Could not find any version that matches com.android.support:appcompat-v7:30.+.的解决步骤
步骤1：在Android目录中找到Gradle Scripts，选择build.gradle
步骤二：将implementation 'com.android.support:appcompat-v7:30.+'修改成implementation 'com.android.support:appcompat-v7:+'
步骤三：重新加载