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android – Timertask or Handler

Posted by: admin March 11, 2020 Leave a comment

Questions:

Let’s say that I want to perform some action every 10 seconds and it doesn’t necessarily need to update the view.

The question is: is it better (I mean more efficient and effective) to use timer with timertask like here:

final Handler handler = new Handler();

TimerTask timertask = new TimerTask() {
    @Override
    public void run() {
        handler.post(new Runnable() {
            public void run() {
               <some task>
            }
        });
    }
};
timer = new Timer();
timer.schedule(timertask, 0, 15000);
}

or just a handler with postdelayed

final Handler handler = new Handler(); 
final Runnable r = new Runnable()
{
    public void run() 
    {
        <some task>
    }
};
handler.postDelayed(r, 15000);

Also I would be grateful if you could explain when to use which approach and why one of them is more efficient than another (if it actually is).

How to&Answers:

Handler is better than TimerTask.

The Java TimerTask and the Android Handler both allow you to schedule delayed and repeated tasks on background threads. However, the literature overwhelmingly recommends using Handler over TimerTask in Android (see here, here, here, here, here, and here).

Some of reported problems with TimerTask include:

  • Can’t update the UI thread
  • Memory leaks
  • Unreliable (doesn’t always work)
  • Long running tasks can interfere with the next scheduled event

Example

The best source for all kinds of Android examples that I have seen is at Codepath. Here is a Handler example from there for a repeating task.

// Create the Handler object (on the main thread by default)
Handler handler = new Handler();
// Define the code block to be executed
private Runnable runnableCode = new Runnable() {
    @Override
    public void run() {
      // Do something here on the main thread
      Log.d("Handlers", "Called on main thread");
      // Repeat this the same runnable code block again another 2 seconds
      handler.postDelayed(runnableCode, 2000);
    }
};
// Start the initial runnable task by posting through the handler
handler.post(runnableCode);

Related

Answer:

There are some disadvantages of using Timer

It creates only single thread to execute the tasks and if a task takes
too long to run, other tasks suffer. It does not handle exceptions
thrown by tasks and thread just terminates, which affects other
scheduled tasks and they are never run

Copied from:

TimerTask vs Thread.sleep vs Handler postDelayed – most accurate to call function every N milliseconds?

Answer:

Kotlin version of accepted answer:

val handler = Handler()

val runnableCode = object : Runnable {
    override fun run() {
       Log.d("Handlers", "Called on main thread")
       handler.postDelayed(this, 2000)
    }
}

handler.post(runnableCode)