flutter_widget_from_html 0.17.1

Flutter package to render html as widgets that supports hyperlink, image, audio, video, iframe and many other tags.

Flutter Widget from HTML

Flutter package to render html as widgets that supports hyperlink, image, audio, video, iframe and 70+ other tags.

Live demo

This package supports most common HTML tags for easy usage. If you don't want to include all of its dependencies in your build, it's possible to use flutter_widget_from_html_core with a subset of the mixins to control your app size:

• fwfh_cached_network_image for optimized image rendering
• fwfh_chewie for VIDEO support
• fwfh_just_audio for AUDIO support
• fwfh_svg for SVG support
• fwfh_url_launcher to launch URLs
• fwfh_webview for IFRAME support

Getting Started

Add this to your app's pubspec.yaml file:

dependencies:
  flutter_widget_from_html: ^0.17.0

Platform specific configuration

iOS

This package uses just_audio to play audio and this dependency uses a microphone API. By default, the App Store requires a usage description which can be skipped by editing your ios/Podfile. See the detailed instruction on its pub.dev page.

If you don't need AUDIO tag support (e.g. your HTML never has that tag), it may be better to switch to the core package and use it with a subset of the mixins. See Extensibility for more details.

Usage

Then you have to import the package with:

import 'package:flutter_widget_from_html/flutter_widget_from_html.dart';

And use HtmlWidget where appropriate:

HtmlWidget(
  // the first parameter (`html`) is required
  '''
  <h3>Heading</h3>
  <p>
    A paragraph with <strong>strong</strong>, <em>emphasized</em>
    and <span style="color: red">colored</span> text.
  </p>
  ''',

  // all other parameters are optional, a few notable params:

  // specify custom styling for an element
  // see supported inline styling below
  customStylesBuilder: (element) {
    if (element.classes.contains('foo')) {
      return {'color': 'red'};
    }

    return null;
  },

  customWidgetBuilder: (element) {
    if (element.attributes['foo'] == 'bar') {
      // render a custom block widget that takes the full width
      return FooBarWidget();
    }

    if (element.attributes['fizz'] == 'buzz') {
      // render a custom widget inline with surrounding text
      return InlineCustomWidget(
        child: FizzBuzzWidget(),
      );
    }

    return null;
  },

  // this callback will be triggered when user taps a link
  // return true to indicate the tap has been handled
  onTapUrl: (url) {
    debugPrint('tapped $url');
    return true;
  },

  // this callback will be triggered when user taps an image
  onTapImage: (image) {
    debugPrint('image tapped: \'${image.sources.first.url}\'');
  },

  // select the render mode for HTML body
  // by default, a simple `Column` is rendered
  // consider using `ListView` or `SliverList` for better performance
  renderMode: RenderMode.column,

  // set the default styling for text
  textStyle: TextStyle(fontSize: 14),
),

Callbacks

• onTapUrl: return true to indicate the URL tap was handled; when not handled and the URL is an in-page anchor (e.g. #id or ${baseUrl}#id), it scrolls to the anchor automatically.
• onTapImage: receives ImageMetadata; access the first source via image.sources.first.url.
• onLoadingBuilder: shown while the widget/image is loading; receives loadingProgress (0.0–1.0 or null).
• onErrorBuilder: shown when a complex element fails to render; receives the thrown error.

Features

HTML tags

Below tags are the ones that have special meaning / styling, all other tags will be parsed as text. Compare between Flutter rendering and browser's.

