Yes, using Timer() in Android can cause performance issues, and it is not ideal for UI updates. Here’s why and how to properly handle it.

Why Using Timer() Can Be a Problem in Android?

• Timer runs tasks on a separate thread but cannot update UI elements (like ProgressBar) directly.
• If you try to update UI elements from a TimerTask, you will get an error: "Only the original thread that created a view hierarchy can touch its views."
• If you use sleep() in the main thread (like time.sleep() in Python), it will freeze the UI, making the app feel laggy.

What is the Best Alternative?

• Instead of Timer(), use: ✅ Handler with postDelayed() (Recommended for simple periodic tasks)
• ✅ CountDownTimer (Best for progress bars & timers)
• ✅ ScheduledExecutorService (More flexible alternative to Timer)

Best Solutions for Your Use Case (Updating a ProgressBar)

1️⃣ Using Handler.postDelayed() (Recommended)

Java:

Handler handler = new Handler();
int progress = 0;

Runnable runnable = new Runnable() {
    @Override
    public void run() {
        if (progress <= 100) {
            progressBar.setProgress(progress);
            progress += 5;
            handler.postDelayed(this, 500);
        }
    }
};
handler.post(runnable);

Kotlin:

val handler = Handler(Looper.getMainLooper()) 
var progress = 0

val runnable = object : Runnable {
    override fun run() {
        if (progress <= 100) {
            progressBar.progress = progress
            progress += 5
            handler.postDelayed(this, 500)
        }
    }
}

handler.post(runnable)

2️⃣ Using CountDownTimer (Best for a Timed Progress Bar)

Java

new CountDownTimer(10000, 500) { // Total 10 sec, tick every 500ms
    public void onTick(long millisUntilFinished) {
        int progress = (int) ((10000 - millisUntilFinished) / 100);
        progressBar.setProgress(progress);
    }

    public void onFinish() {
        progressBar.setProgress(100);
    }
}.start();

Kotlin

object : CountDownTimer(10000, 500) {
    override fun onTick(millisUntilFinished: Long) {
        val progress = ((10000 - millisUntilFinished) / 100).toInt()
        progressBar.progress = progress
    }

    override fun onFinish() {
        progressBar.progress = 100
    }
}.start()

3️⃣ Using ScheduledExecutorService (Better than Timer)

Java:

ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);
scheduler.scheduleAtFixedRate(new Runnable() {
    @Override
    public void run() {
        runOnUiThread(() -> {
            if (progress <= 100) {
                progressBar.setProgress(progress);
                progress += 5;
            }
        });
    }
}, 0, 500, TimeUnit.MILLISECONDS);

Kotlin:

val scheduler = Executors.newScheduledThreadPool(1)
var progress = 0

scheduler.scheduleAtFixedRate({
    runOnUiThread {
        if (progress <= 100) {
            progressBar.progress = progress
            progress += 5
        }
    }
}, 0, 500, TimeUnit.MILLISECONDS)

4️⃣ Using Coroutine & delay() (Recommended for Modern Kotlin)

import kotlinx.coroutines.*

var progress = 0

fun startProgressBar() {
    GlobalScope.launch(Dispatchers.Main) {
        while (progress <= 100) {
            progressBar.progress = progress
            progress += 5
            delay(500L)
        }
    }
}

Conclusion

❌ Timer() is not ideal because it runs on a background thread, making UI updates problematic.

✅ Instead, use:

• Handler.postDelayed() for simple repeated UI updates.
• CountDownTimer for fixed-time progress bars.
• ScheduledExecutorService for background tasks.