Flutter使用flutter_gen管理资源文件-编程知识

pub地址：

https://pub.dev/packages/flutter_gen

1.添加依赖

在你的pubspec.yaml文件中添加flutter_gen作为开发依赖

dependencies:build_runner:flutter_gen_runner:

2.配置pubspec.yaml

在pubspec.yaml文件中，配置flutter_gen的参数。指定输出路径和资源路径。

flutter_gen:output: lib/gen/ # Optional (default: lib/gen/)lineLength: 80   # Optional (default: 80)# Optionalintegrations:flutter_svg: true   # .svg  Assets.images.icons.paint.svg()flare_flutter: true # .flr  Assets.flare.penguin.flare()rive: true          # .flr  Assets.rive.vehicles.rive()lottie: true        # .json Assets.lottie.hamburgerArrow.lottie()colors:inputs:- assets/colors/colors.xmlflutter:uses-material-design: trueassets:- assets/images/tab_home_default.png- assets/images/tab_home_selected.png- assets/images/tab_category_default.png- assets/images/tab_category_selected.png- assets/images/tab_mine_default.png- assets/images/tab_mine_selected.png- assets/images/photo.png- assets/images/font.png- assets/files/mov_file.mov- assets/files/mp3_file.mp3- assets/files/mp4_file.mp4- assets/files/pdf_file.pdf- assets/files/svga_file.svga- assets/files/txt_file.txt- assets/files/xlsx_file.xlsx- assets/files/zip_file.zipfonts:- family: simkaifonts:- asset: assets/fonts/simkai.ttf- family: SourceHanSerifCNBoldfonts:- asset: assets/fonts/SourceHanSerifCN-Bold.otfweight: 700

3.运行生成命令

使用Flutter命令行工具运行pub get来安装新的依赖

$ flutter pub get

使用命令行工具运行命令生成资源文件

$ dart run build_runner build
或
$ flutter packages pub run build_runner build
或
$ flutter packages pub run build_runner build --delete-conflicting-outputs

如果图片资源发生变化，只需更新pubspec.yaml文件并重新运行生成资源文件的命令即可更新资源引用。

4.使用图片和其它资源文件

flutter_gen会在指定的输出目录（例如lib/gen/）中生成一个assets.gen.dart文件，里面包含了所有的资源引用。

使用图片

import 'gen/assets.gen.dart';Image.asset(Assets.images.photo.path, //'assets/images/photo.png',width: 50,height: 50,
),Assets.images.font.image(width: 100,height: 100,
)

使用其它文件

import 'package:flutter/services.dart' show rootBundle;
import 'dart:typed_data';var arr = [Assets.files.txtFile,Assets.files.movFile,Assets.files.mp3File,Assets.files.mp4File,Assets.files.pdfFile,Assets.files.svgaFile,Assets.files.xlsxFile,Assets.files.zipFile];// 获取文件中的字符串
Future<String> loadAsset(String path) async {try {var str = await rootBundle.loadString(path);return str;} catch (e) {return "获取失败";}
}// 获取文件二进制数据
Future<ByteData> loadAssetData(String path) async {try {var data = await rootBundle.load(path);return data;} catch (e) {return ByteData(0);}
}Column(mainAxisAlignment: MainAxisAlignment.center,children: [FutureBuilder<String>(future: loadAsset(Assets.files.txtFile),builder: (BuildContext context,AsyncSnapshot<String> snapshot) {if (snapshot.connectionState == ConnectionState.done) {return Text(snapshot.data ?? '');} else {return const CircularProgressIndicator();}},),FutureBuilder<ByteData>(future: loadAssetData(Assets.files.mp3File),builder: (BuildContext context,AsyncSnapshot<ByteData> snapshot) {if (snapshot.connectionState == ConnectionState.done) {// 这里你可以使用 snapshot.data 来访问文件的二进制数据Uint8List data =snapshot.data?.buffer.asUint8List() ??Uint8List(0);return Container(child: Text(data.toString()),);} else {return const CircularProgressIndicator();}},),],),

资源文件适配

Flutter默认会按照这样的文件夹结构来寻找合适的资源：

.../image.png — 默认图片，适用于1.0x设备像素比的屏幕。
.../2.0x/image.png — 适用于2.0x设备像素比的屏幕。
.../3.0x/image.png — 适用于3.0x设备像素比的屏幕。

当你在应用中引用图像时，只需引用默认的图片路径（.../image.png），Flutter会自动根据设备的像素密度来加载正确的资源文件。如果你的应用不需要支持多种像素密度的图像，那么你也可以只提供默认的图像资源而不创建这些文件夹。

