898 lines
20 KiB
Markdown
898 lines
20 KiB
Markdown
Flutter 备忘清单
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===
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包含 Flutter 常用的组件、布局、方法等。初学者的完整快速参考
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入门
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---
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### macOS 操作系统上安装和配置
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```bash
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$ sudo softwareupdate --install-rosetta --agree-to-license
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```
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<!--rehype:className=wrap-text-->
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在 [Apple 芯片的 Mac 电脑](https://support.apple.com/zh-cn/HT211814) 上，还需要安装 [Rosetta 2](https://github.com/flutter/website/pull/7119#issuecomment-1124537969) 环境因为 一些辅助工具 仍然需要，通过手动运行上面的命令来安装
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#### 获取 Flutter SDK
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- 安装包来获取最新的 stable Flutter SDK：
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- Intel [`flutter_macos_3.3.8-stable.zip`](https://storage.flutter-io.cn/flutter_infra_release/releases/stable/macos/flutter_macos_3.3.8-stable.zip)
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- Apple 芯片 [`flutter_macos_arm64_3.3.8-stable.zip`](https://storage.flutter-io.cn/flutter_infra_release/releases/stable/macos/flutter_macos_arm64_3.3.8-stable.zip)
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想要获取到其他版本的安装包，请参阅 [SDK 版本列表](https://flutter.cn/docs/development/tools/sdk/releases) 页面
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- 将文件解压到目标路径, 比如:
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```bash
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$ cd ~/development
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$ unzip ~/Downloads/flutter_macos_3.3.8-stable.zip
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```
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<!--rehype:className=wrap-text-->
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- 配置 `flutter` 的 PATH 环境变量：
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```bash
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$ export PATH="$PATH:`pwd`/flutter/bin"
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```
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- 运行 `flutter doctor` 命令
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<!--rehype:className=style-timeline-->
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### Windows 操作系统上安装和配置
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- 点击下方的安装包，获取 stable 发行通道的 Flutter SDK 最新版本：
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- [flutter_windows_3.3.8-stable.zip](https://storage.flutter-io.cn/flutter_infra_release/releases/stable/windows/flutter_windows_3.3.8-stable.zip)
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- 要查看其他发行通道和以往的版本，请参阅 [SDK 版本列表](https://flutter.cn/docs/development/tools/sdk/releases) 页面
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- 将压缩包解压，然后把其中的 `flutter` 目录整个放在你想放置 `Flutter SDK` 的路径中（例如 `C:\src\flutter`）
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- 更新 `path` 环境变量，在开始菜单的搜索功能键入`「env」`，然后选择 `编辑系统环境变量`。在 **`用户变量`** 一栏中，检查是否有 **`Path`** 这个条目：
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- 如果存在这个条目，以 `;` 分隔已有的内容，加入 `flutter\bin` 目录的完整路径。
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- 如果不存在的话，在用户环境变量中创建一个新的 Path 变量，然后将 `flutter\bin` 所在的完整路径作为新变量的值
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<!--rehype:className=style-timeline-->
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如果你不想安装指定版本的安装包。可以忽略步骤 `1` 和 `2`。从 `GitHub` 上的 `Flutter repo` 获取源代码，并根据需要，切换到指定的分支或标签
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```bash
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C:\src>git clone https://github.com/flutter/flutter.git -b stable
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```
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<!--rehype:className=wrap-text-->
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基础组件
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---
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### Text 样式文本
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```dart
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Text("Hello world",
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textAlign: TextAlign.left,
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);
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Text("Hello world! I'm Jack. "*4,
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maxLines: 1,
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overflow: TextOverflow.ellipsis,
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);
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Text("Hello world",
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textScaleFactor: 1.5,
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);
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```
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### TextStyle 指定文本显示的样式
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```dart
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Text("Hello world",
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style: TextStyle(
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color: Colors.blue,
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fontSize: 18.0,
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height: 1.2,
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fontFamily: "Courier",
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background: Paint()..color=Colors.yellow,
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decoration:TextDecoration.underline,
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decorationStyle: TextDecorationStyle.dashed
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),
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);
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```
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<!--rehype:className=wrap-text-->
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### TextSpan 文本的一个“片段”
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```dart
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Text.rich(TextSpan(
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children: [
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TextSpan(
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text: "Home: "
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),
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TextSpan(
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text: "https://flutter.dev",
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style: TextStyle(
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color: Colors.blue
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),
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recognizer: _tapRecognizer
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),
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]
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))
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```
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### DefaultTextStyle 文本默认样式
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<!--rehype:wrap-class=row-span-4-->
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```dart
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DefaultTextStyle(
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// 1.设置文本默认样式
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style: TextStyle(
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color:Colors.red,
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fontSize: 20.0,
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),
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textAlign: TextAlign.start,
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child: Column(
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crossAxisAlignment: CrossAxisAlignment.start,
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children: <Widget>[
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Text("hello world"),
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Text("I am Jack"),
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Text("I am Jack",
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style: TextStyle(
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inherit: false, //2.不继承默认样式
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color: Colors.grey
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),
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),
