android 中在内存中保存文件

以一个登陆的例子来将，将登陆时的信息保存在指定目录的文件中。在第一次登陆后，对用户名等在内存文件中保存。

android界面：

 

界面：

<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"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="@string/PlaseInputName" 
        android:textSize="20dp"
        />

    <EditText
        android:id="@+id/et_username"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_marginBottom="20dp" 
        android:textColor="#FFFF00"
        />

    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="@string/PlaseInputPwd"
        android:textSize="20dp" />

    <EditText
        android:inputType="textPassword"
        android:id="@+id/et_userpwd"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" />

    <RelativeLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" >

        <CheckBox
            android:id="@+id/cb_remeber_pwd"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:checked="true"
            android:text="@string/checkpwd" />

        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" 
            android:layout_alignParentRight="true"
            android:onClick="login"
            android:text="@string/login"
            />
    </RelativeLayout>

</LinearLayout>

界面原型：

 

在第一次登陆时，看是否选择记住密码，如果是将登陆信息保存后读取

public class LoginService {
    public static boolean saveUerInfo(Context context, String UerName,
            String password) {

        try {
            File file = new File(context.getFilesDir(), "info.txt");
            // File file = new File("/data/data/com.example.login/info.txt");
            FileOutputStream fos = new FileOutputStream(file);
            fos.write((UerName + "###" + password).getBytes());
            return true;
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            return false;
        }

    }

主函数：

package com.example.login;

import java.util.Map;

import com.example.login.service.LoginService;

import android.os.Bundle;
import android.app.Activity;
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 et_username;
    private EditText et_userpwd;
    private CheckBox cb;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        et_username = (EditText) this.findViewById(R.id.et_username);
        et_userpwd = (EditText) this.findViewById(R.id.et_userpwd);
        cb = (CheckBox) this.findViewById(R.id.cb_remeber_pwd);
        Map<String, String> map = LoginService.getSaveUserInfo(this);
        if(map!=null){
            et_username.setText(map.get("name"));
            et_userpwd.setText(map.get("password"));
        }
    }

    // 登陆
    public void login(View view) {
        String name = et_username.getText().toString().trim();
        String password = et_userpwd.getText().toString().trim();
        if (TextUtils.isEmpty(name) || (TextUtils.isEmpty(password))) {
            Toast.makeText(this, "用户名或密码不能为空", Toast.LENGTH_SHORT).show();
        } else {
            // 登陆
            if (cb.isChecked()) {
                // 保存密码
                boolean result = LoginService.saveUerInfo(this, name, password);
                if (result) {
                    Toast.makeText(this, "保存信息成功", 0).show();
                }
            }
            // 登陆
            if ("zhangsan".equals(name) && ("12345").equals(password)) {
                Toast.makeText(this, "登陆成功", 0).show();
            } else {
                Toast.makeText(this, "登陆失败", 0).show();
            }
        }
    }

    public EditText getEt_username() {
        return et_username;
    }

    public void setEt_username(EditText et_username) {
        this.et_username = et_username;
    }

    public EditText getEt_userpwd() {
        return et_userpwd;
    }

    public void setEt_userpwd(EditText et_userpwd) {
        this.et_userpwd = et_userpwd;
    }

    public CheckBox getCb() {
        return cb;
    }

    public void setCb(CheckBox cb) {
        this.cb = cb;
    }

}

方法：

package com.example.login.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 org.apache.http.entity.InputStreamEntity;

import android.content.Context;

public class LoginService {
    public static boolean saveUerInfo(Context context, String UerName,
            String password) {

        try {
            File file = new File(context.getFilesDir(), "info.txt");
            // File file = new File("/data/data/com.example.login/info.txt");
            FileOutputStream fos = new FileOutputStream(file);
            fos.write((UerName + "###" + password).getBytes());
            return true;
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            return false;
        }

    }

    public static Map<String, String> getSaveUserInfo(Context context) {
        try {
            File file = new File(context.getFilesDir(), "info.txt");
            FileInputStream fis = new FileInputStream(file);
            BufferedReader br = new BufferedReader(new InputStreamReader(fis));
            String str = br.readLine();
            String[] infos = str.split("###");
            Map<String, String> map = new HashMap<String, String>();
            map.put("name", infos[0]);
            map.put("password", infos[1]);
            return map;
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return null;


    }
}