Android ClassNotFoundException with appcompat-v7:28.0.0

Question

I'm developing an Android application and I try to use the toolbar to add some functionality on it; that's why I'm using appcompat-v7 module. I have followed this tutorial (Sorry because it's in spanish) and I have updated my IDE with the Compatibility Support package, I also added the new module to my Gradle file and I have updated the design XML of my app with this new toolbar (I can see this toolbar in the design editor).

But, when I launch my application, I get following error:

     java.lang.RuntimeException: Unable to start activity ComponentInfo{xxx}: android.view.InflateException: Binary XML file line #10: Binary XML file line #10: Error inflating class android.support.v7.widget.Toolbar
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2913)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:193)
        at android.app.ActivityThread.main(ActivityThread.java:6669)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
     Caused by: android.view.InflateException: Binary XML file line #10: Binary XML file line #10: Error inflating class android.support.v7.widget.Toolbar
     Caused by: android.view.InflateException: Binary XML file line #10: Error inflating class android.support.v7.widget.Toolbar
     Caused by: java.lang.ClassNotFoundException: Didn't find class "android.support.v7.widget.Toolbar" on path: DexPathList[[zip file "/data/app/com.gomar.gomar_sanidad-xZFFzOUSrlLb9osLbk1xcA==/base.apk", zip file "/data/app/com.gomar.gomar_sanidad-xZFFzOUSrlLb9osLbk1xcA==/split_lib_dependencies_apk.apk", zip file "/data/app/com.gomar.gomar_sanidad-xZFFzOUSrlLb9osLbk1xcA==/split_lib_resources_apk.apk", zip file "/data/app/com.gomar.gomar_sanidad-xZFFzOUSrlLb9osLbk1xcA==/split_lib_slice_0_apk.apk", zip file "/data/app/com.gomar.gomar_sanidad-xZFFzOUSrlLb9osLbk1xcA==/split_lib_slice_1_apk.apk", zip file "/data/app/com.gomar.gomar_sanidad-xZFFzOUSrlLb9osLbk1xcA==/split_lib_slice_2_apk.apk", zip file "/data/app/com.gomar.gomar_sanidad-xZFFzOUSrlLb9osLbk1xcA==/split_lib_slice_3_apk.apk", zip file "/data/app/com.gomar.gomar_sanidad-xZFFzOUSrlLb9osLbk1xcA==/split_lib_slice_4_apk.apk", zip file "/data/app/com.gomar.gomar_sanidad-xZFFzOUSrlLb9osLbk1xcA==/split_lib_slice_5_apk.apk", zip file "/data/app/com.gomar.gomar_sanidad-xZFFzOUSrlLb9osLbk1xcA==/split_lib_slice_6_apk.apk", zip file "/data/app/com.gomar.gomar_sanidad-xZFFzOUSrlLb9osLbk1xcA==/split_lib_slice_7_apk.apk", zip file "/data/app/com.gomar.gomar_sanidad-xZFFzOUSrlLb9osLbk1xcA==/split_lib_slice_8_apk.apk", zip file "/data/app/com.gomar.gomar_sanidad-xZFFzOUSrlLb9osLbk1xcA==/split_lib_slice_9_apk.apk"],nativeLibraryDirectories=[/data/app/com.gomar.gomar_sanidad-xZFFzOUSrlLb9osLbk1xcA==/lib/x86, /system/lib]]
        at dalvik.system.BaseDexClassLoader.findClass(...

My gradle file:

apply plugin: 'com.android.application'

android {
    compileSdkVersion 28
    defaultConfig {
        applicationId "com.gomar.gomar_sanidad"
        minSdkVersion 21
        targetSdkVersion 28
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'androidx.appcompat:appcompat:1.0.0-beta01'
    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'androidx.test:runner:1.1.0-alpha4'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.1.0-alpha4'
    implementation 'com.google.android.material:material:1.0.0'
    implementation 'com.android.support:appcompat-v7:28.0.0'
}

A sample of my activity_main.xml with the toolbar(Design XML):

    <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".NuevaFicha">

    <android.support.v7.widget.Toolbar
        android:id="@+id/my_toolbar"
        android:layout_width="0dp"
        android:layout_height="?attr/actionBarSize"
        android:background="?attr/colorPrimary"
        android:elevation="4dp"
        android:theme="@style/ThemeOverlay.AppCompat.ActionBar"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:popupTheme="@style/ThemeOverlay.AppCompat.Light" />


    <LinearLayout
        android:id="@+id/linearLayout"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginBottom="8dp"
        android:orientation="vertical"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/my_toolbar"
        app:layout_constraintVertical_bias="0.0">
        ....

I have tried what is said here (Checked ids, Cleaned project, Invalidated caches...) but none of these solutions had the desired results. Do you have any idea?

Thanks in advance.

Answer 1

you are using both androidx and AppCompat hence the error.consider using either.

 implementation 'com.android.support:appcompat-v7:28.0.0' //this is appcompat

    implementation 'androidx.appcompat:appcompat:1.0.0-beta01' //this is android x

you can not use androidx and android support at the same time.
see how to migrate to androidX