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],
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),
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);
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```
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<!--rehype:className=wrap-text-->
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### 字体设置加载
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<!--rehype:wrap-class=row-span-4-->
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- 在 asset 中声明，要先在 `pubspec.yaml` 中声明它
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```yaml
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flutter:
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fonts:
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- family: Raleway
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fonts:
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- asset: assets/fonts/Raleway-Regular.ttf
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- asset: assets/fonts/Raleway-Medium.ttf
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weight: 500
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- asset: assets/fonts/Raleway-SemiBold.ttf
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weight: 600
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- family: AbrilFatface
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fonts:
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- asset: assets/fonts/abrilfatface/AbrilFatface-Regular.ttf
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```
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- 将字体文件复制到在 `pubspec.yaml` 中指定的位置
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- 使用字体
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```dart
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// 声明文本样式
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const textStyle = const TextStyle(
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fontFamily: 'Raleway',
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);
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// 使用文本样式
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var buttonText = const Text(
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"Use the font for this text",
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style: textStyle,
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);
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```
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<!--rehype:className=style-timeline-->
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### ElevatedButton "漂浮"按钮
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```dart
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ElevatedButton(
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child: Text("normal"),
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onPressed: () {},
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);
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```
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### TextButton 文本按钮
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```dart
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TextButton(
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child: Text("normal"),
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onPressed: () {},
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)
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```
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### OutlineButton 边框阴影且背景透明按钮
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```dart
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OutlineButton(
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child: Text("normal"),
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onPressed: () {},
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)
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```
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### IconButton 可点击的图标按钮
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```dart
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IconButton(
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icon: Icon(Icons.thumb_up),
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onPressed: () {},
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)
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```
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### 带图标的按钮
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```dart
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ElevatedButton.icon(
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icon: Icon(Icons.send),
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label: Text("发送"),
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onPressed: _onPressed,
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),
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OutlineButton.icon(
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icon: Icon(Icons.add),
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label: Text("添加"),
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onPressed: _onPressed,
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),
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TextButton.icon(
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icon: Icon(Icons.info),
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label: Text("详情"),
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onPressed: _onPressed,
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),
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```
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### 从 asset 中加载图片
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- 在工程根目录下创建一个`images目录`，并将图片 `aaa.png` 拷贝到该目录。
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- 在 `pubspec.yaml` 中的 `flutter` 部分添加如下内容：
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```yaml
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assets:
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- images/aaa.png
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```
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注意: 由于 yaml 文件对缩进严格，所以必须严格按照每一层两个空格的方式进行缩进，此处 assets 前面应有两个空格。
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- 加载该图片
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```dart
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Image(
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image: AssetImage("images/aaa.png"),
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width: 100.0
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);
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```
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Image 也提供了一个快捷的构造函数 `Image.asset` 用于从 `asset` 中加载、显示图片：
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```dart
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Image.asset("images/aaa.png",
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width: 100.0,
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)
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```
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<!--rehype:className=style-timeline-->
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### 从网络加载图片
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```dart
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Image(
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image: NetworkImage(
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"https://avatars2.githubusercontent.com/u/20411648?s=460&v=4"),
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width: 100.0,
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)
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```
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<!--rehype:className=wrap-text-->
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Image 也提供了一个快捷的构造函数 `Image.network` 用于从网络加载、显示图片：
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```dart
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Image.network(
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"https://avatars2.githubusercontent.com/u/20411648?s=460&v=4",
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width: 100.0,
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)
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```
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<!--rehype:className=wrap-text-->
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### Image 参数
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<!--rehype:wrap-class=row-span-2-->
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```dart
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const Image({
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...
