我有一个用户名，密码和复选框（在文本旁边'记住我'）。
如何实现记住我的功能以保存用户名和密码数据？
任何帮助都将不胜感激。
答案 0 :(得分：40)
你可以save values associated with your application using Preferences。
定义一些静态以存储首选项文件名和您将要使用的键：
public static final String PREFS_NAME = "MyPrefsFile";
private static final String PREF_USERNAME = "username";
private static final String PREF_PASSWORD = "password";
然后您将保存用户名和密码，如下所示：
getSharedPreferences(PREFS_NAME,MODE_PRIVATE)
.edit()
.putString(PREF_USERNAME, username)
.putString(PREF_PASSWORD, password)
.commit();
所以你会像这样检索它们：
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，如果您不想命名首选项文件，则可以使用默认值：
SharedPreferences pref = PreferenceManager.getDefaultSharedPreferences(this);
答案 1 :(得分：14)
应该注意的是，虽然接受的答案成功存储和检索凭证，但它将它们存储为纯文本。
这意味着密码将在root电话上显示。如果您选择使用SharedPreferences在应用程序中存储密码等敏感信息，那么 Reto Meier （Android开发关系技术主管）指出：您应该在非常至少encrypt the password才能将其写入磁盘。
这是一个在将用户信息存储到SharedPreferences之前加密用户信息的实现：
/*
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);
}
}
}
上面的代码不我自己的代码，这里是GitHub Page来源代码。
以下是代码的示例用法：
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：如果某人对手机具有物理访问权限，则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。
然而，没有什么是100％安全的。存储任何信息的最安全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，但加密信息将使其变得更加困难。