How Does `runOnUiThread()` Ensure Smooth UI Updates in Android?

The Proper Usage of runOnUiThread in Android: A Detailed Explanation

In Android development, interacting with the UI thread can be a crucial aspect of ensuring smooth and responsive user experiences. runOnUiThread() is a key method for achieving this interaction.

Understanding the Problem: Unresponsive Button Click

In the code snippet provided, an issue arises after clicking the button. The button becomes unresponsive due to a misunderstanding of the runThread() method.

The Correct Implementation: Updating the UI Thread

To resolve the issue, it's necessary to rectify the implementation of runThread(). Instead of creating a new Thread directly within runThread(), a separate Thread object should be created and started. Within this new Thread's run() method, the UI thread updates should be performed using the runOnUiThread() method.

Corrected runThread() Method

private void runThread() {

    new Thread() {
        public void run() {
            while (i++ < 1000) {
                try {
                    runOnUiThread(new Runnable() {

                        @Override
                        public void run() {
                            btn.setText("#" + i);
                        }
                    });
                    Thread.sleep(300);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }.start();
}

Explanation of Corrections

1. Separate Thread Creation: The new Thread() block ensures that the UI thread is not blocked by the loop.
2. UI Updates via runOnUiThread: The UI updates (setting the button text) are now performed within a Runnable object passed to runOnUiThread(). This ensures that updates are made on the UI thread.
3. Sleep on the New Thread: Thread.sleep() is called on the new Thread, allowing the UI thread to remain responsive.

With these corrections, the button click will no longer result in app unresponsiveness, and the UI will update smoothly.

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