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this.width, // 图片的宽
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this.height, // 图片高度
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this.color, // 图片的混合色值
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this.colorBlendMode, // 混合模式
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this.fit,// 缩放模式
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// 对齐方式
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this.alignment = Alignment.center,
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// 重复方式
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this.repeat = ImageRepeat.noRepeat,
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...
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})
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```
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### Switch 单选开关
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```dart
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Switch(
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value: true,//当前状态
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onChanged:(value){
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// 重新构建页面
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},
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),
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```
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### Checkbox 复选框
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<!--rehype:wrap-class=row-span-2-->
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```dart
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Checkbox(
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value: true,
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// 选中时的颜色
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activeColor: Colors.red,
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onChanged:(value){
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// ...
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},
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)
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```
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### TextField 文本输入框
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```dart
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TextField(
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autofocus: true,
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onChanged: (v) {
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print("onChange: $v");
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}
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)
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```
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### LinearProgressIndicator 线性、条状的进度条
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模糊进度条(会执行一个动画)
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```dart
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LinearProgressIndicator(
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backgroundColor: Colors.grey[200],
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valueColor: AlwaysStoppedAnimation(Colors.blue),
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),
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```
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<!--rehype:className=wrap-text-->
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进度条显示 `50%`
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```dart
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LinearProgressIndicator(
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backgroundColor: Colors.grey[200],
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valueColor: AlwaysStoppedAnimation(Colors.blue),
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value: .5,
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)
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```
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<!--rehype:className=wrap-text-->
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### CircularProgressIndicator 圆形进度条
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模糊进度条(会执行一个旋转动画)
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```dart
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CircularProgressIndicator(
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backgroundColor: Colors.grey[200],
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valueColor: AlwaysStoppedAnimation(Colors.blue),
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),
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```
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<!--rehype:className=wrap-text-->
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进度条显示 `50%`，会显示一个半圆
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```dart
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CircularProgressIndicator(
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backgroundColor: Colors.grey[200],
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valueColor: AlwaysStoppedAnimation(Colors.blue),
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value: .5,
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),
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```
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<!--rehype:className=wrap-text-->
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### 自定义尺寸
