Android: Manifest merger failed : uses-sdk:minSdkVersion 19 cannot be smaller than version 21 declared in library

Question

I have an Android (Java) source code, in which I have integrated the Flutter module. When I run my Android application in Android Studio I get the following error. I know the solution is very straightforward. Perhaps the error itself suggests the solutions. However, I can't implement those solutions as I get the following error for multiple flutter packages I am using, in my Flutter source code. How do I resolve this without changing minSdkVersion in the Android app?

Let me explain the structure of the source code I have.

--Android_A  --- It has all the Android source code
--Flutter_B  --- It has flutter code
    --Flutter_C  --- It is a git submodule with flutter source code again.

The pubspec.yaml inside each flutter module above has a line indicating the dependencies. E.g

Flutter_C/pubspec.yaml has the following line

Flutter_B:
     path: ../../Flutter_B

Similarly Flutter_B/pubspec.yaml has the following line

Flutter_C:
     path: Flutter_C

Finally, Android_A/settings.gradle has the following lines.

include ':app'
setBinding(new Binding([gradle: this]))
evaluate(new File(
        settingsDir.parentFile,
        'Flutter_B/.android/include_flutter.groovy'
))

Manifest merger failed : uses-sdk:minSdkVersion 19 cannot be smaller than version 21 declared in library [:payu_checkoutpro_flutter] 
~/pm_module/.android/plugins_build_output/payu_checkoutpro_flutter/intermediates/merged_manifest/debug/AndroidManifest.xml as the library might be using APIs not available in 19
    Suggestion: use a compatible library with a minSdk of at most 19,
        or increase this project's minSdk version to at least 21,
        or use tools:overrideLibrary="com.payubiz.payu_checkoutpro_flutter" to force usage (may lead to runtime failures)

I tried changing minSdkVersion as the error suggests, but unfortunately, I receive this error for so many packages.
There are other SO posts similar to this problem, but they are also talking about a single package.

It was working well in the current setup, it suddenly started throwing this issue. I even ran the git reset and flutter clean, flutter pub get and similar commands.

Answer 1

If you haven't already, you can enable multidex support in your Android project. Multidex support allows your app to build and run on older Android versions that have a limitation on the number of methods in a single dex file. To enable multidex, follow these steps : In your build.gradle file (typically located in the android/app directory), add the following lines inside the android block:

android {
    defaultConfig {
        ...
        multiDexEnabled true
    }
}

Also, make sure to include the multidex dependency in your dependencies block:

dependencies {
    implementation 'com.android.support:multidex:1.0.3'
}

Finally, update your AndroidManifest.xml to include the multidex application class :

<application
    android:name="androidx.multidex.MultiDexApplication">
    ...
</application>