如果你决定支持不同的像素密度，确保为每个分辨率提供相应的图像资源，并按照上述结构放置它们。这样，Flutter就可以为不同的设备屏幕自动选择最合适的资源。

flutter_gen生成的assets.gen.dart

/// GENERATED CODE - DO NOT MODIFY BY HAND
/// *****************************************************
///  FlutterGen
/// *****************************************************// coverage:ignore-file
// ignore_for_file: type=lint
// ignore_for_file: directives_ordering,unnecessary_import,implicit_dynamic_list_literal,deprecated_member_useimport 'package:flutter/widgets.dart';class $AssetsFilesGen {const $AssetsFilesGen();/// File path: assets/files/mov_file.movString get movFile => 'assets/files/mov_file.mov';/// File path: assets/files/mp3_file.mp3String get mp3File => 'assets/files/mp3_file.mp3';/// File path: assets/files/mp4_file.mp4String get mp4File => 'assets/files/mp4_file.mp4';/// File path: assets/files/pdf_file.pdfString get pdfFile => 'assets/files/pdf_file.pdf';/// File path: assets/files/svga_file.svgaString get svgaFile => 'assets/files/svga_file.svga';/// File path: assets/files/txt_file.txtString get txtFile => 'assets/files/txt_file.txt';/// File path: assets/files/xlsx_file.xlsxString get xlsxFile => 'assets/files/xlsx_file.xlsx';/// File path: assets/files/zip_file.zipString get zipFile => 'assets/files/zip_file.zip';/// List of all assetsList<String> get values => [movFile,mp3File,mp4File,pdfFile,svgaFile,txtFile,xlsxFile,zipFile];
}class $AssetsImagesGen {const $AssetsImagesGen();/// File path: assets/images/font.pngAssetGenImage get font => const AssetGenImage('assets/images/font.png');/// File path: assets/images/photo.pngAssetGenImage get photo => const AssetGenImage('assets/images/photo.png');/// File path: assets/images/tab_category_default.pngAssetGenImage get tabCategoryDefault =>const AssetGenImage('assets/images/tab_category_default.png');/// File path: assets/images/tab_category_selected.pngAssetGenImage get tabCategorySelected =>const AssetGenImage('assets/images/tab_category_selected.png');/// File path: assets/images/tab_home_default.pngAssetGenImage get tabHomeDefault =>const AssetGenImage('assets/images/tab_home_default.png');/// File path: assets/images/tab_home_selected.pngAssetGenImage get tabHomeSelected =>const AssetGenImage('assets/images/tab_home_selected.png');/// File path: assets/images/tab_mine_default.pngAssetGenImage get tabMineDefault =>const AssetGenImage('assets/images/tab_mine_default.png');/// File path: assets/images/tab_mine_selected.pngAssetGenImage get tabMineSelected =>const AssetGenImage('assets/images/tab_mine_selected.png');/// List of all assetsList<AssetGenImage> get values => [font,photo,tabCategoryDefault,tabCategorySelected,tabHomeDefault,tabHomeSelected,tabMineDefault,tabMineSelected];
}class Assets {Assets._();static const $AssetsFilesGen files = $AssetsFilesGen();static const $AssetsImagesGen images = $AssetsImagesGen();
}class AssetGenImage {const AssetGenImage(this._assetName);final String _assetName;Image image({Key? key,AssetBundle? bundle,ImageFrameBuilder? frameBuilder,ImageErrorWidgetBuilder? errorBuilder,String? semanticLabel,bool excludeFromSemantics = false,double? scale,double? width,double? height,Color? color,Animation<double>? opacity,BlendMode? colorBlendMode,BoxFit? fit,AlignmentGeometry alignment = Alignment.center,ImageRepeat repeat = ImageRepeat.noRepeat,Rect? centerSlice,bool matchTextDirection = false,bool gaplessPlayback = false,bool isAntiAlias = false,String? package,FilterQuality filterQuality = FilterQuality.low,int? cacheWidth,int? cacheHeight,}) {return Image.asset(_assetName,key: key,bundle: bundle,frameBuilder: frameBuilder,errorBuilder: errorBuilder,semanticLabel: semanticLabel,excludeFromSemantics: excludeFromSemantics,scale: scale,width: width,height: height,color: color,opacity: opacity,colorBlendMode: colorBlendMode,fit: fit,alignment: alignment,repeat: repeat,centerSlice: centerSlice,matchTextDirection: matchTextDirection,gaplessPlayback: gaplessPlayback,isAntiAlias: isAntiAlias,package: package,filterQuality: filterQuality,cacheWidth: cacheWidth,cacheHeight: cacheHeight,);}ImageProvider provider({AssetBundle? bundle,String? package,}) {return AssetImage(_assetName,bundle: bundle,package: package,);}String get path => _assetName;String get keyName => _assetName;
}

