sharedPreferencesInstance.getAll().size()

要检索先前存储的所有密钥,可以使用keySet(),如以下代码段所示：

SharedPreferences prefs = this.getSharedPreferences("myshared",Context.MODE_PRIVATE);
Map<String,?> entries = prefs.getAll();
Set<String> keys = entries.keySet();
for (String key : keys) {

}