how to change the focus from one edittext to another

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Mobile

Android

i have 2 edittext in my form design. what i want to acheive is that in the first edittext after typing few characters say for example i type "abc", the focus should automatically shift to the next edittext
i used the following code but cant get it right

gtin=(EditText) findViewById(R.id.editText1);
		expiry=(EditText) findViewById(R.id.editText2);
		String sgtin=gtin.getText().toString();
		if(sgtin.length()==3){
			expiry.findFocus();
			//expiry.requestFocus();
		}