我注意到build.gradle文件內容如下：

dependencies?{
????implementation?fileTree(dir:?"libs",?include:?["*.jar"])
????implementation?'androidx.appcompat:appcompat:1.1.0'
????implementation?'androidx.recyclerview:recyclerview:1.1.0'
????implementation?'androidx.constraintlayout:constraintlayout:1.1.3'
????implementation?'com.blankj:utilcode:1.28.0'
????testImplementation?'junit:junit:4.12'
????androidTestImplementation?'androidx.test.ext:junit:1.1.1'
????androidTestImplementation?'androidx.test.espresso:espresso-core:3.2.0'

}

據說AndroidX發布后有些支持發生了一些變化（我也不是很懂）。將第一行復制后appcompat改成recyclerview即可。