Скачать или смотреть How to Handle Sequential Async Functions in Dart/Flutter Without Parallel Execution

Learn how to ensure that multiple async functions execute in sequence while waiting for responses in Dart/Flutter, especially for BLE communication.
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Handling Sequential Async Functions in Dart/Flutter for BLE Communication

In the world of Flutter app development, dealing with asynchronous programming can sometimes feel like a challenge—especially when working with Bluetooth Low Energy (BLE) devices. A common scenario involves sending commands to a BLE device and waiting for responses before sending the next command. If you've found yourself in this situation and are looking for a way to ensure that your async functions execute sequentially without threading issues, you’re in the right place.

The Problem

When sending commands over BLE using GATT (Generic Attribute Profile), it is essential to process responses before moving on to the next command. As per the flow, your code might look something like this:

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However, the challenge arises because the await keyword only waits for the completion of a Future, not for the actual response from the BLE device. This can lead to situations where commands are executed out of order, causing unexpected results.

Example Scenario

You might have code that looks like this:

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In this example, command2 may return results before command1, which is not the desired behavior. The key issue here is ensuring that you wait for the response of the first command before sending the second command.

The Solution: Creating a Helper Function

To solve this problem, you can create a helper function that not only writes the command but also waits for the corresponding response. Here's how you can do it effectively:

1. Define a Helper Function

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2. Use the Helper Function to Send Commands Sequentially

Now you can easily await the responses for each command before proceeding to the next one, like so:

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Benefits of This Approach

Safety: Ensures that the next command is not sent until the response for the previous command is received, maintaining the integrity of the flow.

Readability: The code becomes cleaner and easier to understand since the logic for reading and writing is encapsulated in a separate function.

Flexibility: This helper function can be reused for any command, making your codebase more maintainable.

Conclusion

By using the helper function approach, you can effectively manage multiple asynchronous commands in your Dart/Flutter application without the risk of overlapping responses. This method helps create more reliable BLE communication in your apps. Remember, the key takeaway is to always wait for the expected response before proceeding to the next command for seamless functionality.

With this understanding, you can now handle intricate communication protocols in your applications with confidence—ensuring every command is executed in the proper sequence.