changeVersion doesn't support multithreading. -> NullPointerException

[toy-lin]

Very thanks for your product,but i have got a NullPointerException while migrating data,can anybody give me some advice?

java.lang.NullPointerException:
Attempt to invoke virtual method 'java.lang.String java.lang.Object.toString()' on a null object reference
at net.grandcentrix.tray.core.SharedPreferencesImport.onPostMigrate(SharedPreferencesImport.java:79)
at net.grandcentrix.tray.core.SharedPreferencesImport.onPostMigrate(SharedPreferencesImport.java:38)
at net.grandcentrix.tray.core.Preferences.migrate(Preferences.java:125)
at ...module.sp.CookiePreferences.importSP(CookiePreferences.java:47)
at ...module.sp.CookiePreferences.onCreate(CookiePreferences.java:29)
at net.grandcentrix.tray.core.Preferences.changeVersion(Preferences.java:262)
at net.grandcentrix.tray.core.Preferences.isVersionChangeChecked(Preferences.java:292)
at net.grandcentrix.tray.core.Preferences.(Preferences.java:58)
at net.grandcentrix.tray.core.AbstractTrayPreference.(AbstractTrayPreference.java:31)
at net.grandcentrix.tray.TrayPreferences.(TrayPreferences.java:43)
at net.grandcentrix.tray.TrayPreferences.(TrayPreferences.java:48)
at ..*.module.sp.CookiePreferences.(CookiePreferences.java:23)

And below is code in CookiePreferences:

`public class CookiePreferences extends TrayPreferences {
private static final String TAG = CookiePreferences.class.getSimpleName();
public static final String MODULE = "cookie";
private static final String SP_NAME = "mycookie";
public CookiePreferences(Context context) {
super(context, MODULE, 1);
}

@Override
protected void onCreate(int initialVersion) {
    super.onCreate(initialVersion);
    importSP();
}

private void importSP() {
    final SharedPreferences sps = getContext().getSharedPreferences(SP_NAME, Context.MODE_PRIVATE);
    HashMap<String, Object> all = new HashMap<>(sps.getAll());

    Set<Map.Entry<String, Object>> set = all.entrySet();
    for (Map.Entry<String, Object> en : set) {
        String key = en.getKey();
        SharedPreferencesImport ip = new SharedPreferencesImport(getContext(), SP_NAME, key, key);
        migrate(ip);
    }
}

}`

Version:

compile 'net.grandcentrix.tray:tray:0.11.1'

[toy-lin]

Oh, i have found the problem.I thought Tray is thread safe but it's not.
In my case ,method 'onCreate' was invoked twice from different thread.
Am i wrong with my code?

[toy-lin]

Yes，Tray isn't thread safe.The lock to check version change is a TrayPreferences object, so if we create more than one TrayPreferences object in different thread , method 'onCreate' would probably be invoked more than 1 time.
"synchronized void changeVersion(final int newVersion)"

[passsy]

Good finding. We will fix that

[bdelville]

The same problem would happen in onCreate if multiple process start at the same time