从php到android获取变量的内容，并使用Toast类进行显示

我想从php到android获取变量的内容，并使用Toast类进行显示。我写了以下代码，如果其中一个或两个字段都为空，register.php文件将打印$isEmpty，我的java代码应该获得$isEmpty变量的内容，if(text == "isEmpty")作为结果Toast类应该显示R.string.empty。但是我使用以下代码的程序无法使用Toast类显示R.string.empty。

public class MainActivity extends Activity {
    EditText username, password;
    Button register;
  String name, pass;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    username = (EditText) findViewById(R.id.editText);
        password= (EditText) findViewById(R.id.editText2);
        register= (Button) findViewById(R.id.register);
        register.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                try{
                    // CALL GetText method to make post method call
                    GetText();
                }
                catch(Exception ex)
                {
                }
            }
        });
    }
    public  void  GetText()  throws UnsupportedEncodingException
    {
        // Get user defined values
        name = username.getText().toString();
        pass   = password.getText().toString();

        // Create data variable for sent values to server
        String data = URLEncoder.encode("username", "UTF-8")
                + "=" + URLEncoder.encode(name, "UTF-8");
        data += "&" + URLEncoder.encode("password", "UTF-8") + "="
                + URLEncoder.encode(pass, "UTF-8");
        String text = "";
        BufferedReader reader=null;
        // Send data
        try
        {
            // Defined URL  where to send data
            URL url = new URL("http://127.0.0.1:8080/apps/register.php");
            // Send POST data request
            URLConnection conn = url.openConnection();
            conn.setDoOutput(true);
            OutputStreamWriter wr = new OutputStreamWriter(conn.getOutputStream());
            wr.write( data );
            wr.flush();
            // Get the server response
            reader = new BufferedReader(new InputStreamReader(conn.getInputStream()));
            StringBuilder sb = new StringBuilder();
            String line = null;
            // Read Server Response
            while((line = reader.readLine()) != null)
            {
                // Append server response in string
                sb.append(line + "'n");
            }

            text = sb.toString();
        }
        catch(Exception ex)
        {
        }
        finally
        {
            try
            {
                reader.close();
            }
            catch(Exception ex) {}
        }
        // Show response on activity
        if(text == "isEmpty")
        { String isEmpty = (String)getText(R.string.empty);
            Toast.makeText(getApplicationContext(), isEmpty, Toast.LENGTH_LONG).show(); }
    }
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }}

和

 <?php
if($_SERVER["REQUEST_METHOD"] == "POST") {
 $username = urldecode($_POST['username']);
$login = urldecode($_POST['login']);
if(empty($username) || empty($login)) {
        $isEmpty = "isEmpty";
print "$isEmpty";
}
}?>