[WebMethod]
    public bool Login(string account,string password)
    {
        if ("larrylee" == account & "123456" == password)
            return true;
        else
            return false;
    }

package com.mtk.lc.LoginDemo;

import java.util.ArrayList;
import java.util.List;

import org.apache.http.NameValuePair;
import org.apache.http.message.BasicNameValuePair;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class LoginDemo extends Activity {
    EditText editTextAccount;
    EditText editTextPsw;
    Button buttonLogin;
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        editTextAccount=(EditText) findViewById(R.id.editTextAccount);
        editTextPsw=(EditText) findViewById(R.id.editTextPsw);
        buttonLogin=(Button) findViewById(R.id.buttonLogin);
        buttonLogin.setOnClickListener(new View.OnClickListener() {
            
            @Override
            public void onClick(View v) {
                List<NameValuePair> params=new ArrayList<NameValuePair>();
                params.add(new BasicNameValuePair("account", editTextAccount.getText().toString()));//傳遞參數
                params.add(new BasicNameValuePair("password", editTextPsw.getText().toString()));//傳遞參數
                HTTPThread httpThread=new HTTPThread(loginHandler);
                //在工作線程中執行耗時任務，防止UI線程阻塞
                httpThread.doStart("http://10.0.2.2:2161/WebSite1/Service.asmx/Login", params, LoginDemo.this);
                //10.0.2.2為電腦對于模擬器而言的IP地址。
            }
        });
    }
    private Handler loginHandler=new Handler(){
        public void handleMessage(Message message) {
            switch (message.what) {
            case 1://程序執行正常
                Boolean res=message.getData().getBoolean("login");
                if(res){//成功登陸
                    Toast.makeText(LoginDemo.this, "Successd!", Toast.LENGTH_LONG).show();
                }else{//登陸失敗
                    Toast.makeText(LoginDemo.this, "Fail!", Toast.LENGTH_LONG).show();
                }
                break;

            default://程序異常...（網絡連接出錯）
                Toast.makeText(LoginDemo.this, "Error!", Toast.LENGTH_LONG).show();
                break;
            }
        }
    };
    
}

package com.mtk.lc.LoginDemo;

import java.io.IOException;
import java.util.List;

import org.apache.http.NameValuePair;
import org.apache.http.ParseException;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.protocol.HTTP;
import org.apache.http.util.EntityUtils;

import android.app.ProgressDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;

public class HTTPThread extends Thread {
    ProgressDialog pdDialog = null;
    String urlString = null;
    List<NameValuePair> params = null;
    Handler handler = null;

    public HTTPThread(Handler handler) {
        this.handler = handler;
    }

    public void doStart(String urlString, List<NameValuePair> params,
            Context context) {//進行一些初始化工作然后調用start()讓線程運行
        this.urlString = urlString;
        this.params = params;
        pdDialog = new ProgressDialog(context);
        pdDialog.setTitle("Login...");
        pdDialog.setMessage("Connecting to Server...");
        pdDialog.setIndeterminate(true);
        pdDialog.setButton("Cancel", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int which) {
                pdDialog.cancel();
            }
        });
        pdDialog.show();
        this.start();
    }

    @Override
    public void run() {
        Message msg = new Message();
        Bundle data = new Bundle();
        try {
            boolean result = webServiceLogin();//執行網絡服務請求，耗時操作。。。
            msg.what=1;
            data.putBoolean("login", result);
            data.putString("info", "normal");
            msg.setData(data);
        } catch (ParseException e) {
            msg.what=2;
            data.putString("info", "Error");
            msg.setData(data);
            e.printStackTrace();
        } catch (ClientProtocolException e) {
            msg.what=2;
            data.putString("info", "Error");
            msg.setData(data);
            e.printStackTrace();
        } catch (IOException e) {
            msg.what=2;
            data.putString("info", "Error");
            msg.setData(data);
            e.printStackTrace();
        } finally {
            pdDialog.dismiss();
            handler.sendMessage(msg);
        }
    }

    private boolean webServiceLogin() throws ParseException,
            ClientProtocolException, IOException {
        HttpClient httpClient = new DefaultHttpClient();//HTTP客戶端，使用默認客戶端
        HttpPost httpPost = new HttpPost(urlString);//建立HttpPost對象
        httpPost.setEntity(new UrlEncodedFormEntity(params, HTTP.UTF_8));//設置參數
        String res = EntityUtils.toString(httpClient.execute(httpPost)
                .getEntity());//執行并返回結果：
        
//          <?xml version="1.0" encoding="utf-8" ?> 
//          <boolean xmlns="http://tempuri.org/">true</boolean> 
        
        if (res.contains("true")) {//偷個懶不對XML進行解析了，返回中有true就是登陸成功了。
            return true;
        }
        return false;
    }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="fill_parent"
    android:layout_height="fill_parent">
    <TextView android:id="@+id/textView1" android:layout_width="wrap_content"
        android:layout_height="wrap_content" android:text="Account:"
        android:textSize="10pt"></TextView>
    <EditText android:layout_height="wrap_content"
        android:layout_width="match_parent" android:id="@+id/editTextAccount"></EditText>
    <TextView android:id="@+id/textView2" android:layout_width="wrap_content"
        android:layout_height="wrap_content" android:textSize="10pt"
        android:text="Pass Word:"></TextView>
    <EditText android:layout_height="wrap_content"
        android:layout_width="match_parent" android:id="@+id/editTextPsw"
        android:password="true"></EditText>
    <Button android:layout_width="wrap_content"
        android:layout_height="wrap_content" android:id="@+id/buttonLogin"
        android:text="Login"></Button>
</LinearLayout>