1.0" encoding="utf-8"?>
<com.commonsware.cwac.richedit.RichEditText xmlns:android="http://schemas.android.com/apk/res/android"
  android:id="@+id/editor"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"
  android:gravity="top|left"
  android:inputType="textMultiLine">

  <requestFocus/>

</com.commonsware.cwac.richedit.RichEditText>

At this time, there are no custom attributes used by RichEditText.

On its own, by default, RichEditText provides one means of users applying formatting: the standard <Ctrl>-<B> for bold, <Ctrl>-<I> for italics, and <Ctrl>-<U> for underline work if there is a selection. You can disable this by calling setKeyboardShortcutsEnabled(false).

If you want an on-screen UI for formatting, you have two choices.

First, you can call enableActionModes() on the RichEditText. This will add a "FORMAT" entry on the action mode that comes up when the user highlights some prose in the editor. Tapping that will allow the user to toggle various effects.

The action modes work so-so on phones at this time — tablets work better. To get it to work on phones at all, you will need to include android:imeOptions="flagNoExtractUi" as an attribute on the RichEditText.

NOTE: The action modes do not work on Android 5.1. They will be deprecated in an upcoming release of this library and will be removed entirely before the library reaches 1.0. A stock toolbar implementation will be provided instead as the out-of-the-box way to offer users the ability to control effects.

Alternatively, you can have your own toolbar or gesture interface or whatever to allow users to format text. In that case, here are the two key methods to call on RichEditText:

• applyEffect() changes the current selection, applying or removing an effect (e.g., making the selection bold). The first parameter is the effect to apply (e.g., RichEditText.BOLD). The second parameter is the new value for the effect. Many effects take boolean values, so applyEffect(RichEditText.BOLD, true) would format the current selection as bold.

• setOnSelectionChangedListener() is where you register a RichEditText.OnSelectionChangedListener object, which will be called with onSelectionChanged() whenever the user changes the selection in the widget (i.e., highlights text or taps to un-select the highlight). You are provided the start and end positions of the selection (as were supplied to onSelectionChanged() to RichEditText itself by Android), plus a list of effects that are active on that selection. This will allow you to update your toolbar to indicate what is and is not in use, and so you know what to do when the user taps on one of those toolbar buttons again.

Supported Effects

At the time of this writing, here are the RichEditText static data members for each supported effect:

• BOLD
• ITALIC
• UNDERLINE
• STRIKETHROUGH
• SUPERSCRIPT
• SUBSCRIPT
• TYPEFACE
• ABSOLUTE_SIZE
• RELATIVE_SIZE
• URL
• BACKGROUND (color)
• FOREGROUND (color)

There are other effects presently implemented, but they will be revised shortly, including name and data type changes, so don't mess with them yet.

To use the BACKGROUND and FOREGROUND effects, you will need to call setColorPicker() on the RichEditText widget, supplying an implementation of the ColorPicker interface. That has one required method: pick(). It receives a ColorPickerOperation, on which you can call hasColor() (returns true if we are editing an existing color) and getColor() (returns the existing color value, if applicable). Your job is to collect a color from the user, then call either onColorPicked() (supplying the color) or onPickerDismissed() (indicating that the user abandoned the request for a color and that the selection should remain unchanged). See the demo app for an example implementation.

Known Limitations: RichEditText

• This widget has not been tested with the AppCompat action bar backport. Most likely, it will not work well. AppCompat support is planned, at least to get a Toolbar implementation going. Tint support will be added as well, if and only if the process for doing so is documented.

• The demo app uses a ColorMixerActivity from the CWAC-ColorMixer library for its implementation of ColorPicker. While easy to integrate, this approach has one major flaw: the color picker remains in the foreground after a configuration change. Since the demo activity is recreated, so its its RichEditText widget, and any existing selection (or ColorPickerOperation) is lost. What the demo app should do is dismiss the color picker on a configuration change, since the chosen color will not be applied anyway.

Usage: XHTML Conversion

The principal set of utilities for this library is to convert Spanned objects to/from XHTML.

Scope of Support

The primary objective of this conversion logic is to support the formatting offered by the RichEditText widget. Apps that wish to allow users to enter in rich text can use RichEditText, then persist the Spanned using this library. Later on, if the user wants to edit rich text entered previously, the app can convert the XHTML back into a Spanned to supply to RichEditText.

A secondary objective is to allow the resulting persisted value to be usable by anything that needs an XHTML representation of rich text. For example, you might supply the XHTML to a Web service, or upload it to a Web site. That's why XHTML is chosen as the representation format, as opposed to some sort of Serializable or other binary packaging.

Whereas Html.fromHtml() is designed to parse semi-arbitrary HTML, this library is not. You are welcome to feed it XHTML from wherever and see if it works. As the saying goes, YMMV.

Basic Parsing and Generating

Given a Spanned (e.g., getText() on a RichEditText), to get an XHTML representation of the Spanned, create an instance of SpannedXhtmlGenerator and call toXhtml() on it. This will return a String of XHTML.

