Implementing a rich text editor in Android?
I am wondering if there are any good options to implement a rich text editor in Android. Please note I am talking about a rich text editor that can be used in an Android application, not the one embedded in a web page using HTML and Javascript.
My requirements are:
- Basic formatting (color, fonts, highlight, bold, italic, underline, etc.)
- Hyperlinks
- Inline images
- Bullet lists and numbered lists
- Inline table (only the contents inside a cell is editable, not the table structure)
As you can see, this is pretty much something quite similar to a typical RichEdit control on Windows.
Here are some efforts (investigation & prototyping) I have made so far:
Using WebView
I have tried using a WebView control to load an HTML fragment with one . The content becomes editable and as it is HTML, I suppose it can meet most of my requirements. But it has several issues:
- (deadly) No text caret. The user will have no idea where his/her typed characters will be inserted.
- The on-screen soft keyboard is not visible by default. There is a trick that the user has to long-press the Menu button to bring up the keyboard. But I think this is a very bad user experience. Besides, the screen layout is not properly rearranged and the text inserting point sometimes will be covered by the keyboard.
Using EditText
I have tried using the EditText control. It seems to support some level of rich text editing (color, fonts, bold, italic, underline, inline images, bullet lists). But I still cannot figure out how I can implement the following requirements:
- Control the appereance of the bullet symbol (dot, circle, dash, arrow, star, etc.)
- Numbered list (1., 2., 3., etc.)
- Table
BTW, I have seen there are several *Span classes out there but I am not sure if they can be any help... And the http://developer.android.com does not provide much useful information about them.
So, how on earth can I implement a rich text editor on Android? Can I extends the EditText and add my new functionalities? Or should I do something from scratch - extends the View and implement everything by myself? For later option (extending View), I actually even don't know how to show a text caret and blink it, not mentionging moving the caret with user typing.
I am desperate now... Any hints?
Thanks!
-Tony
(EDIT)
After some further investigation, it looks like extending EditText would be my best bet. I somehow figured out how to use those Span classes and guess I should be able to do most of the tricks by using (extending) them.
For example, extending the BulletSpan and overriding drawLeadingMargin should give me the control of the bullet appereances. Extending the LeadingMarginSpan should help me on the numbered list.
As to the table, my initial plan is to extend the LineBackgroundSpan and draw all the table borders in the drawBackground override. However, I still need to figure out how to layout all the text in the table cells and properly handle the caret movement and selection. Suggestions?
Answer
I just published my rich text editor component under the Apache 2.0 license:
https://github.com/1gravity/Android-RTEditor
