Package Management

YAML is an intuitive, highly readable and human-readable file format, it's syntax is simple and very easy to parse compared to xml or Json, so YAML is often used for configuration files, Flutter also uses yaml files as its configuration files. the default configuration file for Flutter projects is pubspec.yaml, let's look at a simple example.

name: flutter_in_action
description: First Flutter application.

version: 1.0.0+1

dependencies:
  flutter:
    sdk: flutter
  cupertino_icons: ^0.1.2

dev_dependencies:
  flutter_test:
    sdk: flutter

flutter:
  uses-material-design: true

name: the name of the application or package.
description: description, introduction of the application or package.
version: version number of the application or package.
dependencies: other packages or plugins that the application or package depends on.
dev_dependencies: the toolkits that the development environment depends on (not the packages that the flutter application itself depends on).
flutter: flutter-related configuration options.

If our Flutter application itself depends on a package, we need to add the dependent package under dependencies, next we will demonstrate how to add, download and use third-party packages with an example.

Pub repository

Pub (https://pub.dev/ ) is the official Google repository for Dart Packages.

Example

Next, we implement a widget that displays random strings. there is an open source package called "english_words" that contains thousands of common English words and some useful functions. We first find the package "english_words" on pub (shown in Figure 2-5), determine its latest version number and whether it supports Flutter.

! Figure 2-5

We see that the latest version of the "english_words" package is 3.1.3, and it supports flutter.

add "english_words" (version 3.1.3) to the list of dependencies, as follows.

dependencies:
  flutter:
    sdk: flutter

  cupertino_icons: ^0.1.0
  # New dependencies added
  : ^3.1.3

Download the package. When viewing pubspec.yaml in the editor view of Android Studio (Figure 2-6), click Packages get in the upper right corner.
! Figure 2-6
This will install the dependency packages to your project. We can see the following in the console.
```
flutter packages get
Running "flutter packages get" in flutter_in_action...
Process finished with exit code 0
```
We can also download the dependencies from the console by locating the current project directory and running the flutter packages get command manually. Also, note the difference between dependencies and dev_dependencies, the former dependencies will be compiled as part of the source code of the app to generate the final installer. The latter dependencies are only used as some toolkits in the development stage, mainly to help us improve the development and testing efficiency, such as flutter's automation test package, etc.
introduce the english_words package.
```
import 'package:english_words/english_words.dart';
```
On import, Android Studio will automatically provide suggested options for library import. The line of code will be grayed out after importing, indicating that the imported library is not used yet. 4.

Use english_words package to generate random strings.

class RandomWordsWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
   // Generate random strings
    final wordPair = new WordPair.random();
    return Padding(
      padding: const EdgeInsets.all(8.0),
      child: new Text(wordPair.toString()),
    );
  }
}

We add RandomWordsWidget to the child widget of Column of _MyHomePageState.build.

Column(
  mainAxisAlignment: MainAxisAlignment.center,
  children: <Widget>[
    RandomWordsWidget(),
  ],
)

If the application is running, use the Hot Reload button (⚡️ icon) to update the running application. Each time you click Hot Reload or Save Item, a different word pair is randomly selected in the running application. This is because the word pairs are generated inside the build method. The build method is executed each time a hot update is performed, and runs as shown in Figure 2-7.
! Figure 2-7

Other dependency methods

The dependency methods described above rely on Pub repositories. However, we can also rely on local packages and git repositories.

Reliance on local packages
If we are developing a package locally, named pkg1, we can depend on it by doing the following.
```
dependencies:
    pkg1:
        path: ... /... /code/pkg1
```
Paths can be either relative or absolute.
Dependency on Git: You can also depend on packages stored in a Git repository. If the package is located in the root of the repository, use the following syntax
```
dependencies:
  pkg1:
    git:
      url: git://github.com/xxx/pkg1.git
```
The above assumes that the package is located in the root directory of the Git repository. If this is not the case, you can specify a relative location using the path parameter, e.g.
```
dependencies:
  package1:
    git:
      url: git://github.com/flutter/packages.git
      path: packages/package1
```

These dependencies described above are commonly used in Flutter development, but there are some other dependencies, the complete content of which the reader can see for himself: https://www.dartlang.org/tools/pub/dependencies .

