How to run a Runnable thread in Android at defined intervals?

Question

I developed an application to display some text at defined intervals in the Android emulator screen. I am using the Handler class. Here is a snippet from my cod

Answer 1

now in Kotlin you can run threads this way:

class SimpleRunnable: Runnable {
    public override fun run() {
        println("${Thread.currentThread()} has run.")
    }
}
fun main(args: Array<String>) {
    val thread = SimpleThread()
    thread.start() // Will output: Thread[Thread-0,5,main] has run.
    val runnable = SimpleRunnable()
    val thread1 = Thread(runnable)
    thread1.start() // Will output: Thread[Thread-1,5,main] has run
}

Answer 2

Handler handler=new Handler();
Runnable r = new Runnable(){
    public void run() {
        tv.append("Hello World");                       
        handler.postDelayed(r, 1000);
    }
}; 
handler.post(r);

Answer 3

Kotlin

private lateinit var runnable: Runnable
override fun onCreate(savedInstanceState: Bundle?) {
    val handler = Handler()
    runnable = Runnable {
        // do your work
        handler.postDelayed(runnable, 2000)
    }
    handler.postDelayed(runnable, 2000)
}

Java

Runnable runnable;
Handler handler;

@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
    handler = new Handler();
    runnable = new Runnable() {
        @Override
        public void run() {
            // do your work
            handler.postDelayed(this, 1000);
        }
    };
    handler.postDelayed(runnable, 1000);
}

Answer 4

I think can improve first solution of Alex2k8 for update correct each second

1.Original code:

public void run() {
    tv.append("Hello World");
    handler.postDelayed(this, 1000);
}

2.Analysis

• In above cost, assume tv.append("Hello Word") cost T milliseconds, after display 500 times delayed time is 500*T milliseconds
• It will increase delayed when run long time

3. Solution

To avoid that Just change order of postDelayed(), to avoid delayed:

public void run() {
    handler.postDelayed(this, 1000);
    tv.append("Hello World");
}

Answer 5

If I understand correctly the documentation of Handler.post() method:

Causes the Runnable r to be added to the message queue. The runnable will be run on the thread to which this handler is attached.

So examples provided by @alex2k8, even though are working correctly, are not the same. In case, where Handler.post() is used, no new threads are created. You just post Runnable to the thread with Handler to be executed by EDT. After that, EDT only executes Runnable.run(), nothing else.

Remember: Runnable != Thread.