• A: underline, theme accent color
  • Scroll to anchor
  • Launch URL via url_launcher with base URL resolver
• AUDIO via just_audio
• H1/H2/H3/H4/H5/H6
• IFRAME via webview_flutter
• IMG with support for asset (asset://), data uri, local file (file://) and network image via cached_network_image. Additional .svg file support via flutter_svg.
• LI/OL/UL with support for:
  • Attributes: type, start, reversed
  • Inline style list-style-type values: lower-alpha, upper-alpha, lower-latin, upper-latin, circle, decimal, disc, lower-roman, upper-roman, square
• TABLE/CAPTION/THEAD/TBODY/TFOOT/TR/TD/TH with support for:
  • TABLE attributes border, cellpadding, cellspacing
  • TD/TH attributes colspan, rowspan, valign
  • Table is scrollable if columns are too wide
• SVG via flutter_svg
• VIDEO via chewie
• ABBR, ACRONYM, ADDRESS, ARTICLE, ASIDE, B, BIG, BLOCKQUOTE, BR, CENTER, CITE, CODE, DD, DEL, DETAILS, DFN, DIV, DL, DT, EM, FIGCAPTION, FIGURE, FONT, FOOTER, HEADER, HR, I, INS, KBD, MAIN, MARK, NAV, NOSCRIPT, P, PRE, Q, RP, RT, RUBY, S, SAMP, SECTION, SMALL, STRIKE, STRONG, STYLE, SUB, SUMMARY, SUP, TT, U, VAR
• Everything with screenshot: https://demo.fwfh.dev/supported/tags.html
• Try with fwfh.dev

These tags and their contents will be ignored:

• SCRIPT
• STYLE

Attributes

• align: center/end/justify/left/right/start/-moz-center/-webkit-center
• dir: auto/ltr/rtl

Inline stylings

• background: 1 value (color)
  • background-color: currentcolor, hex values, rgb(), hsl() or named colors
  • background-image: url() with support for asset (asset://), data uri, local file (file://) and network image
  • background-repeat: no-repeat/repeat/repeat-x/repeat-y
  • background-position: single or double instances of bottom/center/left/right/top (e.g. top left)
  • background-size: auto/contain/cover
• border: 3 values (width style color), 2 values (width style) or 1 value (width)
  • border-top, border-right, border-bottom, border-left
  • border-block-start, border-block-end
  • border-inline-start, border-inline-end
• border-radius: 4, 3, 2 or 1 value with slash support (e.g. 10px / 20px)
  • border-top-left-radius: 2 values or 1 value in em, pt and px
  • border-top-right-radius: 2 values or 1 value in em, pt and px
  • border-bottom-right-radius: 2 values or 1 value in em, pt and px
  • border-bottom-left-radius: 2 values or 1 value in em, pt and px
• color: hex values, rgb(), hsl() or named colors
• direction (similar to dir attribute)
• display: block/flex/inline/inline-block/none
  • In flex mode:
    • flex-direction: column/row
    • align-items: flex-start/flex-end/center/baseline/stretch
    • gap: value in em, %, pt and px
    • justify-content: flex-start/flex-end/center/space-between/space-around/space-evenly
• font-family
• font-size: absolute (e.g. xx-large), relative (larger, smaller) or values in em, %, pt and px
• font-style: italic/normal
• font-weight: bold/normal/100..900
• line-height: normal, number or value in em, %, pt and px
• margin: 4 values, 2 values or 1 value in em, pt and px
  • margin-top, margin-right, margin-bottom, margin-left
  • margin-block-start, margin-block-end
  • margin-inline-start, margin-inline-end
• padding: 4 values, 2 values or 1 value in em, pt and px
  • padding-top, padding-right, padding-bottom, padding-left
  • padding-block-start, padding-block-end
  • padding-inline-start, padding-inline-end
• vertical-align: baseline/top/bottom/middle/sub/super
• text-align (similar to align attribute)
• text-decoration
  • text-decoration-color: currentcolor, hex values, rgb(), hsl() or named colors
  • text-decoration-line: line-through/none/overline/underline
  • text-decoration-style: dotted/dashed/double/solid
  • text-decoration-thickness, text-decoration-width: values in % only
• text-overflow: clip/ellipsis. Note: text-overflow: ellipsis should be used in conjuntion with max-lines or -webkit-line-clamp for better result.
• text-shadow:
  • 4 values (color x y blur, color x y blur)
  • 3 values (x y color, color x y)
  • Or 2 values (x y)
  • Multiple shadows
• white-space: pre/normal/nowrap
• Sizing: auto or values in em, %, pt and px
  • width, max-width, min-width
  • height, max-height, min-height

Extensibility

The core package implements widget building logic with high testing coverage to ensure correctness. It tries to render an optimal tree by using RichText with specific TextStyle, merging text spans together, showing images in sized box, etc. The idea is to build a solid foundation for apps to customize.

See the extensibility document for detailed information.