com.google.android.material.R Cannot resolve symbol 'R' for BottomNavigationView - r

Question

I use BottomNavigationView in my App, but I have a problem: in BottomNavigationView.java there is import com.google.android.material.R and R is red and write "Cannot resolve symbol 'R'".
The topics I saw couldn't help me.
What would you recommend for me?
The dependencies:
apply plugin: 'com.android.application'
android {
compileSdkVersion 29
defaultConfig {
applicationId "com.example.yourspeakingclub"
minSdkVersion 24
targetSdkVersion 29
versionCode 1
versionName "1.0"
testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
}
}
compileOptions {
sourceCompatibility JavaVersion.VERSION_1_8
targetCompatibility JavaVersion.VERSION_1_8
}
sourceSets {
main {
java.srcDirs = ['src/main/java', 'src/main/java/Models', 'src/main/java/com/salendor/yourspeakingclub/models']
}
}
buildToolsVersion = '28.0.3'
}
dependencies {
implementation fileTree(dir: 'libs', include: ['*.jar'])
implementation 'androidx.appcompat:appcompat:1.1.0'
implementation 'com.android.support:support-compat'
implementation 'androidx.constraintlayout:constraintlayout:2.0.0-beta2'
implementation 'com.google.android.gms:play-services-maps:17.0.0'
testImplementation 'junit:junit:4.13-beta-3'
androidTestImplementation 'androidx.test:runner:1.3.0-alpha02'
androidTestImplementation 'androidx.test.espresso:espresso-core:3.3.0-alpha02'
implementation 'com.google.android.material:material:1.1.0-beta01'
}
The layout:
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="#+id/navigation_container_id"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingTop="?android:attr/actionBarSize">
<com.google.android.material.bottomnavigation.BottomNavigationView
android:id="#+id/navigation_element"
android:layout_width="wrap_content"
android:layout_height="56dp"
android:layout_gravity="start"
android:background="?android:attr/windowBackground"
app:itemTextColor="#000000"
app:labelVisibilityMode="unlabeled"
app:itemIconTint="#color/colorBlack"
app:menu="#menu/bottom_menu" />
</FrameLayout>
The class definition where is the problem with 'R' is available here: https://github.com/material-components/material-components-android/blob/master/lib/java/com/google/android/material/bottomnavigation/BottomNavigationView.java
Thanks

Answer 1

I experienced this problem when I updated Gradle to the latest version. When I returned to version 3.1.3 the error simply disappeared
change this in your build.graddle (project)
classpath 'com.android.tools.build:gradle:3.1.3'

Answer 2

The error should be resolved by doing Alt+Enter & adding the right import. But I'm guessing this issue came out of nowhere after you had already built & run the project at least once (as it once happened with me).
This could be because you're unable to reference the elements of the XML layout. In this case, try:
Build -> Clean project
.
This resolved my issue. Hopefully, it'll help you too :)

Answer 3

I had the same problem.
Simply updated this tool in build.graddle (project) file
classpath 'com.android.tools.build:gradle:4.1.0'
and it worked !!