Question

new AlertDialog.Builder(this)
  .setMessage(mymessage)
  .setTitle(title)
  .setCancelable(true)
  .setNeutralButton(android.R.string.cancel,
     new DialogInterface.OnClickListener() {
     public void onClick(DialogInterface dialog, int whichButton){}
     })
  .show();

Hi, could someone explain what this java language feature is called, to be able to call methods without directly specifying the object before the ‘.’ ?

I would like to read more about how to use this…

and does it only work with “new” or can I use existing objects with this syntax?

Answer 1

The line of code is terminated by the semicolon. What you have there is (formatting-aside) identical to:

new AlertDialog.Builder(this).setMessage(mymessage).setTitle(title).setCancelable(true).setNeutralButton(android.R.string.cancel, new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int whichButton){}}).show();

I think you’ll agree that the linebreaks make it more readable!

Now, each one of those methods in the chain is implemented as returning this as a useful “side effect” (in the intent sense, rather than functional sense) – this means that myBuilder.setMessage(myMessage) returns the modified myBuilder, which you’re then free to use .setTitle(title) on, et cetera.