5.使用颜色资源文件

flutter_gen会在指定的输出目录（例如lib/gen/）中生成一个colors.gen.dart文件，里面包含了颜色的资源引用。

使用颜色

import 'gen/colors.gen.dart';child: Column(mainAxisAlignment: MainAxisAlignment.center,children: [const Text("字符串1",style: TextStyle(color: Colors.red,),),const Text("字符串1",style: TextStyle(color: ColorName.textColor,),),Text("字符串3",style: TextStyle(color: ColorName.themeColor[300],),),Text("字符串4",style: TextStyle(color: ColorName.themeColorAccent[400],),),],),

colors.xml

<?xml version="1.0" encoding="utf-8"?>
<resources><color name="black">#FF000000</color><color name="white">#FFFFFFFF</color><color name="text_color" type="material">#333333</color><color name="theme_color" type="material material-accent">#333333</color>
</resources>

flutter_gen生成的colors.gen.dart

/// GENERATED CODE - DO NOT MODIFY BY HAND
/// *****************************************************
///  FlutterGen
/// *****************************************************// coverage:ignore-file
// ignore_for_file: type=lint
// ignore_for_file: directives_ordering,unnecessary_import,implicit_dynamic_list_literal,deprecated_member_useimport 'package:flutter/painting.dart';
import 'package:flutter/material.dart';class ColorName {ColorName._();/// Color: #FF000000static const Color black = Color(0xFF000000);/// MaterialColor:///   50: #FFE7E7E7///   100: #FFC2C2C2///   200: #FF999999///   300: #FF707070///   400: #FF525252///   500: #FF333333///   600: #FF2E2E2E///   700: #FF272727///   800: #FF202020///   900: #FF141414static const MaterialColor textColor = MaterialColor(0xFF333333,<int, Color>{50: Color(0xFFE7E7E7),100: Color(0xFFC2C2C2),200: Color(0xFF999999),300: Color(0xFF707070),400: Color(0xFF525252),500: Color(0xFF333333),600: Color(0xFF2E2E2E),700: Color(0xFF272727),800: Color(0xFF202020),900: Color(0xFF141414),},);/// MaterialColor:///   50: #FFE7E7E7///   100: #FFC2C2C2///   200: #FF999999///   300: #FF707070///   400: #FF525252///   500: #FF333333///   600: #FF2E2E2E///   700: #FF272727///   800: #FF202020///   900: #FF141414static const MaterialColor themeColor = MaterialColor(0xFF333333,<int, Color>{50: Color(0xFFE7E7E7),100: Color(0xFFC2C2C2),200: Color(0xFF999999),300: Color(0xFF707070),400: Color(0xFF525252),500: Color(0xFF333333),600: Color(0xFF2E2E2E),700: Color(0xFF272727),800: Color(0xFF202020),900: Color(0xFF141414),},);/// MaterialAccentColor:///   100: #FFE82D2D///   200: #FFC21616///   400: #FFBE0000///   700: #FFAF0000static const MaterialAccentColor themeColorAccent = MaterialAccentColor(0xFFC21616,<int, Color>{100: Color(0xFFE82D2D),200: Color(0xFFC21616),400: Color(0xFFBE0000),700: Color(0xFFAF0000),},);/// Color: #FFFFFFFFstatic const Color white = Color(0xFFFFFFFF);
}

6.使用字体资源文件

flutter_gen会在指定的输出目录（例如lib/gen/）中生成一个colors.gen.dart文件，里面包含了颜色的资源引用。

使用字体

import 'gen/fonts.gen.dart';const Text("字体",style: TextStyle(fontFamily: FontFamily.simkai,fontFamilyFallback: [FontFamily.sourceHanSerifCNBold],),
),

通常，fontFamilyFallback用于指定一系列的备选字体，以确保在主字体不支持某些字符时，文本仍然可以用其他字体显示。如果你确定FontFamily.simkai能够支持你需要显示的所有字符，那么就不需要在fontFamilyFallback中再次指定它。相反，如果你有理由相信FontFamily.simkai可能不包含某些字符，那么应该在fontFamilyFallback中指定一个或多个不同的备选字体。

flutter_gen生成的fonts.gen.dart

/// GENERATED CODE - DO NOT MODIFY BY HAND
/// *****************************************************
///  FlutterGen
/// *****************************************************// coverage:ignore-file
// ignore_for_file: type=lint
// ignore_for_file: directives_ordering,unnecessary_import,implicit_dynamic_list_literal,deprecated_member_useclass FontFamily {FontFamily._();/// Font family: SourceHanSerifCNBoldstatic const String sourceHanSerifCNBold = 'SourceHanSerifCNBold';/// Font family: simkaistatic const String simkai = 'simkai';
}