Check if EditText is empty.

I did something like this once;

EditText usernameEditText = (EditText) findViewById(R.id.editUsername);
sUsername = usernameEditText.getText().toString();
if (sUsername.matches("")) {
    Toast.makeText(this, "You did not enter a username", Toast.LENGTH_SHORT).show();
    return;
}

private boolean isEmpty(EditText etText) {
    if (etText.getText().toString().trim().length() > 0) 
        return false;

    return true;
}

OR As Per audrius

  private boolean isEmpty(EditText etText) {
        return etText.getText().toString().trim().length() == 0;
    }

If function return false means edittext is not empty and return true means edittext is empty...

For validating EditText use EditText#setError method for show error and for checking empty or null value use inbuilt android class TextUtils.isEmpty(strVar) which return true if strVar is null or zero length

EditText etUserName = (EditText) findViewById(R.id.txtUsername);
String strUserName = etUserName.getText().toString();

 if(TextUtils.isEmpty(strUserName)) {
    etUserName.setError("Your message");
    return;
 }