无法解析 Android Studio 中的符号 'annotation'？

Question

我在我的项目中使用新的 AndroidX，我需要在我的代码中使用 Nullable (@Nullable)，但是，当我尝试 "import android.support.annotation.Nullable;" 时，这个命令 return 给我: "Cannot resolve symbol 'annotation' ".

这是我的 build.gradle 在模块级别：

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])

    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
    // Implementação da autenticação com o servirdor firebase
    implementation 'com.google.firebase:firebase-auth:19.0.0'
    //Implementação da parte visual do Firebase
    implementation 'com.firebaseui:firebase-ui-auth:6.1.0'
    // Implementação de imagens arrendodas
    implementation 'de.hdodenhof:circleimageview:3.0.1'
    // Autenticação geral com o servirdor do Firebase
    implementation 'com.google.android.gms:play-services-auth:17.0.0'
    // Autenticação integrada ao google play services
    implementation 'com.google.firebase:firebase-analytics:17.2.0' // Integração ao Google Análises
    implementation 'com.google.firebase:firebase-messaging:20.0.0'
    // Integração ao sistema de notifação
    implementation 'com.firebaseui:firebase-ui-auth:4.3.1'
    // Integração com o banco de dados
    implementation 'com.google.firebase:firebase-firestore:21.1.1'
    implementation 'com.google.firebase:firebase-storage:19.1.0'
    implementation 'androidx.multidex:multidex:2.0.0'
    // Integração ao sistema de autenticação de usuário
    implementation 'androidx.legacy:legacy-support-v4:1.0.0'
    implementation 'androidx.navigation:navigation-fragment:2.1.0'
    implementation 'androidx.navigation:navigation-ui:2.1.0'
    implementation 'androidx.lifecycle:lifecycle-extensions:2.1.0'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'androidx.test.ext:junit:1.1.1'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'
    implementation 'androidx.work:work-runtime:2.2.0'
    implementation 'androidx.appcompat:appcompat:1.0.0'
    implementation 'com.google.android.material:material:1.0.0'

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

Answer 1

不要混用 android 支持 和 androidx.

对于 androidx，使用 androidx.annotation.Nullable

Answer 2

因为我在 the official documentation 上找到了信息您需要迁移到 Androidx。要找到映射到此已弃用 class 的 AndroidX class，请参阅 Class Mappings

上的 AndroidX 支持库

因此，将 android.support.annotation.Nullable 替换为 androidx.annotation.Nullable。

无法解析 Android Studio 中的符号 'annotation'？

Cannot resolve symbol 'annotation' in Android Studio?

android

build.gradle

android-gradle-plugin

androidx