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线性进度条高度指定为 `3`
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```dart
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SizedBox(
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height: 3,
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child: LinearProgressIndicator(
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backgroundColor: Colors.grey[200],
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valueColor: AlwaysStoppedAnimation(Colors.blue),
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value: .5,
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),
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),
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```
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圆形进度条直径指定为 `100`
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```dart
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SizedBox(
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height: 100,
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width: 100,
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child: CircularProgressIndicator(
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backgroundColor: Colors.grey[200],
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valueColor: AlwaysStoppedAnimation(Colors.blue),
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value: .7,
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),
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),
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```
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基础布局
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---
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### Container
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在实际开发中，Container常常用于对一个组件进行包装修饰。
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```dart
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Container(
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width: 100,
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height: 100,
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color: Colors.blue,
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alignment: Alignment.center,
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child: Text('Hello world'),
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),
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```
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将 `Contianer` 大小固定为 `100 * 100`， 背景色为蓝色。把 `Text` 包裹在 `Container` 中，并将其居中
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### Column
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列布局(Column),可以将多个子组件沿着垂直的方向摆放(竖的摆放)
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```dart
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// 将container 和 button 摆放到同一列。
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Column(
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children: [
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Container(
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width: 100,
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height: 100,
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color: Colors.blue,
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alignment: Alignment.center,
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child: Text('Hello world'),
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),
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ElevatedButton(
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onPressed: () {},
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child: Text('Button'),
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),
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],
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),
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```
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### Row
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行布局(Row)，可以将多个组件沿水平的方向摆放。
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```dart
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Row(
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children: [
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ElevatedButton(
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onPressed: () {},
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child: const Text('1'),
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),
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ElevatedButton(
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onPressed: () {},
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child: const Text('2'),
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),
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ElevatedButton(
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onPressed: () {},
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child: const Text('3'),
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),
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],
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),
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```
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在同一行摆放 3 个 `Button`
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### Wrap
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将子组件从左到右依次排列，当空间不足时自动换行。
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```dart
