android应用程序中的对象反序列化问题

Question

我有一个类名ObjectSerializer。这就是：

public class ObjectSerializer {
public static String serialize(Serializable obj) throws IOException {
    if (obj == null)
        return "";
    ByteArrayOutputStream serialObj = new ByteArrayOutputStream();
    ObjectOutputStream objStream = new ObjectOutputStream(serialObj);
    objStream.writeObject(obj);
    objStream.close();
    return encodeBytes(serialObj.toByteArray());
}

public static Object deserialize(String str) throws IOException,
        ClassNotFoundException {
    if (str == null || str.length() == 0)
        return null;
    ByteArrayInputStream serialObj = new ByteArrayInputStream(
            decodeBytes(str));
    ObjectInputStream objStream = new ObjectInputStream(serialObj);
    return objStream.readObject();
}

public static String encodeBytes(byte[] bytes) {
    StringBuffer strBuf = new StringBuffer();

    for (int i = 0; i < bytes.length; i++) {
        strBuf.append((char) (((bytes[i] >> 4) & 0xF) + ((int) 'a')));
        strBuf.append((char) (((bytes[i]) & 0xF) + ((int) 'a')));
    }

    return strBuf.toString();
}

public static byte[] decodeBytes(String str) {
    byte[] bytes = new byte[str.length() / 2];
    for (int i = 0; i < str.length(); i += 2) {
        char c = str.charAt(i);
        bytes[i / 2] = (byte) ((c - 'a') << 4);
        c = str.charAt(i + 1);
        bytes[i / 2] += (c - 'a');
    }
    return bytes;
}
}

现在我已经使用控制台应用程序进行了测试，如下所示：

    public static void main(String[] args) throws IOException,
        ClassNotFoundException {
    HighScore highScore = new HighScore();
    highScore.setScore(10);
    highScore.setUsername("rokon");

    ArrayList<HighScore> list = new ArrayList<HighScore>();
    list.add(highScore);
    String seralized = null;
    try {
        seralized = ObjectSerializer.serialize(list);

        System.out.println(seralized);
    } catch (IOException e) {
        e.printStackTrace();
    }

    Object obj = ObjectSerializer.deserialize(seralized);
    ArrayList<HighScore> l = (ArrayList<HighScore>) obj;

    HighScore h= l.get(0);
    System.out.println(h.getUsername() + "\t" + h.getScore());
}

但同样的事情在我的android应用程序中不起作用。谁能告诉我android应用程序的问题是什么？

和我在android类中使用的代码

    public class HighScorePreferenceUtil {
public static String APP_SHARED_PREF = "com.wneeds.quiz";
private SharedPreferences preferences;
private final String key = "HighScore";
private Editor editor;
private ArrayList<HighScore> highScores;
private Context context;

public HighScorePreferenceUtil(Context context) {
    this.preferences = context.getSharedPreferences(APP_SHARED_PREF,
            Activity.MODE_PRIVATE);
    this.context = context;
}

public void addScore(HighScore score) {
    if (score != null) {
        try {
            this.editor = preferences.edit();
            editor.putString(key, ObjectSerializer.serialize(score));
            editor.commit();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    editor.commit();
}

public ArrayList<HighScore> getScores() {
    if (highScores == null) {
        highScores = new ArrayList<HighScore>();
    }
    try {
        String scores = preferences.getString(key, "empty");
        Object obj = ObjectSerializer.deserialize(scores);

        if (!scores.equals("empty")) {
            ArrayList<HighScore> list = (ArrayList<HighScore>) obj;
            highScores = list;
        }

    } catch (IOException e) {
        e.printStackTrace();
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    }

    return highScores;
}
}

我要去找ClassCastException。Herte是logCat的报道。

09-13 22:29:27.083: ERROR/AndroidRuntime(983): FATAL EXCEPTION: main
09-13 22:29:27.083: ERROR/AndroidRuntime(983): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.rokon/com.rokon.SharedPreferenceDemoActivity}: java.lang.ClassCastException: com.rokon.HighScore
09-13 22:29:27.083: ERROR/AndroidRuntime(983):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
09-13 22:29:27.083: ERROR/AndroidRuntime(983):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
09-13 22:29:27.083: ERROR/AndroidRuntime(983):     at android.app.ActivityThread.access$2300(ActivityThread.java:125)
09-13 22:29:27.083: ERROR/AndroidRuntime(983):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
09-13 22:29:27.083: ERROR/AndroidRuntime(983):     at android.os.Handler.dispatchMessage(Handler.java:99)
09-13 22:29:27.083: ERROR/AndroidRuntime(983):     at android.os.Looper.loop(Looper.java:123)
09-13 22:29:27.083: ERROR/AndroidRuntime(983):     at android.app.ActivityThread.main(ActivityThread.java:4627)
09-13 22:29:27.083: ERROR/AndroidRuntime(983):     at java.lang.reflect.Method.invokeNative(Native Method)
09-13 22:29:27.083: ERROR/AndroidRuntime(983):     at java.lang.reflect.Method.invoke(Method.java:521)
09-13 22:29:27.083: ERROR/AndroidRuntime(983):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
09-13 22:29:27.083: ERROR/AndroidRuntime(983):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
09-13 22:29:27.083: ERROR/AndroidRuntime(983):     at dalvik.system.NativeStart.main(Native Method)
09-13 22:29:27.083: ERROR/AndroidRuntime(983): Caused by: java.lang.ClassCastException: com.rokon.HighScore
09-13 22:29:27.083: ERROR/AndroidRuntime(983):     at com.rokon.HighScorePreferenceUtil.getScores(HighScorePreferenceUtil.java:51)
09-13 22:29:27.083: ERROR/AndroidRuntime(983):     at com.rokon.SharedPreferenceDemoActivity.onCreate(SharedPreferenceDemoActivity.java:54)
09-13 22:29:27.083: ERROR/AndroidRuntime(983):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
09-13 22:29:27.083: ERROR/AndroidRuntime(983):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627
09-13 22:29:27.083: ERROR/AndroidRuntime(983):     ... 11 more

Answer 1

我不知道这是否原因，但：

您应该检查调试器，确认您有一个传递给serialize方法的HighScore的工作实例。如果传递null，则返回一个空字符串，然后将其添加到addScore()方法中的SharedPreferences中。如果发生这种情况，当您反序列化它时，您将得到空字符串。空字符串将创建ClassCastException。

所以我的建议是:进行更多的null检查和/或在尝试序列化null引用时停止返回空字符串，而返回“空”字符串，以便!scores.equals("empty")在这种情况下也能工作。