Removal of AssetManifest.json
Summary
#Flutter apps currently include an asset file named AssetManifest.json
.
This file effectively contains a list of assets.
Application code can read it using the AssetBundle
API to
determine what assets are available at runtime.
The AssetManifest.json
file is an undocumented implementation detail.
It's no longer used by the framework, so it will no longer be
generated in a future release of Flutter.
If your application code needs to get a list of available assets, use
the AssetManifest
API instead.
Migration guide
#Reading asset manifest from Flutter application code
#Before:
import 'dart:convert';
import 'package:flutter/services.dart';
final String assetManifestContent = await rootBundle.loadString('AssetManifest.json');
final Map<Object?, Object?> decodedAssetManifest =
json.decode(assetManifestContent) as Map<String, Object?>;
final List<String> assets = decodedAssetManifest.keys.toList().cast<String>();
After:
import 'package:flutter/services.dart';
final AssetManifest assetManifest = await AssetManifest.loadFromAssetBundle(rootBundle);
final List<String> assets = assetManifest.listAssets();
Reading asset manifest information from Dart code outside of a Flutter app
#The flutter
CLI tool generates a new file, AssetManifest.bin
.
This replaces AssetManifest.json
.
This file contains the same information as AssetManifest.json
,
but in a different format.
If you need to read this file from code that is not part of a
Flutter app, and therefore can't use the AssetManifest
API,
you can still parse the file yourself.
The standard_message_codec package can be used to parse the contents.
import 'dart:io';
import 'dart:typed_data';
import 'package:standard_message_codec/standard_message_codec.dart';
void main() {
// The path to AssetManifest.bin depends on the target platform.
final String pathToAssetManifest = './build/web/assets/AssetManifest.bin';
final Uint8List manifest = File(pathToAssetManifest).readAsBytesSync();
final Map<Object?, Object?> decoded = const StandardMessageCodec()
.decodeMessage(ByteData.sublistView(manifest));
final List<String> assets = decoded.keys.cast<String>().toList();
}
Keep in mind that AssetManifest.bin
is an implementation detail of Flutter.
Reading this file is not an officially supported workflow. The contents or
format of the file may change in a future release without announcement.
Timeline
#AssetManifest.json
will no longer be generated starting with the fourth stable
release after 3.19 or one year after the release of 3.19, whichever comes later.
References
#Relevant issues:
- When building a Flutter app, the flutter tool generates an AssetManifest.json file that is unused by the framework (Issue #143577)
除非另有说明,本文档之所提及适用于 Flutter 的最新稳定版本,本页面最后更新时间: 2024-10-09。 查看文档源码 或者 为本页面内容提出建议。