ViewModelProviders.of(activity) 只接受片段或片段活动

Question

我在启动活动中使用 mvvm 并将视图模型与活动相关联时遇到问题，我不会为它创建片段。 在 AppCompatActivity 中：

fun <T : ViewModel> AppCompatActivity.obtainViewModel(viewModelClass: Class<T>) =
    ViewModelProviders.of(this, ViewModelFactory.getInstance(application)).get(viewModelClass)

它说 .of(this,factor) 只接受 fragment 和 fragmentActivity 我已经阅读了链接，但它没有解决我的 build.grable 问题：

apply plugin: 'com.android.application'

apply plugin: 'kotlin-android'
apply plugin: 'kotlin-kapt'

apply plugin: 'kotlin-android-extensions'

android {
    compileSdkVersion 28
    defaultConfig {
        applicationId "com.attendance.myproject.begory"
        minSdkVersion 21
        targetSdkVersion 27
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }

    // to prevent the addition of jvm-target
    kotlinOptions {
        jvmTarget = JavaVersion.VERSION_1_8.toString()
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
    buildFeatures {
        dataBinding true
    }
}

dependencies {
    def room_version = "2.2.3" // check latest version from docs

    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:1.4.10"
    implementation "androidx.recyclerview:recyclerview:$rootProject.recyclerViewVersion"
    implementation "androidx.cardview:cardview:$rootProject.cardViewVersion"
    implementation "androidx.constraintlayout:constraintlayout:2.0.2"
    //noinspection GradleCompatible

    implementation 'androidx.appcompat:appcompat:1.3.0-alpha02'
//room

    implementation "androidx.room:room-runtime:$room_version"
    kapt "androidx.room:room-compiler:$room_version"

    implementation "com.google.android.material:material:1.3.0-alpha03"
    implementation 'androidx.navigation:navigation-fragment-ktx:2.3.1'
    implementation 'androidx.navigation:navigation-ui-ktx:2.3.1'
    testImplementation 'junit:junit:4.13'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
    implementation 'com.google.firebase:firebase-core:17.5.1'
    implementation 'com.google.firebase:firebase-auth:19.4.0'
    implementation 'com.google.firebase:firebase-database:19.5.1'
    implementation 'com.firebase:firebase-client-android:2.3.1'
    implementation 'com.google.code.gson:gson:2.8.5'
    implementation 'me.dm7.barcodescanner:zxing:1.9.8'

    //    Add Zxing library to generate barcode
    implementation 'com.google.zxing:core:3.2.1'
    implementation 'com.journeyapps:zxing-android-embedded:3.2.0@aar'
    implementation "org.jetbrains.kotlin:kotlin-script-runtime:1.4.10"
    //curved bottom navigation
    implementation 'np.com.susanthapa.curved_bottom_navigation:curved_bottom_navigation:0.6.3'

    implementation "androidx.lifecycle:lifecycle-extensions:$archLifecycleVersion"
    kapt "androidx.lifecycle:lifecycle-compiler:$archLifecycleVersion"
    implementation "androidx.core:core-ktx:1.3.2"
    implementation "androidx.lifecycle:lifecycle-viewmodel-ktx:2.2.0"
    implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-android:1.3.9'
    implementation'android.arch.lifecycle:extensions:1.1.1'
}
apply plugin: 'com.google.gms.google-services'

我正在使用 androidx 并且活动是从 appcompatActivitty 扩展的。我在 on create fun 中启动了视图模型。

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_splash)
    if(!Internet.isOnline(applicationContext)) showMessage(getString(R.string.no_internet_connection))

    binding= DataBindingUtil.setContentView(this, R.layout.activity_splash)
    splashViewModel = obtainViewModel()
    binding.splashViewModel
    subscribeToNavigationChanges(splashViewModel)

}

我真的需要几天时间来搜索这个问题，如果有人可以提供帮助，我将非常感激。

Answer 1

问题是您使用了错误的ViewModelProviders导入。 您需要从依赖项中删除此行：

implementation 'android.arch.lifecycle:extensions:1.1.1'

android.arch.lifecycle是旧的、pre-AndroidX 工件，在使用 AndroidX 依赖项时不应该也不能使用。 您已经拥有androidx.lifecycle:lifecycle-extensions依赖项，它是android.arch.lifecycle:extensions的完全替代品，它实际上具有与AppCompatActivity的 AndroidX 版本配合使用的正确版本的ViewModelProviders 。

请注意，没有理由编写或使用任何方法，例如您的obtainViewModel因为这已经由val viewModel: YourViewModel by viewModels()为您提供val viewModel: YourViewModel by viewModels()您的val viewModel: YourViewModel by viewModels() ，它是activity-ktx依赖项的一部分（您已经通过navigation-fragment-ktx作为传递依赖项获得） navigation-fragment-ktx 。