android___文件访问权限

<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="com.example.login.MainActivity" >

<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/user" />

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

<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/password" />

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

<RadioGroup
android:id="@+id/radioGroup"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal"
>

<RadioButton
android:id="@+id/rd_private"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:checked="true"
android:text="私有" />

<RadioButton
android:id="@+id/rd_readable"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="可读" />

<RadioButton
android:id="@+id/rd_writeable"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="可写" />

<RadioButton
android:id="@+id/rd_rewrable"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="公开" />
</RadioGroup>

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

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

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

</LinearLayout>

package com.example.login;

import java.util.Map;

import android.app.Activity;
import android.os.Bundle;
import android.text.TextUtils;
import android.util.Log;
import android.view.View;
import android.widget.CheckBox;
import android.widget.EditText;
import android.widget.RadioGroup;
import android.widget.Toast;

import com.example.login.service.LoginService;

public class MainActivity extends Activity {

private static final String tag = "MainActivity";
private EditText et_username;
private EditText et_password;
private CheckBox cb;
private RadioGroup rg;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

et_username = (EditText) this.findViewById(R.id.et_username);
et_password = (EditText) this.findViewById(R.id.et_password);
cb = (CheckBox) this.findViewById(R.id.cb_remember_pwd);

rg = (RadioGroup) this.findViewById(R.id.radioGroup);

}

// 登陆控件
public void login(View view) {

String name = et_username.getText().toString().trim();
String pass = et_password.getText().toString().trim();

if (TextUtils.isEmpty(name) || TextUtils.isEmpty(pass)) {
Toast.makeText(this, "用户名或密码不能为空", Toast.LENGTH_SHORT).show();
return;
} else {

// 判断是否保存密码
if (cb.isChecked()) {
// 保存用户和密码
Log.i(tag, "需要保存用户名和密码");

boolean result = false;

//返回被选中的id
int id = rg.getCheckedRadioButtonId();

switch (id) {
case R.id.rd_private:
LoginService.saveUserInfo(this,name, pass,1);
break;
case R.id.rd_readable:
LoginService.saveUserInfo(this,name, pass,2);
break;

case R.id.rd_writeable:
LoginService.saveUserInfo(this,name, pass,3);
break;

case R.id.rd_rewrable:
LoginService.saveUserInfo(this,name, pass,4);
break;
}

if(result){
Toast.makeText(this, "用户名和密码保存成功", Toast.LENGTH_SHORT).show();
}
}

// 登陆 发送信息到服务器，服务喊叫验证是否正确
if ("zhangsan".equals(name) && "123".equals(pass)) {
Toast.makeText(this, "登陆成功", 0).show();
} else {
Toast.makeText(this, "用户名或密码错误", Toast.LENGTH_SHORT).show();
}
}
}
}

package com.example.login.service;

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

import android.annotation.SuppressLint;
import android.content.Context;

/*
*
* 登录服务
*
*
*
* **/
@SuppressLint("WorldReadableFiles")
public class LoginService {

/**
*  传入一个上下文：Context
*  保存用户名和密码的方法
*
*  return
*      true:成功
*      false:失败
*
*  mode:
*      1:私有
*      2:可读
*      3:可写
*      4:公开
*
* */
public static  boolean saveUserInfo(Context context ,String username,String password,int mode){

FileOutputStream fos  = null;

try{

/**
*  Context.MODE_PRIVATE：私有的方法创建文件
*
*
*
* */

switch (mode) {
case 1:
fos = context.openFileOutput("private.txt", Context.MODE_PRIVATE);
break;
case 2:
fos = context.openFileOutput("readable.txt", Context.MODE_WORLD_READABLE);
break;
case 3:
fos = context.openFileOutput("writeable.txt", Context.MODE_WORLD_WRITEABLE);
break;
case 4:
fos = context.openFileOutput("public.txt", Context.MODE_WORLD_READABLE+Context.MODE_WORLD_WRITEABLE);
break;
}

//zhangsan###123
fos.write((username+"###"+password).getBytes());

fos.close();

return true;
}catch(Exception e){

return false;
}

}

}