android - SharedPreferences always get default value in my existing app but when created new app its ok

Question

SharedPreferences doesn't work correct in one existing apps. I tried many different ways but still not working. Always get default values app start again.

• It's working when I use same code in created new app.
• It's working all of other existing apps.

Do you know why?

    String default_user = "Default_User";
    SharedPreferences pref = this.getSharedPreferences("TEST_SHAREDPREF", MODE_PRIVATE);
    String user = pref.getString("user", default_user);
    Log.d("SHARED CHECK", user);
    if (user.equals(default_user)) {
        SharedPreferences.Editor edit = pref.edit();
        edit.putString("user", "new_user");
        boolean ok = edit.commit();
        user = pref.getString("user", default_user);
        Log.d("SHARED WRITE", user);
        Toast.makeText(this, user + " Save process: " + ok, Toast.LENGTH_LONG).show();
    } else {
        Log.d("SHARED READ", user);
        Toast.makeText(this, "READ SharedPrefs: " + user, Toast.LENGTH_LONG).show();
    }

EDIT: log results

that block always return this for which is incorrect app and I don't know why

    //first run
    SHARED CHECK Default_User
    SHARED WRITE new_user

    //each time after first
    SHARED CHECK Default_User
    SHARED WRITE new_user

That block always return this for which are all apps

    //first run
    SHARED CHECK Default_User
    SHARED WRITE new_user

    //each time after first
    SHARED CHECK new_user
    SHARED READ new_user

Answer 1

When you call apply() or commit() the changes are first saved to the app's memory cache and then Android attempts to write those changes onto the disk. What is happening here is that your commit() call is failing on the disk but the changes are still made to the app's memory cache, as is visible in the source.

It is not enough to read the value from the SharedPreferences as that value might not reflect the true value that is on the disk but only that stored in the memory cache.

What you are failing to do is to check the boolean value returned from the commit() call, it is probably false for your problematic case. You could retry the commit() call a couple of times if false is returned.