如何在Android活动中实现'记住我'功能？

Question

我有一个用户名，密码和复选框（文本'记住我'旁边）。

我该如何实现记住我的功能来保存用户名和密码数据？

任何帮助，将不胜感激。

Answer 1

您可以save values associated with your application using Preferences。

定义一些静态存储偏好文件名和密钥，你要使用：

public static final String PREFS_NAME = "MyPrefsFile"; 
private static final String PREF_USERNAME = "username"; 
private static final String PREF_PASSWORD = "password"; 

你会然后保存用户名和密码如下：

getSharedPreferences(PREFS_NAME,MODE_PRIVATE) 
     .edit() 
     .putString(PREF_USERNAME, username) 
     .putString(PREF_PASSWORD, password) 
     .commit(); 

所以你会像这样找回它们：

SharedPreferences pref = getSharedPreferences(PREFS_NAME,MODE_PRIVATE); 
String username = pref.getString(PREF_USERNAME, null); 
String password = pref.getString(PREF_PASSWORD, null); 

if (username == null || password == null) { 
    //Prompt for username and password 
} 

或者，如果你不想命名一个pref erences文件，你可以只使用默认：

SharedPreferences pref = PreferenceManager.getDefaultSharedPreferences(this); 

Answer 2

应该指出的是，尽管公认的答案成功地存储和检索的凭证，它存储它们作为纯文本。

这意味着密码将很容易在固定电话上看到。如果您选择存储敏感信息，如应用程序中的密码使用SharedPreferences，那么作为雷托迈耶（在Android发展的关系技术主管）说：你应该在非常至少encrypt the password它写入磁盘之前。

下面是它存储在SharedPreferences之前加密用户信息的实现：

/* 
Copyright (C) 2012 Sveinung Kval Bakken, [email protected] 

Permission is hereby granted, free of charge, to any person obtaining 
a copy of this software and associated documentation files (the 
"Software"), to deal in the Software without restriction, including 
without limitation the rights to use, copy, modify, merge, publish, 
distribute, sublicense, and/or sell copies of the Software, and to 
permit persons to whom the Software is furnished to do so, subject to 
the following conditions: 

The above copyright notice and this permission notice shall be 
included in all copies or substantial portions of the Software. 

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE 
LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION 
OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION 
WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. 

*/ 

import java.io.UnsupportedEncodingException; 
import java.security.GeneralSecurityException; 
import java.security.InvalidAlgorithmParameterException; 
import java.security.InvalidKeyException; 
import java.security.MessageDigest; 
import java.security.NoSuchAlgorithmException; 

import javax.crypto.Cipher; 
import javax.crypto.spec.IvParameterSpec; 
import javax.crypto.spec.SecretKeySpec; 

import android.content.Context; 
import android.content.SharedPreferences; 
import android.util.Base64; 


public class SecurePreferences { 

    public static class SecurePreferencesException extends RuntimeException { 

     public SecurePreferencesException(Throwable e) { 
      super(e); 
     } 

    } 

    private static final String TRANSFORMATION = "AES/CBC/PKCS5Padding"; 
    private static final String KEY_TRANSFORMATION = "AES/ECB/PKCS5Padding"; 
    private static final String SECRET_KEY_HASH_TRANSFORMATION = "SHA-256"; 
    private static final String CHARSET = "UTF-8"; 

    private final boolean encryptKeys; 
    private final Cipher writer; 
    private final Cipher reader; 
    private final Cipher keyWriter; 
    private final SharedPreferences preferences; 

    /** 
    * This will initialize an instance of the SecurePreferences class 
    * @param context your current context. 
    * @param preferenceName name of preferences file (preferenceName.xml) 
    * @param secureKey the key used for encryption, finding a good key scheme is hard. 
    * Hardcoding your key in the application is bad, but better than plaintext preferences. Having the user enter the key upon application launch is a safe(r) alternative, but annoying to the user. 
    * @param encryptKeys settings this to false will only encrypt the values, 
    * true will encrypt both values and keys. Keys can contain a lot of information about 
    * the plaintext value of the value which can be used to decipher the value. 
    * @throws SecurePreferencesException 
    */ 
    public SecurePreferences(Context context, String preferenceName, String secureKey, boolean encryptKeys) throws SecurePreferencesException { 
     try { 
      this.writer = Cipher.getInstance(TRANSFORMATION); 
      this.reader = Cipher.getInstance(TRANSFORMATION); 
      this.keyWriter = Cipher.getInstance(KEY_TRANSFORMATION); 

      initCiphers(secureKey); 

      this.preferences = context.getSharedPreferences(preferenceName, Context.MODE_PRIVATE); 