Later on, to get the Spanned back from that XHTML, create an instance of a SpannableStringGenerator and call fromXhtml() on it, passing it the String of XHTML, and getting back a a Spannable that you can use with RichEditText or whatever.

And that's pretty much it.

Conversion Rules

A stock set of rules, embodied in a collection of SpanTagHandler instances, are applied to convert the Spanned to XHTML and back again:

CharacterStyle	XHTML Tag Structure
AbsoluteSizeSpan	<span style="font-size:...px;">
BackgroundColorSpan	<span style="background-color:#...">
BulletSpan	<li> inside of a <ul>
ForegroundColorSpan	<font color="...">
LineAlignmentSpan	<div style="text-align:..."> or <ul style="text-align:...">
RelativeSizeSpan	<span style="font-size:...%;">
StrikethroughSpan	<strike>
StyleSpan	<b> or <i>
SubscriptSpan	<sub>
SuperscriptSpan	<sup>
TypefaceSpan	<span style="font-family:...;">
UnderlineSpan	<u>
URLSpan	<a href="...">

Customizing the Conversion

If there are new CharacterStyle subclasses that you want to support, and you want to do so on a global (process-level) basis, create a subclass of SpanTagHandler and register it via registerGlobalSpanTagHandler() on the SpanTagHandler class.

If you want to override the default rules, create a subclass (or subclasses) of SpanTagHandler for those rules. Then, create an instance of SpanTagRoster and register your handlers via registerSpanTagHandler() on the roster. You can pass in your roster to the constructor of SpannedXhtmlGenerator or SpannableStringGenerator.

There are a bunch of implemenations of SpanTagHandler, for the stock rules, in the com.commonsware.cwac.richtextutils.handler package, so you can see what creating these looks like. There is also a ClassSpanTagHandler that you can use to use a <span class="..."> tag for a particular CharacterStyle, if you want to use CSS classes for the actual formatting rules.

Note, though, that if you customize the rules by any of these mechanisms, it is incumbent upon you to keep those customizations. If you generate XHTML using one set of rules, you need to use the same (or a compatible) set of rules to restore the Spanned.

Known Limitations

• Two start tags in sequence may be flipped in order during conversion. So, for example, suppose you had <b><i>Foo</i></b>, and you converted that into a Spanned, then back into XHTML. The resulting XHTML could be the same or could be <i><b>Foo</b></i>.

• It is possible that multiple <span> elements will be applied for the same text (e.g., it is adjusted using a RelativeSizeSpan and a BackgroundColorSpan). No attempt is made to coalesce those <span> elements into one, even though from an XHTML standpoint, this is certainly possible (and perhaps even desired).

• The XHTML generated by this library is unofficial until the library reaches 1.0. At that point, the XHTML specification will remain fixed through point-level releases (e.g., 1.1) until the next major release (e.g., 2.0). Hence, until the library reaches 1.0, and for major releases after that, you may need to go through some cleanup logic, as your XHTML may not be parsed the same way as it had been in earlier versions of the library.

Dependencies

There are no third-party dependencies at this time for the library. The demo app depends not only on this library but also on the CWAC-ColorMixer library.

This project should work on API Level 11 and higher, except for any portions that may be noted otherwise in this document. Please report bugs if you find features that do not work on API Level 11 and are not noted as requiring a higher version.

Version

This is version v0.5.1 of this module, meaning it is creeping towards respectability.

Demo

In the demo/ module you will find a sample activity that demonstrates the use of RichEditText. In the demo-utils/ module you will find a sample activity that demonstrates the use of the the XHTML utilties.

Also, the androidTest/ directory in the main/ sourceset of the richedit/ module contains a number of instrumentation tests.

License

The code in this project is licensed under the Apache Software License 2.0, per the terms of the included LICENSE file.

Questions

If you have questions regarding the use of this code, please post a question on StackOverflow tagged with commonsware-cwac and android after searching to see if there already is an answer. Be sure to indicate what CWAC module you are having issues with, and be sure to include source code and stack traces if you are encountering crashes.

If you have encountered what is clearly a bug, or if you have a feature request, please post an issue. Be certain to include complete steps for reproducing the issue.

Do not ask for help via Twitter.

Also, if you plan on hacking on the code with an eye for contributing something back, please open an issue that we can use for discussing implementation details. Just lobbing a pull request over the fence may work, but it may not.

Release Notes

• v0.5.1: fixed issue 15 and issue 17
• v0.5.0: added preliminary support for bullets, added XHTML conversion classes
• v0.4.0: added support for size, color, and URL effects
• v0.3.1: updated for Android Studio 1.0 and new AAR publishing system
• v0.3.0: removed ActionBarSherlock support, icon for FORMAT action mode item, fixed clipboard bug, added Gradle support
• v0.2.0: added keyboard shortcuts for bold/italic/underline and test suite, bug fixes
• v0.1.1: added disableActionModes() and fixed bug related to conditional action mode usage
• v0.1: added action mode support using ActionBarSherlock for pre-Honeycomb devices
• v0.0.3: removed RichEditor, replaced it with custom action modes
• v0.0.2: added RichEditor and made various fixes
• v0.0.1: initial release

Who Made This?