Bug 'Plugin with id 'com.android.library' not found.' when include java module in flutter project

Question

I'm creating a Flutter Project and I need import a Java module to use the Samsung IAP, but, when I insert the module, I get this problem: Plugin with id 'com.android.library' not found.

This is the build.gradle of the Samsung IAP Helper (IAP6Helper):

apply plugin: 'com.android.library'
android {
    compileSdkVersion 26
    buildToolsVersion '28.0.3'

    defaultConfig {
        minSdkVersion 18
        targetSdkVersion 26
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.txt'
        }
    }
}

dependencies {
}

This is the build.gradle of the Samsung IAP Sample (IAP6Sample):

apply plugin: 'com.android.application'

android {
    compileSdkVersion 26
    buildToolsVersion '28.0.3'

    defaultConfig {
        applicationId 'com.samsung.android.sdk.iap.v6.sample1'
        minSdkVersion 18
        targetSdkVersion 26
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.txt'
        }
    }

    productFlavors {
    }
}

dependencies {
    implementation project(':IAP6Helper')
}

I see in some

dependencies {
    classpath 'com.android.tools.build:gradle:7.1.3'
}

I already saw in some answers here that I should add the code below in my code, but it always was and nothing solves it.

Sorry my bad English.