Skip to content

Instantly share code, notes, and snippets.

What would you like to do?
import 'package:flutter/foundation.dart';
import 'package:flutter/widgets.dart';
import 'package:flutter_svg/flutter_svg.dart';
import 'package:xml/xml.dart';
import 'package:flutter/services.dart';
/// An example widget which uses an [SvgOverride] widget to render an SVG with dynamic colors.
class ZenButtonCookie extends StatelessWidget {
final CookieColor color; // My internal color object. Adapt this for your needs.
const ZenButtonCookie(this.color);
Widget build(BuildContext context) {
return SvgOverride(
hash(path, color),
(elem) => processElement(elem, color),
/// Ensure that the hash uniquely represents the XML transformations performed.
static hash(String svgPath, CookieColor color) => hashValues(svgPath, color?.base, color?.edge);
// Do XML attributes manipulation magic here
static processElement(XmlElement elem, CookieColor color) {
var setAttr = SvgOverride.setAttr;
var getHex = SvgOverride.getHex;
switch (elem.getAttribute('class')) {
case 'base':
setAttr(elem, "fill", getHex(color?.base));
case 'edge':
setAttr(elem, "fill", getHex(color?.edge));
/// A SVG widget which allows the ability to override SVG element attributes.
class SvgOverride extends SvgPicture {
/// Ensure that [cacheHash] uniquely represents the XML transformations performed.
String svgPath,
int cacheHash,
void Function(XmlElement) processElement, {
double width = double.infinity,
double height = double.infinity,
BoxFit fit = BoxFit.contain,
Alignment alignment =,
bool canDrawOutOfView = false,
}) : super(
svgOverrideDecoder(processElement, canDrawOutOfView),
width: width,
height: height,
fit: fit,
alignment: alignment,
allowDrawingOutsideViewBox: canDrawOutOfView,
/// Updates XMLs attributes of an SVG before parsing the SVG itself.
static svgOverrideDecoder(
void Function(XmlElement) processElement, canDrawOutOfView) =>
(String raw, ColorFilter colorFilter, String key) async {
raw = parseXmlFromString(raw, processElement);
return svg.svgPictureStringDecoder(
raw, canDrawOutOfView, colorFilter, key);
/// Parses an XML from a string and processes the attributes.
static String parseXmlFromString(
String xml, void Function(XmlElement) processElement) {
var root = parse(xml);
var elements = root.descendants.whereType<XmlElement>();
return root.toXmlString();
/// Sets the value of an attribute or creates the attribute if it doesn't exist.
static setAttr(XmlElement elem, String attr, String value) {
var attribute = elem.getAttributeNode(attr);
if (attribute == null) {
attribute = XmlAttribute(XmlName(attr), value);
} else {
attribute.value = value;
/// Converts a color into a hex string. Prefixes a cacheHash sign if [leadingHashSign] is true.
static String getHex(Color color, {bool leadingHashSign = true}) =>
color == null
? ""
: '${leadingHashSign ? '#' : ''}'
'${color.alpha.toRadixString(16).padLeft(2, '0')}'
'${, '0')}'
'${, '0')}'
'${, '0')}';
class DynamicAssetPicture extends ExactAssetPicture {
final int cacheHash;
const DynamicAssetPicture(
String assetName, this.cacheHash, PictureInfoDecoder<String> decoder)
: super(decoder, assetName);
Future<OverrideSvgKey> obtainKey(PictureConfiguration picture) {
return SynchronousFuture<OverrideSvgKey>(
bundle: bundle ?? picture.bundle ?? rootBundle,
name: keyName,
colorFilter: colorFilter,
cacheHash: cacheHash,
bool operator ==(dynamic other) =>
runtimeType == other.runtimeType && cacheHash == other.cacheHash;
int get hashCode => hashValues(super.hashCode, cacheHash);
class OverrideSvgKey extends AssetBundlePictureKey {
final int cacheHash;
const OverrideSvgKey(
{AssetBundle bundle, String name, ColorFilter colorFilter, this.cacheHash})
: super(bundle: bundle, name: name, colorFilter: colorFilter);
bool operator ==(dynamic other) => hashCode == other.hashCode;
int get hashCode => hashValues(super.hashCode, cacheHash);

This comment has been minimized.

Copy link
Owner Author

kangabru commented May 30, 2020

Update SVGs dynamically in Flutter! Read about it here.

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
You can’t perform that action at this time.