adb devices only displays List of devices attached solutions (the phone has been turned on for debugging or there are no other problems)

1. Check the version of adb

Enter in the cmd window to view the adb version, if the version is 1.0.31 or below, it is recommended to upgrade adb

adb version

2. Upgrade adb

Download the adb package: https://pan.baidu.com/s/1SDXFdrv6ddTRVbWFoD7IrA   my package here is 1.0.32, you can also download other higher version packages

After downloading and decompressing, copy the three files in the folder. Paste into the SDK/Platform path to replace the original adb.exe and the other two files with the same name

3. The phone restarts

4. Re-enter adb devices in the cmd window to connect to the phone