The aim for this library is to render markdown as first class citizen on Android - Spannables. It has reasonable defaults to display markdown, but also gives ability to customize almost every detail for your liking.

The most basic example would be:

Markwon.setMarkdown(textView, "**Hello *there*!!**")

Please note, that this library depends on commonmark-java (and some extensions):

compile 'com.atlassian.commonmark:commonmark:0.9.0'
compile 'com.atlassian.commonmark:commonmark-ext-gfm-strikethrough:0.9.0'
compile 'com.atlassian.commonmark:commonmark-ext-gfm-tables:0.9.0'

Configuration

In order to render correctly markdown, this library need a SpannableConfiguration instance. It has 2 factory methods:

// creates default instance
SpannableConfiguration.create(Context);

// returns configurable Builder
SpannableConfiguration.builder(Context);

SpannableConfiguration.Builder class has these configurable properties (which are described in more detail further):

public Builder theme(SpannableTheme theme);
public Builder asyncDrawableLoader(AsyncDrawable.Loader asyncDrawableLoader);
public Builder syntaxHighlight(SyntaxHighlight syntaxHighlight);
public Builder linkResolver(LinkSpan.Resolver linkResolver);
public Builder urlProcessor(UrlProcessor urlProcessor);
public Builder htmlParser(SpannableHtmlParser htmlParser);

// and obviously:
public SpannableConfiguration build();

Theme

SpannableTheme controlls the appearance of rendered markdown. It has pretty reasonable defaults, which are established based on style of a TextView to which it is applied. It has some factory methods:

// creates ready-to-use SpannableThemeObject
SpannableTheme.create(Context);

// can be used to tweak default appearance
SpannableTheme.builderWithDefaults(Context);

// returns empty builder (no default values are set)
SpannableTheme.builder();

// returns a builder that is instantiated with all values from specified SpannableTheme
SpannableTheme.builder(SpannableTheme copyFrom);

SpannableTheme.Builder have these configurations:

Link

public Builder linkColor(@ColorInt int linkColor);

Block

// left margin for: lists & quotes (text is shifted)
public Builder blockMargin(@Dimension int blockMargin);

Quote

// width of quote indication (the `|`)
public Builder blockQuoteWidth(@Dimension int blockQuoteWidth);

// color of `|` quote indication
public Builder blockQuoteColor(@ColorInt int blockQuoteColor);

Lists

// color of list item bullets(●, ○, ■)/numbers
public Builder listItemColor(@ColorInt int listItemColor);

// stroke width for list bullet (2nd level - `○`)
public Builder bulletListItemStrokeWidth(@Dimension int bulletListItemStrokeWidth);

// width of list bullet (●, ○, ■)
public Builder bulletWidth(@Dimension int bulletWidth);

Code

// text color for `code` blocks
public Builder codeTextColor(@ColorInt int codeTextColor);

// background color for `code` blocks
public Builder codeBackgroundColor(@ColorInt int codeBackgroundColor);

// left margin for multiline `code` blocks
public Builder codeMultilineMargin(@Dimension int codeMultilineMargin);

// typeface of `code` block
public Builder codeTypeface(@NonNull Typeface codeTypeface);

// text size for `code` block
public Builder codeTextSize(@Dimension int codeTextSize);

Headings

// height of the `break` line under h1 & h2
public Builder headingBreakHeight(@Dimension int headingBreakHeight);

// color of the `break` line under h1 & h2
public Builder headingBreakColor(@ColorInt int headingBreakColor);

SuperScript & SupScript

// ratio for <sup> & <sub> text size (calculated based on TextView text size)
public Builder scriptTextSizeRatio(@FloatRange(from = .0F, to = Float.MAX_VALUE) float scriptTextSizeRatio);

Thematic break

// the `---` thematic break color
public Builder thematicBreakColor(@ColorInt int thematicBreakColor);

// the `---` thematic break height
public Builder thematicBreakHeight(@Dimension int thematicBreakHeight);

Tables

// padding inside a table cell
public Builder tableCellPadding(@Dimension int tableCellPadding);

// color of table borders
public Builder tableBorderColor(@ColorInt int tableBorderColor);

// the `stroke` width of table border
public Builder tableBorderWidth(@Dimension int tableBorderWidth);

// the background of odd table rows
public Builder tableOddRowBackgroundColor(@ColorInt int tableOddRowBackgroundColor);

Images

By default this library does not render any of the images. It's done to simplify rendering of text-based markdown. But if images must be supported, then the AsyncDrawable.Loader can be specified whilst building a SpannableConfiguration instance:

final AsyncDrawable.Loader loader = new AsyncDrawable.Loader() {
    @Override
    public void load(@NonNull String destination, @NonNull final AsyncDrawable drawable) {
        // `download` method is here for demonstration purposes, it's not included in this interface
        download(destination, new Callback() {
            @Override
            public void onDownloaded(Drawable d) {
                // additionally we can call `drawable.isAttached()`
                // to ensure if AsyncDrawable is in layout
                drawable.setResult(d);
            }
        });
    }

    @Override
    public void cancel(@NonNull String destination) {
        // cancel download here
    }
};

// `this` here referrs to a Context instance
final SpannableConfiguration configuration = SpannableConfiguration.builder(this)
        .asyncDrawableLoader(loader)
        .build();

There is also standalone artifact that supports image loading out-of-box (including support for SVG & GIF), but provides little to none configuration and could be somewhat not optimal. Please refer to the README of the module.

Tables

Tables are supported but with some limitations. First of all: table will always take the full width of the TextView Canvas. Second: each column will have the same width (we do not calculate the weight of column) - so, a column width will be: totalWidth / columnsNumber.

Syntax highlight

This library does not provide ready-to-be-used implementation of syntax highlight, but it can be added via SyntaxHighlight interface whilst building SpannableConfiguration:

final SyntaxHighlight syntaxHighlight = new SyntaxHighlight() {
    @NonNull
    @Override
    public CharSequence highlight(@Nullable String info, @NonNull String code) {
        // create Spanned of highlight here
        return null; // must not return `null` here
    }
};

final SpannableConfiguration configuration = SpannableConfiguration.builder(this)
        .syntaxHighlight(syntaxHighlight)
        .build();

Url processing

If you wish to process urls (links & images) that markdown contains, the UrlProcessor can be used:

final UrlProcessor urlProcessor = new UrlProcessor() {
    @NonNull
    @Override
    public String process(@NonNull String destination) {
        // modify the `destination` or return as-is
        return null;
    }
};

final SpannableConfiguration configuration = SpannableConfiguration.builder(this)
        .urlProcessor(urlProcessor)
        .build();

The primary goal of additing this abstraction is to give ability to convert relative urls to absolute ones. If it fits your purpose, then UrlProcessorRelativeToAbsolute can be used:

final UrlProcessor urlProcessor = new UrlProcessorRelativeToAbsolute("https://this-is-base.org");

Link resolver

Link resolver is used to navigate to clicked link. By default LinkResolverDef is used and it just constructs an Intent and launches activity that can handle it, or silently fails if activity cannot be resolved. The main interface:

public interface Resolver {
    void resolve(View view, @NonNull String link);
}

HTML parser

As markdown supports HTML to be inlined, we need to introduce another entity that does (limited) parsing. Obtain an instance of SpannableHtmlParser via one of these factory methods:

SpannableHtmlParser.create(SpannableTheme, AsyncDrawable.Loader)
SpannableHtmlParser.create(SpannableTheme, AsyncDrawable.Loader, UrlProcessor, LinkSpan.Resolver)