【Flutter】Handling loading status in Flutter

I. Introduction

Today we will discuss how to control the loading state in Flutter.

Flutter, as an efficient and concise UI framework, has been widely used around the world. Handling the loading state is a seemingly simple topic, but in fact it has a huge impact on user experience. Properly displaying the loading status can make our application look smoother and prevent users from being confused and uneasy while waiting for data to be loaded.

If you want to learn more about Flutter and master more techniques and best practices, I have good news for you: we have a comprehensive Flutter column -> Flutter Developer 101 Getting Started Booklet waiting for you. There, you will get complete and systematic Flutter learning materials, including detailed code examples and in-depth concept analysis. What's more, our columns are constantly being updated and improved, and the price will gradually increase with the enrichment of content. So, join now and you will get all the content at the best price. Now, let’s start today’s study!

2. Handle loading status in Flutter

In Flutter, we have many ways to control the loading state. The most basic way is to use Stateful Widget. Stateful Widget allows us to re-render the widget when its state changes, which is very useful for controlling the loading state. At the same time, we can also use some state management libraries, such as Provider or Riverpod, to help us better manage state.

3. Demonstrate with specific business logic code examples

Okay, let's take a look at how to control the loading state in Flutter through a specific business logic code example. In this example, we will call an API to get data and then display the data. During the process of fetching data, we will display a loading indicator.

class Example extends StatefulWidget {
    
    
  @override
  _ExampleState createState() => _ExampleState();
}

class _ExampleState extends State<Example> {
    
    
  bool _isLoading = false; // 控制 loading 状态的变量

  @override
  Widget build(BuildContext context) {
    
    
    return Scaffold(
      body: _isLoading 
          ? Center(child: CircularProgressIndicator()) // 如果正在加载，展示 loading 指示器
          : Center(child: Text('数据加载完成！')); // 否则展示其他内容
  }

  void fetchData() {
    
    
    setState(() {
    
    
      _isLoading = true; // 开始加载数据，设置 _isLoading 为 true
    });

    // 这里是调用 API 的逻辑，我们在这里用注释代替
    // ...

    setState(() {
    
    
      _isLoading = false; // 数据加载完成，设置 _isLoading 为 false
    });
  }
}

In this example, we create a Stateful Widget and add a _isLoadingvariable to its state to control the loading state. When we call fetchDatathe method to get the data, we first set it _isLoadingto true, and then after the data is loaded, we _isLoadingset it to false. In this way, we can _isLoadingcontrol whether to display the loading indicator through variables.

4. Common problems and solutions

We may encounter some problems when handling the loading state. For example, how to handle the loading status when an API call fails or a network error occurs? We can fetchDatasolve this problem by adding error handling logic in the method. In the logical part of calling the API, we can add a try-catch structure to catch possible errors and then set it _isLoadingto false in the catch block.

void fetchData() {
    
    
  setState(() {
    
    
    _isLoading = true; // 开始加载数据，设置 _isLoading 为 true
  });

  try {
    
    
    // 这里是调用 API 的逻辑，我们在这里用注释代替
    // ...
  } catch (e) {
    
    
    print(e); // 打印错误信息
  } finally {
    
    
    setState(() {
    
    
      _isLoading = false; // 无论成功或失败，数据加载完成后，设置 _isLoading 为 false
    });
  }
}

This way, regardless of whether the API call is successful or not, we can ensure _isLoadingthat will be set to false, thus stopping the loading indicator from showing.

5. Conclusion

So far, we have learned how to control the loading state in Flutter. We learned that controlling the loading state can not only improve the user experience, but also help us better handle possible errors. Through a simple example, we demonstrated how to manage the loading state through Stateful Widget and state management library.

If you are interested in Flutter and want to learn more in-depth, then I would like to recommend you a great resource: our Flutter column->Flutter Developer 101 Getting Started Booklet . There, you will get complete and systematic Flutter learning materials, including detailed code examples and in-depth concept analysis. For example, do you know how to build a complete application using Flutter? In our column, you'll find the answers. More importantly, our columns are constantly being updated and improved, and the price will gradually increase as the content becomes richer. So, join now and you will get all the content at the best price. Let's continue exploring in the world of Flutter together! If you want to know more, you can first read our one-stop solution to your needs, Flutter Developer 101 Getting Started Booklet Column Guide .