problems with 'com.android.support:appcompat-v7.27.1.1' in the gradle file

Question

This is my dependencies file and there is an underlined red colored text on the compile 'com.android.support:appcompat-v7.27.1.1'

apply plugin: 'com.android.application'
 android {
compileSdkVersion 27
defaultConfig {
    applicationId "com.abc.mcaproject"
    minSdkVersion 21
    targetSdkVersion 27
    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'])


compile 'com.android.support:appcompat-v7.27.1.1'
implementation 'com.android.support.constraint:constraint-layout:1.1.0'
implementation 'com.google.firebase:firebase-database:11.6.0'
implementation 'com.google.firebase:firebase-messaging:11.6.0'
implementation 'com.google.firebase:firebase-auth:11.6.0'
implementation 'com.google.firebase:firebase-storage:11.6.0'
testImplementation 'junit:junit:4.12'
androidTestImplementation 'com.android.support.test:runner:1.0.2'
androidTestImplementation 'com.android.support.test.espresso:espresso- 
core:3.0.2'
}

apply plugin: 'com.google.gms.google-services'

This because of this I am having problems changing themes in the styles.xml

Answer 1

when you hover over the red line it may show you the image like this which I have attached below.

What it tells you is there is a conflict of the version in some libraries so it suggests us to add those. For my case first, it showed for CardView and then for Design. So I added to it. Below is the code for it.

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:27.1.1'
    implementation 'com.android.support.constraint:constraint-layout:1.1.0'
    implementation 'com.payumoney.sdkui:plug-n-play:1.2.0'
    implementation 'com.android.support:cardview-v7:27.1.1'
    implementation 'com.android.support:design:27.1.1'

    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
}

so kindly add those it may be 2 or more than that. Hope that helps.