download a demo that looks like this

1 first check if gradle downloaded

if the following text prompt is not downloaded, it may be caused by a network problem

Gradle sync failed: Connection timed out: connect. If you are behind an HTTP proxy, please configure the proxy settings either in IDE or Gradle.

2 first checks if the androidmanifest.xml configuration file is missing the interface pointing to

if you’ve done both of those things, and you haven’t done them properly, then restart it and take a look at

3 restart

, in general the most likely problems are 1 and 3,