Markdown support in Android TextView
There's no built-in support for Markdown in the Android SDK. You'll have to use a lib like markdown4j or CommonMark.
There is no inherit support for markdown in textview, however if you only need simple markdown-lite implementation via simple "regexp" matching, this section from my "load readme from project root folder" in https://github.com/mofosyne/instantReadmeApp would help.
Note that this does not remove the markup in the text, only styles the lines differently. This may be a good or bad thing, depending on your application.
Oh and the nice thing? It styles in native textview, so the text is still selectable like normal text.
Specifically this line: https://github.com/mofosyne/instantReadmeApp/blob/master/app/src/main/java/com/github/mofosyne/instantreadme/ReadMe.java#L137
Slightly modified below: private void updateMainDisplay(String text) to private void style_psudomarkdown_TextView(String text, TextView textview_input), so you could use the same function for different textviews
```
/*
Text Styler
A crappy psudo markdown styler. Could do with a total revamp.
*/
/*
* Styling the textview for easier readability
* */
private void style_psudomarkdown_TextView(String text, TextView textview_input) {
//TextView mTextView = (TextView) findViewById(R.id.readme_info);
TextView mTextView = textview_input;
// Let's update the main display
// Needs to set as spannable otherwise http://stackoverflow.com/questions/16340681/fatal-exception-string-cant-be-cast-to-spannable
mTextView.setText(text, TextView.BufferType.SPANNABLE);
// Let's prettify it!
changeLineinView_TITLESTYLE(mTextView, "# ", 0xfff4585d, 2f); // Primary Header
changeLineinView(mTextView, "\n# ", 0xFFF4A158, 1.5f); // Secondary Header
changeLineinView(mTextView, "\n## ", 0xFFF4A158, 1.2f); // Secondary Header
changeLineinView(mTextView, "\n---", 0xFFF4A158, 1.2f); // Horizontal Rule
changeLineinView(mTextView, "\n>", 0xFF89e24d, 0.9f); // Block Quotes
changeLineinView(mTextView, "\n - ", 0xFFA74DE3, 1f); // Classic Markdown List
changeLineinView(mTextView, "\n- ", 0xFFA74DE3, 1f); // NonStandard List
//spanSetterInView(String startTarget, String endTarget, int typefaceStyle, String fontFamily,TextView tv, int colour, float size)
// Limitation of spanSetterInView. Well its not a regular expression... so can't exactly have * list, and *bold* at the same time.
spanSetterInView(mTextView, "\n```\n", "\n```\n", Typeface.BOLD, "monospace", 0xFF45c152, 0.8f, false); // fenced code Blocks ( endAtLineBreak=false since this is a multiline block operator)
spanSetterInView(mTextView, " **" , "** ", Typeface.BOLD, "", 0xFF89e24d, 1f, true); // Bolding
spanSetterInView(mTextView, " *" , "* ", Typeface.ITALIC, "", 0xFF4dd8e2, 1f, true); // Italic
spanSetterInView(mTextView, " ***" , "*** ", Typeface.BOLD_ITALIC, "", 0xFF4de25c, 1f, true); // Bold and Italic
spanSetterInView(mTextView, " `" , "` ", Typeface.BOLD, "monospace", 0xFF45c152, 0.8f, true); // inline code
spanSetterInView(mTextView, "\n " , "\n", Typeface.BOLD, "monospace", 0xFF45c152, 0.7f, true); // classic indented code
}
private void changeLineinView(TextView tv, String target, int colour, float size) {
String vString = (String) tv.getText().toString();
int startSpan = 0, endSpan = 0;
//Spannable spanRange = new SpannableString(vString);
Spannable spanRange = (Spannable) tv.getText();
while (true) {
startSpan = vString.indexOf(target, endSpan-1); // (!@#$%) I want to check a character behind in case it is a newline
endSpan = vString.indexOf("\n", startSpan+1); // But at the same time, I do not want to read the point found by startSpan. This is since startSpan may point to a initial newline.
ForegroundColorSpan foreColour = new ForegroundColorSpan(colour);
// Need a NEW span object every loop, else it just moves the span
// Fix: -1 in startSpan or endSpan, indicates that the indexOf has already searched the entire string with not valid match (Lack of endspan check, occoured because of the inclusion of endTarget, which added extra complications)
if ( (startSpan < 0) || ( endSpan < 0 ) ) break;// Need a NEW span object every loop, else it just moves the span
// Need to make sure that start range is always smaller than end range. (Solved! Refer to few lines above with (!@#$%) )
if (endSpan > startSpan) {
//endSpan = startSpan + target.length();
spanRange.setSpan(foreColour, startSpan, endSpan, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
// Also wannna bold the span too
spanRange.setSpan(new RelativeSizeSpan(size), startSpan, endSpan, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
spanRange.setSpan(new StyleSpan(Typeface.BOLD), startSpan, endSpan, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
}
}
tv.setText(spanRange);
}
private void changeLineinView_TITLESTYLE(TextView tv, String target, int colour, float size) {
String vString = (String) tv.getText().toString();
int startSpan = 0, endSpan = 0;
//Spannable spanRange = new SpannableString(vString);
Spannable spanRange = (Spannable) tv.getText();
/*
* Had to do this, since there is something wrong with this overlapping the "##" detection routine
* Plus you only really need one title.
