Android Studio 3.0 cannot resolve symbol Theme

Question

As stated in style.xml, there is a weird error, which shows Cannot resolve symbol \'Theme\', which is quite strange.

See pic of the error :-

My Project Spe

Answer 1

Had the same issue after upgrading to Android Studio 3.1 (EDIT: bug still present at v3.1.3). What worked for me was clicking File > Close Project and then reopening the project from Studio's dialog.

Answer 2

Goto File -> Invalidate Caches / Restart... -> Invalidate and Restart

Android Studio will sort-of close and delete all caches, indexes, etc.. Then, Android Studio will open again. Indexing will be done and you're ready to proceed.

Answer 3

What worked for me was to click on Gradle to open the Gradle projects tool window and than on refresh. I think some depedencies where not loaded correctly.

Answer 4

Solution 1:

1. GOTO > 'build.gradle(Module:app)',
2. ADD > "buildToolsVersion '28.0.2'" as following :

android {
    signingConfigs {}
    compileSdkVersion 28
    defaultConfig
    {
        applicationId "com.example.project"
        minSdkVersion 21
        targetSdkVersion 28
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes
    {
        release
        {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }

    buildToolsVersion '28.0.1'
}

3. Click on 'Sync Now', and it's done.
4. GOTO > 'File' > 'Invalidate Cache/Restart'.
5. Done.

If That doesn't work, following might help (Solution 2) :

1. GOTO > 'SDK Manager' > 'SDK Tools' > Click on 'Show Package Details',
2. Check if there is a NEW Version of 'SDK Build-Tools' Available,
3. Then Download it and Change to newer version "buildToolsVersion '28.0.x'" in 'build.gradle (Module:app)',
4. Sync again.
5. GOTO > 'File' > 'Invalidate Cache/Restart'.
6. Done.

If That doesn't work, following might help (Solution 3) :

1. Remove/Cut following dependencies :

   implementation 'com.android.support:appcompat-v7:x.x.x'
   implementation 'com.android.support:design:x.x.x'
   

2. Click on 'Sync Now',

3. Add/Paste dependencies again and Sync again.
4. Done.

NOTE : You can do Solution 1 then 2 then 3 for better results.

Hope it helped :)