How to Safely Access TextView in Android from a Runnable Thread

Описание: Discover how to handle UI updates in Android applications safely when dealing with `Runnable` threads to prevent application freezes.
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This video is based on the question https://stackoverflow.com/q/72104797/ asked by the user 'Doublementi' ( https://stackoverflow.com/u/18830542/ ) and on the answer https://stackoverflow.com/a/72108513/ provided by the user 'Isuru udayanga' ( https://stackoverflow.com/u/18056715/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Safely Access TextView in Android from a Runnable Thread

When developing Android applications, you might face issues when trying to update UI elements such as TextView from a separate thread. This is a common problem that many developers encounter, particularly when implementing multithreading for tasks like battery measurement or data processing. If your application freezes or crashes when attempting to access UI components from a Runnable thread, you've come to the right place. In this post, we'll explore the problem and provide you with a simple solution to ensure your app runs smoothly.

Understanding the Problem

In the provided code snippet, the developer faces an issue when trying to update a TextView that displays the battery percentage. The update occurs in a custom Runnable class (e.g., ExampleRunnable) which is created and started as a separate thread. The critical part is that UI components in Android must be manipulated from the main thread (also known as the UI thread). If you try to update your TextView—or any other UI component—from a background thread, you'll encounter unexpected behavior, such as application freezes or crashes.

Example Scenario

Let's analyze the relevant part of the code where the issue arises:

[[See Video to Reveal this Text or Code Snippet]]

In this snippet, an attempt to update the TextView is made directly from the Runnable thread, which is not allowed. As a result, the app may become unresponsive or even crash.

The Solution

To address this issue, Android provides a simple method to perform UI updates from background threads. You can use the runOnUiThread() method, which allows you to execute a block of code on the main (UI) thread safely. Here's how you can implement it:

Step-by-Step Implementation

Wrap Your UI Code in runOnUiThread: Replace your existing TextView updates with the following code snippet when you need to change the UI from your Runnable.

[[See Video to Reveal this Text or Code Snippet]]

Usage in Fragments: If your code is within a Fragment, you should use the following syntax to ensure you're calling the UI updates correctly:

[[See Video to Reveal this Text or Code Snippet]]

Why It Works

The runOnUiThread method essentially queues the provided action to be executed on the main thread. By doing this, you ensure that any code meant to interact with the UI will run safely, avoiding issues related to multithreading. It's a crucial technique for any Android developer to keep in mind when working on complex applications involving background operations.

Conclusion

Accessing and updating TextView components from a background thread can lead to significant issues, including freezes or crashes. However, by using the runOnUiThread() method, you can safely manipulate UI components from your background tasks. Always remember to handle UI updates within the main thread to keep your application responsive and functioning as intended.

By following this guide, you can tackle one of the common pitfalls in Android development. Happy coding!