但是,在一段时间之后(转到不同的活动等等),onPreferenceChange被调用两次.

我在调试器中看到,对于mListeners的WeakHashMap在开始时为1,然后变为大于1,但不知道为什么？

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    getPrefs();
    int preferencesResource = 0; // R.xml.preferences;
    preferencesResource = getResources().getIdentifier("pref","xml",getPackageName());
    addPreferencesFromResource(preferencesResource);
    listener = new SharedPreferences.OnSharedPreferenceChangeListener() {

        @Override
        public void onSharedPreferenceChanged(SharedPreferences arg0,String arg1) {
            // Why is this called once then sometimes twice!!
            Log.i("PreferencesActivity","OnPreferenceChanged()");
        }
    };
    prefs.registerOnSharedPreferenceChangeListener(listener);
}

protected void onDestroy() {
    super.onDestroy();
    listener = null;
    prefs.unregisterOnSharedPreferenceChangeListener(listener);
    prefs = null;
}

public Preferences getPrefs() {
    if (prefs == null) prefs = new Preferences(this);
    return prefs;
}