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Wrap(
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children: [
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FlutterLogo(),
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FlutterLogo(),
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FlutterLogo(),
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FlutterLogo(),
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FlutterLogo(),
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FlutterLogo(),
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],
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),
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```
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显示多个 `Flutter` 的 `logo` 并自动换行
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### Stack
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Stack 可以将一多个子组件叠在一起显示。堆叠顺序按照children属性中的列表依次堆叠摆放，默认将子控件沿左上角对齐。
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需要控制子控件位置可以嵌套`Positoned`控件。
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```dart
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Stack(
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children: [
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Container(
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height: 300,
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width: 300,
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color: Colors.blue,
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),
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Container(
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height: 200,
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width: 200,
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color: Colors.black,
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),
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Container(
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height: 100,
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width: 100,
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color: Colors.yellow,
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),
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],
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),
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```
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依次堆叠 `300*300` 的蓝色色块、`200*200` 的黑色色块、`100*100` 的黄色色块
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### Positioned
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<!--rehype:wrap-class=row-span-2-->
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若需要控制Stack中子控件的位置，则可以嵌套改控件。
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```dart
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Stack(
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children: [
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// 默认摆放在左上位置
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Container(
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height: 300,
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width: 300,
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color: Colors.blue,
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),
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// 距离左边40个、距离上面40个逻辑像素的位置
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Positioned(
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left: 40,
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top: 40,
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child: Container(
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height: 200,
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width: 200,
|
||
color: Colors.black,
|
||
),
|
||
),
|
||
// 距离左边80个、距离上面80个逻辑像素的位置
|
||
Positioned(
|
||
left: 80,
|
||
top: 80,
|
||
child: Container(
|
||
height: 100,
|
||
width: 100,
|
||
color: Colors.yellow,
|
||
),
|
||
),
|
||
],
|
||
),
|
||
```
|
||
|
||
### Align
|
||
|
||
Align组件用于决定子组件对齐方式
|
||
|
||
```dart
|
||
// 使用Align将Button 居中在Container中
|
||
Container(
|
||
width: 100,
|
||
height: 100,
|
||
color: Colors.green,
|
||
child: Align(
|
||
alignment: Alignment.center,
|
||
child: ElevatedButton(
|
||
onPressed: () {},
|
||
child: Text('Center'),
|
||
),
|
||
),
|
||
),
|
||
```
|
||
|
||
### Center
|
||
|
||
Center 组件实际上继承于Align。用于专门剧中。
|
||
|
||
```dart
|
||
//与 Align中代码效果一致
|
||
Container(
|
||
width: 100,
|
||
height: 100,
|
||
color: Colors.green,
|
||
child: Center(
|
||
child: ElevatedButton(
|
||
onPressed: () {},
|
||
child: Text('Center'),
|
||
),
|
||
),
|
||
),
|
||
```
|
||
|
||
### Flex
|
||
|
||
Flex 的用法与 `Row` 或 `Column` 类似，但只需要额外传入 `direction` 参数
|
||
|
||
- `Row` 和 `Column` 组件都继承 `Flex` 组件
|
||
- 设置 `direction` 为 `Axis.horizontal` 表示水平方向(`Row`)，为 `Axis.vertical`则为垂直方向(`Column`)
|
||
|
||
垂直方向依次摆放3个flutter logo
|
||
|
||
```dart
|
||
Flex(
|
||
direction: Axis.vertiacl,
|
||
children: [
|
||
FlutterLogo(),
|
||
FlutterLogo(),
|
||
FlutterLogo(),
|
||
],
|
||
),
|
||
```
|
||
|
||
水平方向依次摆放 3 个 flutter logo
|
||
|
||
```dart
|
||
Flex(
|
||
direction: Axis.horizontal,
|
||
children: [
|
||
FlutterLogo(),
|
||
FlutterLogo(),
|
||
FlutterLogo(),
|
||
],
|
||
),
|
||
```
|
||
|
||
### Expaneded
|
||
<!--rehype:wrap-class=row-span-2-->
|
||
|
||
Expanded 用于扩张一个子组件。可以通过 `flex` 属性，用于表示该组件相对其他弹性组件放大的倍数(可以理解为一个权重)。
|
||
|
||
```dart
|
||
// Container 会占满剩余的全部空用空间
|
||
Row(
|
||
children: [
|
||
FlutterLogo(),
|
||
