Question

Given a TextView widget named secondsTextView and a Runnable object named updateSeconds, which statement updates the widget on the UI thread?

Answer 1

To update the secondsTextView widget on the UI thread using the updateSeconds Runnable object, use the following statement: `secondsTextView.post(updateSeconds);`

Step-by-step explanation:

In Android, modifications to UI widgets should occur on the main (UI) thread to avoid potential conflicts and ensure a smooth user experience. The `TextView` widget named `secondsTextView` needs updating, and the `Runnable` object named `updateSeconds` is intended to perform this action. Utilizing the `post()` method associated with the `TextView`, the `updateSeconds` `Runnable` is posted to the UI thread's message queue, ensuring that the updates to the `secondsTextView` occur on the UI thread.

The `post()` method enqueues the `Runnable` onto the UI thread's message queue, allowing it to execute at an appropriate time, typically after other pending UI operations have completed. This way, it prevents potential concurrency issues that might arise when directly manipulating UI elements from background threads.

Using `secondsTextView.post(updateSeconds)` adheres to Android's threading model, guaranteeing that updates to the `TextView` are executed safely and correctly on the UI thread.