Summary

This section describes the overall process of package management, referencing, and downloading in Flutter, and we will cover how to develop and distribute our own packages in later chapters. Translated with www.DeepL.com/Translator (free version)

Package Management

name: flutter_in_action
description: First Flutter application.

version: 1.0.0+1

dependencies:
  flutter:
    sdk: flutter
  cupertino_icons: ^0.1.2

dev_dependencies:
  flutter_test:
    sdk: flutter

flutter:
  uses-material-design: true

name: the name of the application or package.
description: description, introduction of the application or package.
version: version number of the application or package.
dependencies: other packages or plugins that the application or package depends on.
dev_dependencies: the toolkits that the development environment depends on (not the packages that the flutter application itself depends on).
flutter: flutter-related configuration options.

Pub repository

Pub (https://pub.dev/ ) is the official Google repository for Dart Packages.

Example

! Figure 2-5

We see that the latest version of the "english_words" package is 3.1.3, and it supports flutter.

add "english_words" (version 3.1.3) to the list of dependencies, as follows.

dependencies:
  flutter:
    sdk: flutter

  cupertino_icons: ^0.1.0
  # New dependencies added
  : ^3.1.3

Download the package. When viewing pubspec.yaml in the editor view of Android Studio (Figure 2-6), click Packages get in the upper right corner.
! Figure 2-6
This will install the dependency packages to your project. We can see the following in the console.
```
flutter packages get
Running "flutter packages get" in flutter_in_action...
Process finished with exit code 0
```
We can also download the dependencies from the console by locating the current project directory and running the flutter packages get command manually. Also, note the difference between dependencies and dev_dependencies, the former dependencies will be compiled as part of the source code of the app to generate the final installer. The latter dependencies are only used as some toolkits in the development stage, mainly to help us improve the development and testing efficiency, such as flutter's automation test package, etc.
introduce the english_words package.
```
import 'package:english_words/english_words.dart';
```
On import, Android Studio will automatically provide suggested options for library import. The line of code will be grayed out after importing, indicating that the imported library is not used yet. 4.

Use english_words package to generate random strings.

class RandomWordsWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
   // Generate random strings
    final wordPair = new WordPair.random();
    return Padding(
      padding: const EdgeInsets.all(8.0),
      child: new Text(wordPair.toString()),
    );
  }
}

We add RandomWordsWidget to the child widget of Column of _MyHomePageState.build.

Column(
  mainAxisAlignment: MainAxisAlignment.center,
  children: <Widget>[
    RandomWordsWidget(),
  ],
)

If the application is running, use the Hot Reload button (⚡️ icon) to update the running application. Each time you click Hot Reload or Save Item, a different word pair is randomly selected in the running application. This is because the word pairs are generated inside the build method. The build method is executed each time a hot update is performed, and runs as shown in Figure 2-7.
! Figure 2-7

Other dependency methods

The dependency methods described above rely on Pub repositories. However, we can also rely on local packages and git repositories.

Reliance on local packages
If we are developing a package locally, named pkg1, we can depend on it by doing the following.
```
dependencies:
    pkg1:
        path: ... /... /code/pkg1
```
Paths can be either relative or absolute.
Dependency on Git: You can also depend on packages stored in a Git repository. If the package is located in the root of the repository, use the following syntax
```
dependencies:
  pkg1:
    git:
      url: git://github.com/xxx/pkg1.git
```
The above assumes that the package is located in the root directory of the Git repository. If this is not the case, you can specify a relative location using the path parameter, e.g.
```
dependencies:
  package1:
    git:
      url: git://github.com/flutter/packages.git
      path: packages/package1
```

Summary

This section describes the overall process of package management, referencing, and downloading in Flutter, and we will cover how to develop and distribute our own packages in later chapters.

Package Management

Pub repository​

Example​

Other dependency methods​

Summary​

Package Management

Pub repository​

Example​

Other dependency methods​

Summary​

Pub repository

Example

Other dependency methods

Summary

Pub repository

Example

Other dependency methods

Summary