Android Studio 无法解析：com.android.support:appcompa

Question

我收到此错误，无法解决：com.android.support:appcompat-v7.28.0.0 我一直在这里查看并尝试将其更改为该行的其他变体，但到目前为止没有运气，为什么我一直收到这个错误？apply plugin: 'com.android.application'android {compileSdkVersion 28defaultConfig {    applicationId "com.example.myapp"    minSdkVersion 15    targetSdkVersion 28    versionCode 1    versionName "1.0"    testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"}buildTypes {    release {        minifyEnabled false        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'     } }}dependencies {implementation fileTree(dir: 'libs', include: ['*.jar'])implementation 'com.android.support:appcompat-v7.28.0.0'implementation 'com.android.support.constraint:constraint-layout:1.1.3'implementation 'com.google.firebase:firebase-auth:11.6.0'implementation 'com.google.firebase:firebase-core:16.0.3'implementation 'com.google.firebase:firebase-database:16.0.1'testImplementation 'junit:junit:4.12'androidTestImplementation 'com.android.support.test:runner:1.0.2'androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'}apply plugin: 'com.google.gms.google-services'