here is my code
 i try his solution but it didnt work
   package com.FF_studio.psp_rd_lite_1;
    import android.app.Activity;
    import android.os.Bundle;
    import android.view.Menu;
    import android.view.MenuItem;
    import android.view.View;
    import android.widget.EditText;
    import android.widget.Toast;
    public class LoginActivity extends Activity {
        EditText urn,pwd;
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_login);
        }
        public void login(View v) {
            urn = (EditText)findViewById(R.id.username);
            pwd = (EditText)findViewById(R.id.password);
            String site = "";
            String error = "用戶名稱或密碼錯誤,請重新輸入";
            String url = "";
            String ans = "admin";
            String ans1 = "rico1010";
            urn.getText().toString();
            pwd.getText().toString();
            if(urn = ans) //error occur here
               url = "";
            else
                Toast.makeText(this, error, Toast.LENGTH_SHORT).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.login, menu);
            return true;
        }
        @Override
        public boolean onOptionsItemSelected(MenuItem item) {
            // Handle action bar item clicks here. The action bar will
            // automatically handle clicks on the Home/Up button, so long
            // as you specify a parent activity in AndroidManifest.xml.
            int id = item.getItemId();
            if (id == R.id.action_settings) {
                return true;
            }
            return super.onOptionsItemSelected(item);
        }
        }
 
     
     
    