editText field is required before moving on to another Activity

It's easy...check if your EditText is empty as in below example below.

if( TextUtils.isEmpty(userName.getText())){   /**    *   You can Toast a message here that the Username is Empty        **/   userName.setError( "First name is required!" );}else{   Intent i = new Intent(getApplicationContext(), Login.class);   startActivity(i);}

Try this:

bt.setOnClickListener(new OnClickListener() {    public void onClick(View arg0)    {        String  str=et.getText().toString();        if(str.equalsIgnoreCase(""))        {            et.setHint("please enter username");//it gives user to hint            et.setError("please enter username");//it gives user to info message //use any one //        }        else        {            Intent in=new Intent(getApplicationContext(),second.class);            startActivity(in);        }    }});

You can also try this:

 if ( ( userName.getText().toString().trim().equals("")) )  {      Toast.makeText(getApplicationContext(), "User name is empty", Toast.LENGTH_SHORT).show(); } else {      Intent i = new Intent(getApplicationContext(), Login.class);      startActivity(i); }