regarding problem in barcode detector

[ghost]

Error: Program type already present: android.support.v4.app.BackStackRecord$Op

Code gradle app;

apply plugin: 'com.android.application'

android {
compileSdkVersion 28
defaultConfig {
applicationId "com.example.rudra.barcodereader"
minSdkVersion 15
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'
}
}
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    //noinspection GradleCompatible
    implementation 'com.android.support:appcompat-v7:28.0.0'
    implementation 'com.google.android.gms:play-services:7.8+'
}