Expanded(
|
||
child: Container(
|
||
child: FlutterLogo(),
|
||
color: Colors.green,
|
||
),
|
||
),
|
||
FlutterLogo(),
|
||
],
|
||
),
|
||
|
||
// 按照1:2 的比例分配一整行的空间
|
||
Row(
|
||
children: [
|
||
Expanded(
|
||
flex: 1,
|
||
child: Container(
|
||
child: FlutterLogo(),
|
||
color: Colors.green,
|
||
),
|
||
),
|
||
Expanded(
|
||
flex: 2,
|
||
child: Container(
|
||
child: FlutterLogo(),
|
||
color: Colors.blue,
|
||
),
|
||
),
|
||
],
|
||
),
|
||
```
|
||
|
||
### Flexible
|
||
<!--rehype:wrap-class=row-span-2-->
|
||
|
||
`Flexible` 是 `Expanded` 组件的父类。
|
||
与 `Expanded` 不同的是，`Flexible` 可以通过 `fit` 属性设置子控件是否必须占满 `Flexibal` 扩展的空间。而 `Expaned` 默认子控件必须占满
|
||
|
||
```dart
|
||
// 如果将fit设置为tight，
|
||
// 则绿色Container 和蓝色Container大小一样。
|
||
// 如果将fit设置为loose，
|
||
// 则两个Flexible扩展的空间大小是一样的，
|
||
// 但绿色Container并不会填充整个扩展的空间。
|
||
Row(
|
||
children: [
|
||
Flexible(
|
||
flex: 2,
|
||
// fit: FlexFit.tight,
|
||
child: Container(
|
||
child: FlutterLogo(),
|
||
color: Colors.green,
|
||
),
|
||
),
|
||
Expanded(
|
||
flex: 2,
|
||
child: Container(
|
||
child: FlutterLogo(),
|
||
color: Colors.blue,
|
||
),
|
||
),
|
||
],
|
||
),
|
||
```
|
||
|
||
将 `Flexible` 的 `fit` 属性设置为 `tingt`，就等价于使用 `Expanded`
|
||
|
||
### Spacer
|
||
|
||
Spacer 用于在布局中留白
|
||
|
||
```dart
|
||
Row(
|
||
children: [
|
||
Text('Item'),
|
||
Spacer(),
|
||
FlutterLogo(),
|
||
],
|
||
),
|
||
```
|
||
|
||
例如，需要文本和图标位于一个行的两端，而中间留白时。就可以使用 `Spacer`
|
||
|
||
### ListView
|
||
|
||
`ListView` 是一个支持滚动的列表组件。该组件默认支持上下滑动。
|
||
`ListView`的默认构造函数，会立即初始化`children`中的所有子`widget`，无法动态加载。
|
||
|
||
```dart
|
||
ListView(
|
||
children: [
|
||
Text('1'),
|
||
Text('2'),
|
||
Text('3'),
|
||
Text('4'),
|
||
],
|
||
),
|
||
```
|
||
|
||
需要动态加载，则可以使用 `ListView.builder()`命名构函数。
|
||
|
||
```dart
|
||
// 动态生成4个Text
|
||
ListView.builder(
|
||
itemBuilder: (BuildContext context, int index) {
|
||
return Text('$index');
|
||
},
|
||
itemCount: 4,
|
||
),
|
||
```
|
||
|
||
需要在对`ListView`中的`Item`添加分割线，则可以借助`ListView.separated()`。
|
||
|
||
```dart
|
||
// separatorBuilder 函数用于在元素之间插入分割线。
|
||
// 也可以返回其他widget。该widget会被插入各个元素之间。
|
||
ListView.separated(
|
||
itemBuilder: (BuildContext context, int index) {
|
||
return Text('$index');
|
||
},
|
||
itemCount: 4,
|
||
separatorBuilder: (BuildContext context, int index) {
|
||
// 使用Divider widget 画一条粗为5，颜色为红色的线
|
||
return const Divider(
|
||
height: 5,
|
||
thickness: 5,
|
||
color: Colors.red,
|
||
);
|
||
},
|
||
),
|
||
```
|
||
|
||
### GridView
|
||
<!--rehype:wrap-class=col-span-2-->
|
||
`GridView`可将元素显示为二维网格状的列表组件，并支持主轴方向滚动。
|
||
使用GridView() 构造函数，需要传入gridDelegate和children。Flutter中已经提供了两种实现方式，分别是:
|
||
|
||
- `SliverGridDelegateWithFixedCrossAxisCount()` 用于交叉轴方向固定数。
|
||
- `SliverGridDelegateWithMaxCrossAxisExtent()` 用于交叉轴方向限制最大长度。
|
||
|
||
```dart
|
||
// 使用SliverGridDelegateWithFixedCrossAxisCount
|
||
GridView(
|
||
gridDelegate:
|
||
const SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 4),
|
||
children: List.generate(
|
||
8,
|
||
(index) => Container(
|
||
color: Colors.red[index % 8 * 100],
|
||
child: Text("index $index"),
|
||
)),
|
||
),
|
||
|
||
// 使用SliverGridDelegateWithMaxCrossAxisExtent
|
||
GridView(
|
||
gridDelegate:
|
||
SliverGridDelegateWithMaxCrossAxisExtent(maxCrossAxisExtent: 200),
|
||
children: List.generate(
|
||
8,
|
||
(index) => Container(
|
||
color: Colors.red[index % 8 * 100],
|
||
child: Text("index $index"),
|
||
),
|
||
),
|
||
),
|
||
```
|
||
|
||
`GridView.builder()`命名构造可以实现元素的动态加载，与`ListView.builder()`类似
|
||
|
||
```dart
|
||
GridView.builder(
|
||
itemCount: 8,
|
||
gridDelegate: const SliverGridDelegateWithFixedCrossAxisCount(
|
||
crossAxisCount: 4),
|
||
itemBuilder: (context, index) => Container(
|
||
color: Colors.red[index % 8 * 100],
|
||
child: Text("index $index"),
|
||
),
|
||
),
|
||
```
|
||
|
||
`Gridview.count()` 一个简单的构造函数，只需要传入`crossAxisCount`（交叉轴元素的个数）和`children`即可。
|
||
|
||
```dart
|
||
GridView.count(
|
||
crossAxisCount: 4, // 每行固定为4个
|
||
children: List.generate(
|
||
8,
|
||
(index) => Container(
|
||
color: Colors.red[index % 8 * 100],
|
||
child: Text("index $index"),
|
||
)),
|
||
),
|
||
```
|
||
|
||
`GridView.extent()` 用于设定每个元素在交叉轴方向的最大尺寸。当程序运行在较大屏幕时通常能看到更多的元素，而不是少量元素的放大版。通过传入`maxCrossAxisExtent`,`Gridview`会根据屏幕尺寸自动选择合适的行数量。
|
||
|
||
```dart
|
||
GridView.extent(
|
||
maxCrossAxisExtent: 200,
|
||
children: List.generate(
|
||
8,
|
||
(index) => Container(
|
||
color: Colors.red[index % 8 * 100],
|
||
child: Text("index $index"),
|
||
)),
|
||
),
|
||
```
|
||
|
||
`GridView.count()`和GridView.extent()`可以看作GridView的语法糖。
|
||
|
||
### PageView
|
||
|
||
使用`PageView`可以实现整屏页面滚动,默认为水平方向翻页。与`ListView`类似。
|
||
|
||
- `pageSnapping`参数可以设置滑动时`Page`停留在任意位置。
|
||
- `scrollDirection`参数设置滚动方向(默认为水平方向)。
|
||
|
||
```dart
|
||
PageView(
|
||
pageSnapping: false, // 取消页面固定
|
||
scrollDirection: Axis.vertical, // 设置为垂直方向滚动
|
||
children: [
|
||
for (int i = 0; i < 4; i++)
|
||
Container(
|
||
color: Colors.red[i % 4 * 100],
|
||
)
|
||
],
|
||
),
|
||
```
|
||
|
||
使用`PageView.builder()`命名构造，可以动态加载页面。与`ListView.builder()`类似。
|
||
|
||
```dart
|
||
PageView.builder(
|
||
pageSnapping: false,
|
||
scrollDirection: Axis.vertical,
|
||
itemBuilder: (BuildContext context, int index) => Container(
|
||
color: Colors.red[index % 4 * 100],
|
||
),
|
||
),
|
||
```
|
||
|
||
另见
|
||
---
|
||
|
||
- [Dart 备忘清单](./dart.md) _(jaywcjlove.github.io)_
|
||
- [flutter 官网](https://flutter.dev) _(flutter.dev)_
|
||
- [flutter 中文开发者社区](https://flutterchina.club/) _(flutterchina.club)_
|