Google material design library error Program type already present: android.support.v4.app.INotificationSideChannel$Stub$Proxy

I've been struggling all day with this issue too. Finally I managed to compile and run the project successfully.

First of all, get rid of this:

implementation 'com.android.support:appcompat-v7:28.0.0-alpha1'
implementation 'com.android.support:design:28.0.0-alpha1'
implementation 'com.android.support:support-v4:28.0.0-alpha1'

Add the following in your gradle.properties file:

android.useAndroidX = true
android.enableJetifier = false

And finally, sync the project and then compile.

If it doesn't work, clean the project and then rebuild.

PS: I can't get targetSdkVersion 'p' to work. My build.gradle file end up as follows:

apply plugin: 'com.android.application'

android {
    compileSdkVersion 'android-P'
    defaultConfig {
        applicationId "com.github.alvarosct02.demo"
        minSdkVersion 19
        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'])

    implementation 'com.google.android.material:material:1.0.0-alpha1'
    implementation 'com.android.support.constraint:constraint-layout:1.1.0'

    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'

}

Hope it works for you too.

I wasted 2 days looking for a solution. Anyone who's still looking for a solution can follow the steps below:

1. Update your Android Studio to the latest version.

2. Update your compileSdkVersion and targetSdkVersion to 28.

   android {
   
       compileSdkVersion 28
   
       defaultConfig {
           applicationId "com.your.appid"
           minSdkVersion 19
           targetSdkVersion 28
           versionCode 50
           versionName "1.50"
           testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
           multiDexEnabled true
           setProperty("archivesBaseName", "your-app-$versionName")
           resConfigs "en"
        }
   }
   

3. Go to your project structure and change your gradle version to 4.10.

4. Add this dependency first:

   implementation 'com.google.android.material:material:1.0.0'
   

5. Now remove all the support library dependencies:

   implementation "com.android.support:design:$SUPPORT_LIBRARY_VERSION"
   implementation "com.android.support:support-v4:$SUPPORT_LIBRARY_VERSION"
   implementation "com.android.support:appcompat-v7:$SUPPORT_LIBRARY_VERSION"
   implementation "com.android.support:recyclerview-v7:$SUPPORT_LIBRARY_VERSION"
   implementation "com.android.support:cardview-v7:$SUPPORT_LIBRARY_VERSION"
   implementation 'com.android.support.constraint:constraint-layout:1.1.3'
   implementation 'com.android.support:multidex:1.0.3'
   testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
   androidTestImplementation('com.android.support.test.espresso:espresso- 
      core:2.2.2', {
   exclude group: 'com.android.support', module: 'support-annotations'
   exclude group: 'com.google.code.findbugs', module: 'jsr305'
   })
   

6. Now paste the following into your gradle.properties file:

   android.useAndroidX = true
   android.enableJetifier = true
   

7. In your project level build.gradle file:

   dependencies {
       classpath 'com.android.tools.build:gradle:3.2.0'
       classpath 'com.google.gms:google-services:4.1.0'
   };
   

For those who are using Butterknife add below lines in your project level build.gradle file:

allprojects {
    repositories {
    google()
    jcenter()
    maven { url "https://jitpack.io" }
    maven { url "https://dl.bintray.com/drummer-aidan/maven/" }
    maven { url "https://oss.sonatype.org/content/repositories/snapshots" }
  }
}

And in your module build.gradle file add below dependencies:

 implementation "com.jakewharton:butterknife:9.0.0-SNAPSHOT"
 annotationProcessor "com.jakewharton:butterknife-compiler:9.0.0-SNAPSHOT"

8. Now Goto Build > Rebuild Project then you might be getting a lot of errors.

9. Now refer this link.
   
   It has the list of all the old (android.support) vs new (androidx.*) dependencies.
   
   Replace all your old imports with the new ones
   (Use replaceAll feature of android studio [ctrl + shift + R] which will save you some time).

1. Finally After refactoring all the old libraries with the new ones:
   Rebuild the project again and hopefully it should work.

Note: You can also use Refactor > Migrate to androidx in android studio but it didn't work for me.

I started getting this error after upgrading the ButterKnife to the version 8.8.1.

So, I run the command gradle -q dependencies to generate a dependency report, after that you should see where D8 is coming from. In my case from the "ButterKnife" library:

+--- com.jakewharton:butterknife:8.8.1
|    |    \--- com.android.support:support-compat:d8

Also you can see your android dependencies by going to your Android Studio Gradle view (In Android Studio tool bar navigate to "View/Tool Windows/Gradle"), and selecting the target "androidDependencies" under "My-Project-Name/Tasks/android" (Double click to run or Right click and run).

To solve this problem I added this piece of code exclude module: 'support-compat' to my "app/build.gradle" as below:

implementation ('com.jakewharton:butterknife:8.8.1') { 
     exclude module: 'support-compat' 
} 
annotationProcessor 'com.jakewharton:butterknife-compiler:8.8.1'

Hope it works for someone else :] Cheers!