Android gives error "Cannot fit requested classes in a single dex file"

Add dependency in build.gradle file:

implementation 'androidx.multidex:multidex:2.0.1'

In build.gradle's defaultConfig section add:

multiDexEnabled true

More details here: Error:Cannot fit requested classes in a single dex file.Try supplying a main-dex list. # methods: 72477 > 65536

Running RN 0.62 and this worked for me with successful build.

Update build.gradle

classpath('com.android.support:multidex:1.0.3')

Update defaultConfig

multiDexEnabled true

After those 2 changes, restart the gradle build again.

Multidex is not always the solution to the problem, is true that it will generate more dex files to fit your method count, but be sure to not import more methods that you need because this in long term will make your builds slower than before.

For example, if you just need to use the location library from play services, you have two options

First one is implementing the whole play-services libraries that will come with location

implementation 'com.google.android.gms:play-services:11.8.0'

These whole libraries could have more than 40.000+ methods (is only an estimative, I don't really know the total count), being close to reaching the 65536 limit methods.

Instead you should be targeting only the libraries you will use instead of the whole bundle of libraries

in this case

implementation 'com.google.android.gms:play-services-location:11.8.0'

could have just 50 - 100 methods to work with, which will be better at build time than loading a whole bunch of methods from the whole library package that you won't ever use.

this is just a tip to avoid getting

Cannot fit requested classes in a single dex file.

For minSdkVersion above android 5.0 API 20 +

Android 5.0 and higher uses a runtime called ART which nativelysupports loading multiple dex files from application APK files. ARTperforms pre-compilation at application install time which scans forclasses(..N).dex files and compiles them into a single .oat file forexecution by the Android device. For more information on the Android5.0 runtime, see Introducing ART.

If you are targeting lower devices (Android 4.1 API 16) or before Android 5 (API 20)

Versions of the platform prior to Android 5.0 use the Dalvik runtimefor executing app code. By default, Dalvik limits apps to a singleclasses.dex bytecode file per APK. In order to get around thislimitation, you can use the multidex support library, which becomespart of the primary DEX file of your app and then manages access tothe additional DEX files and the code they contain.

You will need to use multidex in this last case