SharedPreferences.OnSharedPreferenceChangeListener什么时候调用

SharedPreferences prefs = 
    PreferenceManager.getDefaultSharedPreferences(this);

prefs.registerOnSharedPreferenceChangeListener(
    new SharedPreferences.OnSharedPreferenceChangeListener() {
        public void onSharedPreferenceChanged(
            SharedPreferences prefs, String key) {

            System.out.println(key);
        }
    });

The trouble is, the listener is not always called. It works for the first few times a preference is changed, and then it is no longer called until I uninstall and reinstall the app. No amount of restarting the application seems to fix it.

在第一次被改变的时候就开始掉用