Android Syntax Highlighting?

Question

Does anyone know of syntax highlighting libraries which work on Android? I've looked at jsyntaxpane but that doesn't seem to support Android.

Answer 1

I managed to create a syntax highlighter for Android, based on the Prettify. It was easy, actually, when I found the Java Prettify. Just download it (sadly, it is not published for maven) and add its jar to the build path of you application.

The syntax highlighter I created based on it:

public class PrettifyHighlighter {
    private static final Map<String, String> COLORS = buildColorsMap();

    private static final String FONT_PATTERN = "<font color=\"#%s\">%s</font>";

    private final Parser parser = new PrettifyParser();

    public String highlight(String fileExtension, String sourceCode) {
        StringBuilder highlighted = new StringBuilder();
        List<ParseResult> results = parser.parse(fileExtension, sourceCode);
        for(ParseResult result : results){
            String type = result.getStyleKeys().get(0);
            String content = sourceCode.substring(result.getOffset(), result.getOffset() + result.getLength());
            highlighted.append(String.format(FONT_PATTERN, getColor(type), content));
        }
        return highlighted.toString();
    }

    private String getColor(String type){
        return COLORS.containsKey(type) ? COLORS.get(type) : COLORS.get("pln");
    }

    private static Map<String, String> buildColorsMap() {
        Map<String, String> map = new HashMap<>();
        map.put("typ", "87cefa");
        map.put("kwd", "00ff00");
        map.put("lit", "ffff00");
        map.put("com", "999999");
        map.put("str", "ff4500");
        map.put("pun", "eeeeee");
        map.put("pln", "ffffff");
        return map;
    }
}

The colors of the syntax are hardcoded, but may be also set by i.e. application preferences. In order to display a Java source code in a TextView, just do:

// code is a String with source code to highlight
// myTextView is a TextView component
PrettifyHighlighter highlighter = new PrettifyHighlighter();
String highlighted = highlighter.highlight("java", code);
myTextView.setText(Html.fromHtml(highlighted));

The Java Prettify library made my application around 50kB bigger.

Answer 2

Well, I did a open-source syntax-highlighting editor for Android:

https://github.com/markusfisch/ShaderEditor

It's quite simple and maybe only suitable for small data, but it's probably a good starting point.

Answer 3

For read-only syntax highlighting, you have two options:

1. Find a Java library that can syntax highlight and generate HTML using <font color=""> (i.e., no CSS). You can then use Html.fromHtml() to create a Spanned object which you can hand to a TextView.

2. Find a Java library that can syntax highlight and generate any sort of HTML. You can then display that in a WebView. This appears to be what the android-codepad project a commenter linked to does.

If you are seeking syntax highlighting for an editor, that is significantly more difficult. While EditText can take the same Spanned that TextView can, you would have to run everything through the syntax highlighter to reflect changes, either on a per-keystroke basis, or after a pause in typing. Or, you would need to bake the syntax highlighting rules much more tightly to the editing process, so you can somehow incrementally adjust the highlighting without having to redo the entire contents of the EditText. I have not seen an open source syntax-highlighting editor for Android -- a few closed-source ones as apps on the Play Store, though.

Answer 4

Hi you can use my CodeEditor

Simply use:

Setup build.gradle (project)

allprojects {
    repositories {
        ...
        maven {
            url 'https://jitpack.io'
        }
    }
}

build.gradle (app)

dependencies {
    ...
    compile 'com.github.ahmadaghazadeh:CodeEditor:1.0.15'
}

XML DataBinding <com.github.ahmadaghazadeh.editor.widget.CodeEditor bind:code="@{viewModel.code}" bind:lang="@{viewModel.lang}" android:layout_width="match_parent" android:layout_height="match_parent"/>

XML

    <com.github.ahmadaghazadeh.editor.widget.CodeEditor
        bind:code="<html></html>"
        bind:lang="html"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

Answer 5

I have created an API for text highlighting which can solve your problem.

https://github.com/nakshay/TextHighlighter

This API allows you to pass words and colours specific to words and will return the string which is formatted with html tags which you can send to Html.fromHtml() to get highlighted text. add below Gradle dependency to your module's gradle file.

compile 'com.github.akshay-naik:texthighlighterapi:1.1.0'

Answer 6

920 Text Editor (app on Play Store, source on GitHub) uses a combination of WebView and Ace, an embeddable code editor written in JavaScript.

I'm working on an app which is an IDE for Android, I think I'm going the same way.

Answer 7

If you prefer you can create your own syntax highlight using the Highlight library.

The lib works through schemes, which are basically a combination of a rule (with regex) and a related modification. There are some ready-made, like ColorScheme, SyleScheme, OnClickScheme etc., but you can implement the Scheme interface and create your own.

The base class of the lib is Highlight, where spans are processed. You can use it directly, like in the example below where we highlight some key words of the Java language from TextView

//create Highlight
Highlight highlight = new Highlight();

//scheme color example
highlight.addScheme(
        new ColorScheme(
                Pattern.compile("\\b(private)|(public)|(protected)|(void)\\b"),
                Color.parseColor("#CC7832")
        )
);

//...

//textview example
highlight.setSpan(binding.toolbarTitle);

But to create a syntax highlight more is needed than that, and for that there is the HighlightTextWatcher class, optimized for large texts with processing by altered lines of the LinesTextWatcher class (which you can extend). See an example of using this class.

//create TextWatcher
HighlightTextWatcher highlightTextWatcher = new HighlightTextWatcher();

//scheme color example
highlightTextWatcher.addScheme(
        new ColorScheme(
                Pattern.compile("\\b(private)|(public)|(protected)|(void)\\b"),
                Color.parseColor("#CC7832")
        )
);

//...

//edittext example
binding.edittext.addTextChangedListener(highlightTextWatcher);

You can add as many schemes as you like and the lib does the rest.

implementation 'com.github.Irineu333:Highlight:1.0.1' (jitpack)