如何调用“await()”函数？ （未解决的参考错误）

Question

我正在尝试在

中调用await()函数

bookList = bookViewModel.getBookList().await()

在主活动中，但它在标题中给出错误。

主要活动

@AndroidEntryPoint
class MainActivity : ComponentActivity() {

private val bookViewModel: BookViewModel by viewModels()
private var bookList : BookList? = null

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)

    GlobalScope.launch(Dispatchers.IO) {
        bookList = bookViewModel.getBookList().await()
    }

    setContent {
        LOTRAppTheme {

        }
    }
}

}

视图模型

package com.example.lotrapp

import androidx.lifecycle.ViewModel
import com.example.lotrapp.models.BookList
import com.example.lotrapp.repository.BookRepository
import dagger.hilt.android.lifecycle.HiltViewModel
import javax.inject.Inject

    @HiltViewModel
    class BookViewModel @Inject constructor(
        private val repository: BookRepository
    ) : ViewModel() {
    
        suspend fun getBookList() : BookList? {
            return repository.getBookList()
        }
    }

存储库

package com.example.lotrapp.repository

import com.example.lotrapp.models.BookList
import com.example.lotrapp.network.RetrofitApi
import javax.inject.Inject

class BookRepository @Inject constructor(
    private val retrofitApi: RetrofitApi
) {

    suspend fun getBookList() : BookList?
    {
        return retrofitApi.getBookList().body()
    }
}

API

package com.example.lotrapp.network

import com.example.lotrapp.models.BookList
import retrofit2.Response
import retrofit2.http.GET

interface RetrofitApi {

    @GET("book")
    suspend fun getBookList() : Response<BookList>

}

分级：

    plugins {
    id 'com.android.application'
    id 'kotlin-android'
    id("dagger.hilt.android.plugin")
    id("kotlin-kapt")
}

android {
    compileSdk 31

    defaultConfig {
        applicationId "com.example.lotrapp"
        minSdk 21
        targetSdk 31
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
        vectorDrawables {
            useSupportLibrary true
        }
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
    kotlinOptions {
        jvmTarget = '1.8'
        useIR = true
    }
    buildFeatures {
        compose true
    }
    composeOptions {
        kotlinCompilerExtensionVersion compose_version
        kotlinCompilerVersion '1.5.10'
    }
    packagingOptions {
        resources {
            excludes += '/META-INF/{AL2.0,LGPL2.1}'
        }
    }
}

dependencies {

    def compose_version = "1.0.2"
    def lifecycle_version = "2.3.1"

    implementation 'androidx.core:core-ktx:1.6.0'
    implementation 'androidx.appcompat:appcompat:1.3.1'
    implementation 'com.google.android.material:material:1.4.0'
    implementation "androidx.compose.ui:ui:$compose_version"
    implementation "androidx.compose.material:material:$compose_version"
    implementation "androidx.compose.ui:ui-tooling-preview:$compose_version"
    implementation 'androidx.lifecycle:lifecycle-runtime-ktx:2.3.1'
    implementation "androidx.compose.runtime:runtime-livedata:$compose_version"
    // ViewModel
    implementation("androidx.lifecycle:lifecycle-viewmodel-ktx:$lifecycle_version")
    // LiveData
    implementation("androidx.lifecycle:lifecycle-livedata-ktx:$lifecycle_version")
    // Lifecycles only (without ViewModel or LiveData)
    implementation("androidx.lifecycle:lifecycle-runtime-ktx:$lifecycle_version")

    // Saved state module for ViewModel
    implementation("androidx.lifecycle:lifecycle-viewmodel-savedstate:$lifecycle_version")

    // Annotation processor
    kapt("androidx.lifecycle:lifecycle-compiler:$lifecycle_version")
    // alternately - if using Java8, use the following instead of lifecycle-compiler
    implementation("androidx.lifecycle:lifecycle-common-java8:$lifecycle_version")

    implementation 'androidx.activity:activity-compose:1.3.1'
    testImplementation 'junit:junit:4.+'
    androidTestImplementation 'androidx.test.ext:junit:1.1.3'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
    androidTestImplementation "androidx.compose.ui:ui-test-junit4:$compose_version"
    debugImplementation "androidx.compose.ui:ui-tooling:$compose_version"
    //Retrofit
    implementation 'com.squareup.retrofit2:retrofit:2.9.0'
    implementation 'com.squareup.retrofit2:converter-gson:2.9.0'

    //Hilt
    implementation("com.google.dagger:hilt-android:2.38.1")
    kapt("com.google.dagger:hilt-android-compiler:2.38.1")

    //Coroutines
    implementation("org.jetbrains.kotlinx:kotlinx-coroutines-android:1.3.9")
    implementation("org.jetbrains.kotlinx:kotlinx-coroutines-core-jvm:1.5.2")

}

kapt {
    correctErrorTypes true
}

首先，我想从 api 中提取列表，然后在 setContent 中使用可组合函数（使用 LazyColumn）在 UI 中显示它。解决这个错误就足够了，但是如果您有更好的代码建议，我将不胜感激。谢谢！

Answer 1

您似乎不需要在那里调用await()。 getBookList() 直接返回BookList?，所以去掉await() 就可以了。

另外，你说你需要在setContent中使用这个bookList。在这种情况下，您需要将setContent 移动到launch 块中，位于getBookList() 下方。现在setContent 真正在bookList 被获取之前执行。没有setContent的全部内容，很难提供更多细节。