Android（十二）android常用工具类。

1、SharedPreferences保存密码的文件

package com.itheima62.mobileguard.utils;

import android.content.Context;
import android.content.SharedPreferences;

public class SpTools {
    public static void putString(Context context,String key,String value){
        SharedPreferences sp = context.getSharedPreferences(MyConstants.SPFILE, Context.MODE_PRIVATE);
        sp.edit().putString(key, value).commit();//保存数据
    }

    public static String getString(Context context,String key,String defValue){
        SharedPreferences sp = context.getSharedPreferences(MyConstants.SPFILE, Context.MODE_PRIVATE);
        return sp.getString(key, defValue);
    }
}

2、MD5加密

package com.itheima62.mobileguard.activities;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class Md5Utils {
    public static String md5(String str){
        StringBuilder mess = new StringBuilder();
        try {
            //获取MD5加密器
            MessageDigest md = MessageDigest.getInstance("MD5");
            byte[] bytes = str.getBytes();
            byte[] digest = md.digest(bytes);

            for (byte b : digest){
                //把每个字节转成16进制数
                int d = b & 0xff;// 0x000000ff
                String hexString = Integer.toHexString(d);
                if (hexString.length() == 1) {//字节的高4位为0
                    hexString = "0" + hexString;
                }
                mess.append(hexString);//把每个字节对应的2位十六进制数当成字符串拼接一起

            }
        } catch (NoSuchAlgorithmException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return mess + "";
    }
}

MD5