regarding problem in barcode detector

[ghost]

trafficstars

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+'
}