如何实现'；记住我'；Android活动中的功能？

我有用户名、密码和复选框（在文本“记住我”旁边）

如何实现“记住我”功能来保存用户名和密码数据

任何帮助都将不胜感激。

您可以

定义一些static来存储首选项文件名和要使用的键：

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

然后按如下方式保存用户名和密码：

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

因此，您可以这样检索它们：

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，如果不想命名首选项文件，可以使用默认值：

SharedPreferences pref = PreferenceManager.getDefaultSharedPreferences(this);

---

应该注意的是，尽管接受的答案成功地存储和检索了凭据，但它将它们存储为纯文本

这意味着密码在根手机上很容易看到。如果您选择使用

SharedReferences

在应用程序中存储敏感信息，如密码，则正如Reto Meier（Android开发关系技术负责人）所述：至少在将其写入磁盘之前，您应该这样做

下面是一个在将用户信息存储在

SharedReferences

中之前对其进行加密的实现：

/*
Copyright (C) 2012 Sveinung Kval Bakken, sveinung.bakken@gmail.com

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);
        }
    }
}

上面的代码不是我自己的，这里是它的来源

下面是代码的示例用法：

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：如果有人可以物理访问手机，他们可能会访问首选项文件和应用程序的二进制文件。这意味着他们可以对应用程序进行反编译，并显示加密中使用的密钥，然后取消对用户信息的加密

---

然而，没有什么是100%安全的。存储任何信息最安全的方法是根本不存储它。一个有决心的黑客几乎可以攻击任何东西，但加密信息会使其更加困难

是的，您可以从任何活动中访问首选项。如果我一次又一次创建同名文件，它将覆盖使用相同名称的前一个文件，或者什么？？第二个问题：我可以删除我创建的这个文件吗？？？？或者将其设置为空？？？@Benny任何具有root访问权限的人都可以访问首选项文件并可以看到清除密码。我认为保存密码的散列会更安全。@Tim:hash是一条单行道，没有简单的方法检索密码。加密密码将是一条出路。但是，如果有人获得了对二进制文件的访问权，并且拥有对设备的root访问权，那么他们可以获得密钥并取消对存储的密码的加密。所以你并没有获得太多的安全性——但这总比什么都不做并以纯文本形式存储要好。在SharedReference上保存用户名和密码是个糟糕的主意。使用SharedPreferences存储非敏感数据。请检查此项。在一段时间后如何重置首选项。因此，30天前登录的用户必须再次登录