先寫好登入介面的佈局，記住要寫一個Checkbox。

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="請輸入賬號" />
    <EditText 
        android:id="@+id/ed_zhanghao"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="請輸入密碼" />
    <EditText 
        android:id="@+id/ed_mima"
        android:inputType="textPassword"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>
    <RelativeLayout 
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
        <CheckBox 
            android:id="@+id/cb"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:checked="true"
            android:text="記住密碼"/>
        <Button 
            android:onClick="denglu"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentRight="true"
            android:text="登入"/>
    </RelativeLayout>

</LinearLayout>
 

再寫一個儲存賬號密碼的工具類，儲存路勁可以寫在手機或者SD卡里：

package com.xh.tx.denglu.service;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.HashMap;
import java.util.Map;

import android.content.Context;
import android.os.Environment;

public class Servicein {
	public static boolean serviceinfo(Context context,String zhanghao,String mima){
		
		try {
			//File f= new File("data/data/com.xh.tx.denglu/info.txt");
			//context.getFilesDir();幫助我們返回一個目錄，data/data/包名/files/
			//context.getCacheDir();這個是快取目錄
			//Environment.getExternalStorageState();獲取SD卡是什麼樣的狀態
			//String s=Environment.MEDIA_MOUNTED;獲取SD卡的插入狀態
			//Environment.getExternalStorageDirectory();返回一個SD卡的路勁；
			File f= new File(context.getFilesDir(),"info.txt");
			FileOutputStream fs=new FileOutputStream(f);
			fs.write((zhanghao+"#####"+mima).getBytes());
			fs.close();
			return true;
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
			return false;
		}	
	}
	public static Map<String,String> getinfo(Context context){
		File f= new File(context.getFilesDir(),"info.txt");
		try {
		BufferedReader br= new BufferedReader(new InputStreamReader(new FileInputStream(f)));
		String s=br.readLine();
		String[] srinfo=s.split("#####");
		Map<String,String> map=new HashMap<String, String>();
		map.put("zhanghao",srinfo[0]);
		map.put("mima",srinfo[1]);
		return map;
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
			return null;
		}
		
		
	}
}
 

package com.xh.tx.denglu;

import java.util.Map;

import com.xh.tx.denglu.service.Servicein;

import android.os.Bundle;
import android.app.Activity;
import android.app.Service;
import android.text.TextUtils;
import android.view.Menu;
import android.view.View;
import android.widget.CheckBox;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends Activity {
	 private EditText ed_zhanghao;
	 private EditText ed_mima;
	 private CheckBox cb;
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		ed_zhanghao = (EditText) findViewById(R.id.ed_zhanghao);
		ed_mima = (EditText) findViewById(R.id.ed_mima);
		cb = (CheckBox) findViewById(R.id.cb);
		//檢查是否有賬號密碼，如果有，需要回顯
		Map<String, String> map=Servicein.getinfo(this);
		if(map!=null){
			ed_zhanghao.setText(map.get("zhanghao"));
			ed_mima.setText(map.get("mima"));
		}
	}

	public void denglu(View v){
		String zhanghao = ed_zhanghao.getText().toString().trim();
		String mima = ed_mima.getText().toString().trim();
		if(TextUtils.isEmpty(zhanghao)||TextUtils.isEmpty(mima)){
			Toast.makeText(this, "賬號或者密碼不能為空", Toast.LENGTH_SHORT).show();
		}else{
			if(cb.isChecked()){
				boolean result=Servicein.serviceinfo(this,zhanghao,mima);
				if(result){
					Toast.makeText(this, "儲存成功", Toast.LENGTH_SHORT).show();
				}
			}
			if("zhangsan".equals(zhanghao)&&"123456".equals(mima)){
				Toast.makeText(this, "登陸成功", Toast.LENGTH_SHORT).show();
			}else{
				Toast.makeText(this, "登入失敗", Toast.LENGTH_SHORT).show();
			}
		}

	}

}