Question

I have an EditText in application. When I press space key twice through soft keyboard, a period should be inserted in that EditText.

How can I do that?

Answer 1

addTextChangedListener to your EditText. And override afterTextChanged() method for it.
Now check " " (Double space) in that text of Edittext, if it contains just replace it with "."

Something like,

final EditText edit = (EditText) findViewById(R.id.editText);
edit.addTextChangedListener(new TextWatcher()
{
 @Override
 public void afterTextChanged(Editable editable)
 {
    if (editable.toString().contains("  "))
    {
     edit.setText(ed.getText().toString().trim());
     edit.append(".");
    }
 }
});