保存数据到手机sd卡(QQ登录保存密码)

记住:

getFilesDir()方法是获取手机内存的路径 /data/data/包名/files   自动建立一个files文件夹

Environment.getExternalStorageDirectory获取的是sd卡的路径， 自动获取  /mnt/card   不同的手机的路径可能有差异,所以要用 Environment获取/mnt...../card 

       Environment.getDataDirectory();  获取的手机内存的根路径:   /data

        //判断当前的手机是否有sd卡
String state = Environment.getExternalStorageState();
if(!Environment.MEDIA_MOUNTED.equals(state)){
//已经挂载
} 

package com.itheima28.qqlogin;import java.io.File;import java.util.Map;import com.itheima28.qqlogin.utils.Utils;import com.itheima28.qqlogin.utils.UtilsOfSDCard;import com.itheima28.qqlogin.R;import android.app.Activity;import android.os.Bundle;import android.text.TextUtils;import android.util.Log;import android.view.Menu;import android.view.MenuItem;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import android.widget.CheckBox;import android.widget.EditText;import android.widget.Toast;public class MainActivity extends Activity implements OnClickListener {private static final String TAG = "MainActivity";private EditText etNumber;private EditText etPassword;private CheckBox cbRemerberPWD;private Map<String, String> userInfoMap;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);//  /data/data/包名/files/*this.getFilesDir-- /data/data/com.itheima28.qqlogin/files */File file = this.getFilesDir();System.out.println(file.toString());etNumber = (EditText) findViewById(R.id.et_number);etPassword = (EditText) findViewById(R.id.et_password);  cbRemerberPWD = (CheckBox) findViewById(R.id.cb_remember_pwd);Button btnLogin = (Button) findViewById(R.id.btn_login);btnLogin.setOnClickListener(this);//回显userInfoMap = UtilsOfSDCard.getUserInfo(this);if(userInfoMap != null){etNumber.setText(userInfoMap.get("number"));etPassword.setText(userInfoMap.get("password"));} }@Overridepublic void onClick(View v) {//执行登录的方法//1.取出号码和密码String number = etNumber.getText().toString();String password = etPassword.getText().toString();if(TextUtils.isEmpty(number)||TextUtils.isEmpty(password)){//Toast--弹出吐司,下面的业务就不执行了Toast.makeText(this, "请正确输入", Toast.LENGTH_SHORT).show();/* 第一个参数为Context对象,MainActivity继承Context,所以用this就行了第二个参数时候提示的信息第三个参数持续的时间   Toast.LENGTH_SHORT--0秒    Toast.LENGTH_LONG--1秒 */}//2.判断记住密码是否被选中,如果被选中,存起来if(cbRemerberPWD.isChecked()){//当前需要记住密码Log.i(TAG, "记住密码："+number + ","+password);boolean isSuccess = UtilsOfSDCard.saveUserInfo(this,number, password);if(isSuccess){ Toast.makeText(this, "保存成功", Toast.LENGTH_SHORT).show();}else{ Toast.makeText(this, "保存失败", Toast.LENGTH_SHORT).show();}} //3.登录成功Toast.makeText(this, "登录成功", Toast.LENGTH_SHORT).show();}/* * 4.0以后的问题  读sc卡不加权限出现的问题:  W/System.err(6323): java.io.FileNotFoundException: /mnt/sdcard/ithema28.txt: open failed: EACCES (Permission denied)需要加读写权限 */}

package com.itheima28.qqlogin.utils;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.content.Context;import android.os.Environment;import android.text.TextUtils;public class UtilsOfSDCard {/** * 保存用户信息到sd卡 * */public static boolean saveUserInfo(Context context,String number,String password){ try {//判断当前的手机是否有sd卡String state = Environment.getExternalStorageState();if(!Environment.MEDIA_MOUNTED.equals(state)){//已经挂载} /*   自动获取  /mnt/card   不同的手机的路径可能有差异,所以要用 Environment获取/mnt...../card  * */File sdCardFile = Environment.getExternalStorageDirectory();File file = new File(sdCardFile, "ithema28.txt");//指定存储的文件名字FileOutputStream fos = new FileOutputStream(file);String data = number + "##" + password;fos.write(data.getBytes());fos.flush();return true;} catch (Exception e) {e.printStackTrace();}return false;}/** *  到sd卡获取用户信息 * */ public static Map<String,String> getUserInfo(Context context){  try { //判断当前的手机是否有sd卡String state = Environment.getExternalStorageState();if(!Environment.MEDIA_MOUNTED.equals(state)){//已经挂载}  File sdCardFile = Environment.getExternalStorageDirectory();File file = new File(sdCardFile, "ithema28.txt");//指定存储的文件名字BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream(file)));String text = br.readLine(); if(!TextUtils.isEmpty(text)){Map<String,String> userInfoMap = new HashMap<String,String>();String[] split = text.split("##");userInfoMap.put("number", split[0]);userInfoMap.put("password", split[1]);} } catch (Exception e) {}return null;}}

<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" >    <EditText         android:id="@+id/et_number"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:hint="请输入QQ号"        />     <EditText         android:id="@+id/et_password"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:inputType="textPassword"        android:hint="请输入密码"/>         <CheckBox          android:id="@+id/cb_remember_pwd"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:checked="true"         android:text="记住密码"/>     <!-- checkedtrue代表选中 -->            <Button          android:id="@+id/btn_login"         android:layout_height="wrap_content"         android:layout_width="wrap_content"         android:text="登录"/></LinearLayout>