Why does Android Studio 3.1.1 always display Unresolved reference when I reopen a project for the first time?

Question

I have import info.dodata.mirror.R, I always get the warning information Unresolved reference: R when I reopen a project for the first time, just like the following image.

I have to click the menu Build -> Rebuild project to rebuild the project, or I close the project and reopen it again in Android Studio 3.1.1 to resolve the problem.

Both my office PC and home PC with windows 7 x64 meet the same problem. How can I fix it? Thanks!

Image

To ice1000:

Thanks! Do you mean that I should click Refresh All Gradle Projects button?

BTW, both my two PC are 8G memory, i7-4600 CPU 2.4GHZ, windows 7 x64, are my PCs too old? — HelloCW, Apr 15 '18 at 01:34

ice1000 · Accepted Answer · 2018-04-15T08:50:51.670

2

Because R.java is generated from your resource xml files, and it's not always there. It takes few seconds to get generated.

I don't know how Android Studio resolves that file, but it's also possibly just a dummy file which is not there when you're not compiling your code. So it's quite normal to see unresolved reference in the very beginning when AS load your project.

To quickly get your project refreshed you may need refresh your project instead of rebuild it:

If you can't find that button, try pressing Ctrl+Shift+A, you'll see a popup, and you can search refresh:

edited Apr 15 '18 at 08:50

answered Apr 15 '18 at 01:36

ice1000

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In fact, few seconds passed, Android Studio still display Unresolved reference, you know that Rebuild Project will take a long time – HelloCW Apr 15 '18 at 01:53
It's a bad point of Android Studio's internal implementation. You don't need to rebuild, you just need "refresh" which doesn't actually compile your code but reloads all the settings. – ice1000 Apr 15 '18 at 04:01
Thanks! How to "refresh" ? – HelloCW Apr 15 '18 at 06:30
I can't find "refresh" button on Android Studio – HelloCW Apr 15 '18 at 06:48
Thanks! would you please see my modified question? – HelloCW Apr 15 '18 at 14:23
Yes, I mean exactly that. – ice1000 Apr 15 '18 at 23:07

Why does Android Studio 3.1.1 always display Unresolved reference when I reopen a project for the first time?

1 Answers1