Handler - schedule periodic tasks in Android

!!readme.md

Handler - Stub

Use a Handler to run code on a given thread after a delay or repeat tasks periodically on a thread.

1. constructing a Handler and then
2. "posting" Runnable code to the event message queue on the thread to be processed

Handler can communicate with UI-thread

handler.post(); handler.postAtFrontOfQueue(); handler.postDelayed(); handler.postAtTime();

exec_after_Delay.java

// We need to use this Handler package
import android.os.Handler;

// 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");
    }
};
// Run the above code block on the main thread after 2 seconds
handler.postDelayed(runnableCode, 2000);

exec_repetedly_at_an_interval.java

// We need to use this Handler package
import android.os.Handler;

// 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
      // 'this' is referencing the Runnable object
      handler.postDelayed(this, 2000);
    }
};
// Start the initial runnable task by posting through the handler
handler.post(runnableCode);