Flutter的进度指示器

Flutter CircularProgressIndicator 是一个材质小部件，用于指示应用程序是否繁忙。首先，我们使用 Visual Studio Code(IDE)创建一个名为“progressindicator”的新项目。您可以选择任何名称。

脚步：

1.调用视图 > 命令面板。

2. 输入“flutter”，然后选择Flutter: New Project。

3.输入项目名称并按 Enter。

4.为新项目文件夹创建父目录。

更新插件进度对话框：pubspec.yaml 目录中的 ^1.2.0 应如下所示

name: progressindicator
description: A new Flutter project.

# The following defines the version and build number for your application.
# A version number is three numbers separated by dots, like 1.2.43
# followed by an optional build number separated by a +.
# Both the version and the builder number may be overridden in flutter
# build by specifying --build-name and --build-number, respectively.
# In Android, build-name is used as versionName while build-number used as versionCode.
# Read more about Android versioning at https://developer.android.com/studio/publish/versioning
# In iOS, build-name is used as CFBundleShortVersionString 
# while build-number used as CFBundleVersion.
# Read more about iOS versioning at
# https://developer.apple.com/library/archive/documentation/General
        /Reference/InfoPlistKeyReference/Articles/CoreFoundationKeys.html
version: 1.0.0+1

environment:
  sdk: ">=2.1.0 <3.0.0"

dependencies:
  flutter:
    sdk: flutter

  # The following adds the Cupertino Icons font to your application.
  # Use with the CupertinoIcons class for iOS style icons.
  cupertino_icons: ^0.1.2
  progress_dialog: ^1.2.0

dev_dependencies:
  flutter_test:
    sdk: flutter


# For information on the generic Dart part of this file, see the
# following page: https://dart.dev/tools/pub/pubspec

# The following section is specific to Flutter.
flutter:

  # The following line ensures that the Material Icons font is
  # included with your application, so that you can use the icons in
  # the material Icons class.
  uses-material-design: true

  # To add assets to your application, add an assets section, like this:
  # assets:
  #  - images/a_dot_burr.jpeg
  #  - images/a_dot_ham.jpeg

  # An image asset can refer to one or more resolution-specific "variants", see
  # https://flutter.dev/assets-and-images/#resolution-aware.

  # For details regarding adding assets from package dependencies, see
  # https://flutter.dev/assets-and-images/#from-packages

  # To add custom fonts to your application, add a fonts section here,
  # in this "flutter" section. Each entry in this list should have a
  # "family" key with the font family name, and a "fonts" key with a
  # list giving the asset and other descriptors for the font. For
  # example:
  # fonts:
  #   - family: Schyler
  #     fonts:
  #       - asset: fonts/Schyler-Regular.ttf
  #       - asset: fonts/Schyler-Italic.ttf
  #         style: italic
  #   - family: Trajan Pro
  #     fonts:
  #       - asset: fonts/TrajanPro.ttf
  #       - asset: fonts/TrajanPro_Bold.ttf
  #         weight: 700
  #
  # For details regarding fonts from package dependencies,
  # see https://flutter.dev/custom-fonts/#from-packages

现在更新进度对话框flutter包。

创建一个名为 main.js 的文件。dart如下：

Dart

import 'package:flutter/material.dart';
import 'package:progress_dialog/progress_dialog.dart';
   
ProgressDialog pr;
   
void main() {
  runApp(MaterialApp(
    home: FirstScreen(),
  ));
}
   
class FirstScreen extends StatefulWidget {
  @override
  _FirstScreenState createState() => _FirstScreenState();
}
   
class _FirstScreenState extends State {
  ProgressDialog pr;
   
  @override
  // Add the CSS details of the page
  Widget build(BuildContext context) {
    pr = new ProgressDialog(context);
    pr.style(
          message: 'processing',
          borderRadius: 8.0,
          backgroundColor: Colors.white,
          progressWidget: CircularProgressIndicator(),
          elevation: 8.0,
          insetAnimCurve: Curves.easeInOut,
          progress: 0.0,
          maxProgress: 100.0,
          progressTextStyle: TextStyle(
            color: Colors.white, fontSize: 13.0,
            fontWeight: FontWeight.w400),
          messageTextStyle: TextStyle(
            color: Colors.white, fontSize: 19.0,
            fontWeight: FontWeight.w600)
        );
   
    return Scaffold(
      appBar: AppBar(
        // Define the design
          title: const Text('GeeksForGeeks'),
          backgroundColor: Colors.green,),
      body: Center(
          
        child: RaisedButton(
          child: Text('Click here..',
              style: TextStyle(color: Colors.white)),
          color: Colors.green,
          onPressed: () {
            pr.show();
            Future.delayed(Duration(seconds: 2)).then((value) {
              pr.hide().whenComplete(() {
                Navigator.of(context).push(MaterialPageRoute(
                    builder: 
                  (BuildContext context) => SecondScreen()));
              });
            });
          },
        ),
      ),
    );
  }
}
   
class SecondScreen extends StatefulWidget {
  @override
  _SecondScreenState createState() => _SecondScreenState();
}
   
class _SecondScreenState extends State {
  @override
  // Define the child 
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: RaisedButton(
          onPressed: () => Navigator.of(context).pop(),
          child: Text('Back',
              style: TextStyle(color: Colors.white)),
          color: Colors.green,
        ),
      ),
    );
  }
}

输出 ：

完整代码可在github.com/progressIndicator上找到