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

The simple fix to your example is :

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

Or we can use normal thread for example (with original Runner) :

Thread thread = new Thread() {    @Override    public void run() {        try {            while(true) {                sleep(1000);                handler.post(this);            }        } catch (InterruptedException e) {            e.printStackTrace();        }    }};thread.start();

You may consider your runnable object just as a command that can be sent to the message queue for execution, and handler as just a helper object used to send that command.

More details are here http://developer.android.com/reference/android/os/Handler.html

new Handler().postDelayed(new Runnable() {    public void run() {        // do something...                  }}, 100);

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");}