      this.encryptKeys = encryptKeys; 
     } 
     catch (GeneralSecurityException e) { 
      throw new SecurePreferencesException(e); 
     } 
     catch (UnsupportedEncodingException e) { 
      throw new SecurePreferencesException(e); 
     } 
    } 

    protected void initCiphers(String secureKey) throws UnsupportedEncodingException, NoSuchAlgorithmException, InvalidKeyException, 
      InvalidAlgorithmParameterException { 
     IvParameterSpec ivSpec = getIv(); 
     SecretKeySpec secretKey = getSecretKey(secureKey); 

     writer.init(Cipher.ENCRYPT_MODE, secretKey, ivSpec); 
     reader.init(Cipher.DECRYPT_MODE, secretKey, ivSpec); 
     keyWriter.init(Cipher.ENCRYPT_MODE, secretKey); 
    } 

    protected IvParameterSpec getIv() { 
     byte[] iv = new byte[writer.getBlockSize()]; 
     System.arraycopy("fldsjfodasjifudslfjdsaofshaufihadsf".getBytes(), 0, iv, 0, writer.getBlockSize()); 
     return new IvParameterSpec(iv); 
    } 

    protected SecretKeySpec getSecretKey(String key) throws UnsupportedEncodingException, NoSuchAlgorithmException { 
     byte[] keyBytes = createKeyBytes(key); 
     return new SecretKeySpec(keyBytes, TRANSFORMATION); 
    } 

    protected byte[] createKeyBytes(String key) throws UnsupportedEncodingException, NoSuchAlgorithmException { 
     MessageDigest md = MessageDigest.getInstance(SECRET_KEY_HASH_TRANSFORMATION); 
     md.reset(); 
     byte[] keyBytes = md.digest(key.getBytes(CHARSET)); 
     return keyBytes; 
    } 

    public void put(String key, String value) { 
     if (value == null) { 
      preferences.edit().remove(toKey(key)).commit(); 
     } 
     else { 
      putValue(toKey(key), value); 
     } 
    } 

    public boolean containsKey(String key) { 
     return preferences.contains(toKey(key)); 
    } 

    public void removeValue(String key) { 
     preferences.edit().remove(toKey(key)).commit(); 
    } 

    public String getString(String key) throws SecurePreferencesException { 
     if (preferences.contains(toKey(key))) { 
      String securedEncodedValue = preferences.getString(toKey(key), ""); 
      return decrypt(securedEncodedValue); 
     } 
     return null; 
    } 

    public void clear() { 
     preferences.edit().clear().commit(); 
    } 

    private String toKey(String key) { 
     if (encryptKeys) 
      return encrypt(key, keyWriter); 
     else return key; 
    } 

    private void putValue(String key, String value) throws SecurePreferencesException { 
     String secureValueEncoded = encrypt(value, writer); 

     preferences.edit().putString(key, secureValueEncoded).commit(); 
    } 

    protected String encrypt(String value, Cipher writer) throws SecurePreferencesException { 
     byte[] secureValue; 
     try { 
      secureValue = convert(writer, value.getBytes(CHARSET)); 
     } 
     catch (UnsupportedEncodingException e) { 
      throw new SecurePreferencesException(e); 
     } 
     String secureValueEncoded = Base64.encodeToString(secureValue, Base64.NO_WRAP); 
     return secureValueEncoded; 
    } 

    protected String decrypt(String securedEncodedValue) { 
     byte[] securedValue = Base64.decode(securedEncodedValue, Base64.NO_WRAP); 
     byte[] value = convert(reader, securedValue); 
     try { 
      return new String(value, CHARSET); 
     } 
     catch (UnsupportedEncodingException e) { 
      throw new SecurePreferencesException(e); 
     } 
    } 

    private static byte[] convert(Cipher cipher, byte[] bs) throws SecurePreferencesException { 
     try { 
      return cipher.doFinal(bs); 
     } 
     catch (Exception e) { 
      throw new SecurePreferencesException(e); 
     } 
    } 
} 

上面的代码是不我自己，这里是GitHub Page在那里采购。

下面的代码样本用法：

SecurePreferences preferences = new SecurePreferences(context, "user-info", 
                 "YourSecurityKey", true); 
// Put (all puts are automatically committed) 
preferences.put("username", "MyUser"); 
preferences.put("password", "MyPassword"); 
// Get 
String username = preferences.getString("username"); 
String password = preferences.getString("password"); 

免责声明：如果有人来电话的物理访问，他们可能获得的首选项文件和应用程序的二进制文件。这意味着他们可以反编译应用程序并显示加密中使用的密钥，然后解密用户信息。

但是，没有什么是100％安全的。存储任何信息的最安全的方法是根本不存储它。一个坚定的黑客几乎可以破解任何东西，但加密信息会使其变得更加困难。