Variable 'snackbar' might not have been initialized

Question

I am getting this error message saying that Variable "snackbar" might not have been initialized.

The following is part of my MainActivity.java code:

public class NetworkChangeReceiver extends BroadcastReceiver {

@Override
public void onReceive(Context context, Intent intent) {

    NetworkInfo info = intent.getParcelableExtra(WifiManager.EXTRA_NETWORK_INFO);

    if (info != null && info.isConnected()) {
        final Snackbar snackbar = Snackbar.make(findViewById(android.R.id.content), "WiFi change detected; updating information...", Snackbar.LENGTH_LONG)
            .setAction("DISMISS", new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    snackbar.dismiss();
                }
            });
            snackbar.setActionTextColor(Color.BLUE);
            snackbar.show();

            getWifi();
    }
}
}

I had read the accepted Stack Overflow answer here and it suggests that I initialize snackbar immediately after public class NetworkChangeReceiver extends BroadcastReceiver. So, I changed the code to:

/* no changes here */
@Override
public void onReceive(Context context, Intent intent) {
    Snackbar snackbar = null;

    /* no changes here */
    if (...) {
        snackbar = Snackbar.make(...);
    }

    /* no changes here */
}

But this gives me an error Variable "snackbar" is accessed from within inner class, needs to be declared final and a warning Method invocation "snackbar.dismiss()" may produce "java.lang.NullPointerException".

Any suggestions on how to solve this? Thanks!

Andy Turner · Accepted Answer · 2016-02-04T12:28:04.243

9

Split up your chained method calls:

final Snackbar snackbar = Snackbar.make(findViewById(android.R.id.content), "WiFi change detected; updating information...", Snackbar.LENGTH_LONG);
snackbar.setAction("DISMISS", new View.OnClickListener() {
    @Override
    public void onClick(View v) {
      snackbar.dismiss();
    }
  });

This way, snackbar is definitely assigned before you create the OnClickListener.

edited Feb 04 '16 at 12:28

answered Feb 04 '16 at 12:18

Andy Turner

137,514
11
162
243

Just curious, is this a bug in Android studio or am I meant to code it the way you've suggested? – Feb 04 '16 at 15:04
This is not a bug. It is because of the way that anonymous classes are implemented, which is actually quite clear once you poke around a bit. I was actually writing up a detailed explanation... will continue and post a link here. – Andy Turner Feb 04 '16 at 15:06
Thanks @Andy Turner, looking forward to reading your article :) – Feb 04 '16 at 15:07
1

@YikJin http://stackoverflow.com/questions/35204884/variable-example-might-not-have-been-initialized-in-anonymous-class/35204885#35204885 – Andy Turner Feb 04 '16 at 15:24
1

Thanks @Andy Turner! That was helpful! Hope people who had this question find your answer useful too. – Feb 04 '16 at 15:40

score -5 · Answer 2 · answered Feb 04 '16 at 12:21

-5

As a workaround to

Variable "snackbar" is accessed from within inner class, needs to be declared final

you can make that variable a final one-element array

answered Feb 04 '16 at 12:21

Meegoo

417
5
13

Yes it is, but if you REALLY know what you are doing, it can work. But, yeah, you shouldn't do that. – Meegoo Feb 04 '16 at 12:32
2

Even if you REALLY know what you're doing, it is still terrible code. – Niels Masdorp Feb 04 '16 at 12:34
1

If you think this is a good solution then you certainly DON'T know what you are doing... – Adriaan Koster Feb 05 '16 at 10:53

Variable 'snackbar' might not have been initialized

2 Answers2

Linked