空白的最终字段编写器可能尚未初始化答案

【问题标题】：The blank final field writer may not have been initialized空白的最终字段编写器可能尚未初始化
【发布时间】：2014-06-10 21:46:20
【问题描述】：

我正在使用 SharedPreferences 来存储我的应用程序中的一些信息，但正在为活动创建一个对象来管理它。我也在这堂课中使用encrypted-userprefs。我在

中收到错误“空白的最终字段编写器可能尚未初始化”

public StoredPrefsHandler(Context context, boolean secure) throws SecurePreferencesException {

我不知道为什么会发生这种情况，尤其是当它似乎在我的类似课程中工作时。以下是相关代码。请注意，我已经定义了 writer。

public class StoredPrefsHandler {
    public static class SecurePreferencesException extends RuntimeException {
        private static final long serialVersionUID = 3051912281127821578L;

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

    // Stripped down part, more fields unrelevant to the problem have been hidden
    private final String SP_LOCATION = "org.conrogatio.lazyrace.prefs";
    private final String SSP_LOCATION = "org.conrogatio.lazyrace.secureprefs";
    private String LOCATION;
    private Context c;
    private SharedPreferences prefs;
    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 Cipher writer;
    private final Cipher reader;
    private final Cipher keyWriter;

    /**
     * This will initialize an instance of the SecurePreferences class
     * 
     * @param context
     *            your current context.
     * @throws SecurePreferencesException
     */
    public StoredPrefsHandler(Context context, boolean secure) throws SecurePreferencesException {
        c = context;
        secured = secure;
        if (secured) {
            LOCATION = SSP_LOCATION;
            deviceId = Secure.getString(c.getContentResolver(), Secure.ANDROID_ID);
            try {
                this.writer = Cipher.getInstance(TRANSFORMATION);
                this.reader = Cipher.getInstance(TRANSFORMATION);
                this.keyWriter = Cipher.getInstance(KEY_TRANSFORMATION);
                initCiphers(deviceId + SSP_SALT);
                this.prefs = c.getSharedPreferences(SSP_LOCATION, Context.MODE_PRIVATE);
            } catch (GeneralSecurityException e) {
                throw new SecurePreferencesException(e);
            } catch (UnsupportedEncodingException e) {
                throw new SecurePreferencesException(e);
            }
        } else {
            LOCATION = SP_LOCATION;
        }
        update();
    }

【问题讨论】：

如果您将 secure=false 传递给此构造函数，则最终字段 writer、reader 和 keyWriter 保持未初始化。因此编译器抱怨。如果您知道不需要它们，请将它们设置为 null。
如果也使它们成为非最终版本，这似乎也有效

标签： android sharedpreferences encryption

【解决方案1】：

尝试像这样初始化决赛：

 private final Cipher writer=null;
 private final Cipher reader=null;
 private final Cipher keyWriter=null;

【讨论】：

因为如果secure==true我也得在以后重新初始化它们，所以最后一个参数需要去掉
你可以让它们成为非最终的

【解决方案2】：

如果 secure==false，writer、reader 和 keyWriter 将未初始化。这可以通过提前初始化它们来解决，但也可以将它们设置为非最终的。

private final Cipher writer;
private final Cipher reader;
private final Cipher keyWriter;

变成

private Cipher writer = null;
private Cipher reader = null;
private Cipher keyWriter = null;

【讨论】：