*/
//while (true) {
startSpan = vString.substring(0,target.length()).indexOf(target, endSpan-1); //substring(target.length()) since we only want the first line
endSpan = vString.indexOf("\n", startSpan+1);
ForegroundColorSpan foreColour = new ForegroundColorSpan(colour);
// Need a NEW span object every loop, else it just moves the span
/*
if (startSpan < 0)
break;
*/
if ( !(startSpan < 0) ) { // hacky I know, but its to cater to the case where there is no header text
// Need to make sure that start range is always smaller than end range.
if (endSpan > startSpan) {
//endSpan = startSpan + target.length();
spanRange.setSpan(foreColour, startSpan, endSpan, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
// Also wannna bold the span too
spanRange.setSpan(new RelativeSizeSpan(size), startSpan, endSpan, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
spanRange.setSpan(new StyleSpan(Typeface.BOLD_ITALIC), startSpan, endSpan, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
}
}
//}
tv.setText(spanRange);
}
private void spanSetterInView(TextView tv, String startTarget, String endTarget, int typefaceStyle, String fontFamily, int colour, float size, boolean endAtLineBreak) {
String vString = (String) tv.getText().toString();
int startSpan = 0, endSpan = 0;
//Spannable spanRange = new SpannableString(vString);
Spannable spanRange = (Spannable) tv.getText();
while (true) {
startSpan = vString.indexOf(startTarget, endSpan-1); // (!@#$%) I want to check a character behind in case it is a newline
endSpan = vString.indexOf(endTarget, startSpan+1+startTarget.length()); // But at the same time, I do not want to read the point found by startSpan. This is since startSpan may point to a initial newline. We also need to avoid the first patten matching a token from the second pattern.
// Since this is pretty powerful, we really want to avoid overmatching it, and limit any problems to a single line. Especially if people forget to type in the closing symbol (e.g. * in bold)
if (endAtLineBreak){
int endSpan_linebreak = vString.indexOf("\n", startSpan+1+startTarget.length());
if ( endSpan_linebreak < endSpan ) { endSpan = endSpan_linebreak; }
}
// Fix: -1 in startSpan or endSpan, indicates that the indexOf has already searched the entire string with not valid match (Lack of endspan check, occoured because of the inclusion of endTarget, which added extra complications)
if ( (startSpan < 0) || ( endSpan < 0 ) ) break;// Need a NEW span object every loop, else it just moves the span
// We want to also include the end "** " characters
endSpan += endTarget.length();
// If all is well, we shall set the styles and etc...
if (endSpan > startSpan) {// Need to make sure that start range is always smaller than end range. (Solved! Refer to few lines above with (!@#$%) )
spanRange.setSpan(new ForegroundColorSpan(colour), startSpan, endSpan, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
spanRange.setSpan(new RelativeSizeSpan(size), startSpan, endSpan, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
spanRange.setSpan(new StyleSpan(typefaceStyle), startSpan, endSpan, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
// Default to normal font family if settings is empty
if( !fontFamily.equals("") ) spanRange.setSpan(new TypefaceSpan(fontFamily), startSpan, endSpan, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
}
}
tv.setText(spanRange);
}
```
The above implementation supports only up to 2 headers (but you can easily modify the regexp to support more than 2 level headers).
It is a series of regexp based text view consisting of two functions for regexp that matches always a line changeLineinView() and changeLineinView_TITLESTYLE()
For multiline spanning spanSetterInView() function deals with it.
So extending it to fit your purpose as long as you have a regexp that doesn't clash with any other syntax would be possible.
Markdownish Syntax:
This is the supported syntax. Can't support full markdown, since this is only a lite hacky implementation. But kind handy for a no frills display that is easy to type on a mobile phone keypad.
# H1 only in first line (Due to technical hacks used)
## H2 headers as usual
## Styling
Like: *italic* **bold** ***bold_italic***
## Classic List
- list item 1
- list item 2
## Nonstandard List Syntax
- list item 1
- list item 2
## Block Quotes
> Quoted stuff
## codes
here is inline `literal` codes. Must have space around it.
```
codeblocks
Good for ascii art
```
Or 4 space code indent like classic markdown.