在现有的SharedPreference值内更改数据类型

Question

I am in the process of cleaning up some bad coding choices in some really old apps. In one of the first apps I did, it has a user login. So, I use SharedPreferences to store the user_id . This should have been a long all along. Unfortunately, I originally stored it as a String .

I am going back and correcting this. However, I of course get a ClassCastException since I am trying to pull out a String as a long .

This is my code on how it works AFTER changing it:

public static void setLoggedInUserId(Context ctx, long id) {
    Editor editor = getSharedPreferences(ctx).edit();
    editor.putLong(PREF_LOGGEDIN_USER_USERID, id);
    editor.apply();
}

public static long getLoggedInUserId(Context ctx) {
    // need to handle String to long conversion here?
    return getSharedPreferences(ctx).getLong(PREF_LOGGEDIN_USER_USERID, 0);
}

What is the cleanest way to handle this so it is as transparent as possible to the user (I don't want to force a log out if possible).

EDIT

As I am typing this, is aa good solution?

return Long.valueOf(getSharedPreferences(ctx).getString(PREF_LOGGEDIN_USER_USERID, 0));

A problem : This would only work the first time to workaround old data; because after that, the preference would be a long based on the setter method.

Next best option: Can I test the type stored in the preference , maybe with a typeof ?

Answer 1

put this in your MainActivity before this value is called for the first time

        if(!prefs.getBoolean("ConversionDone", false)){
            String currentStringValue = prefs.String(PREF_LOGGEDIN_USER_USERID, 0);
            prefs.edit().remove(PREF_LOGGEDIN_USER_USERID).commit();
            prefs.edit().putLong(PREF_LOGGEDIN_USER_USERID, Long.parseLong(currentStringValue)).commit();
            prefs.edit().putBoolean("ConversionDone", true).commit();
        }

and at your next update you can remove it.

Answer 2

1. In getLoggedInUserId , catch the class cast exception

2. Read the (String) value of the shared preference and convert it with Long.parseLong()

3. Create an editor, put the long value, and commit.

This code will run exactly once and then you will no longer have to worry about edge cases.