Android Studio
Q1：
Gradle '×××' project refresh failed.
re-download dependencies and sync project (requires network)
It basically means that the gradle zip file in the cache folder is corrupted, if you don't want to change the version like the up-voted answer
then you must delete the folder for your gradle version you're using for this project from the below path.
Then just retry the sync and android studio will download it again
C:Users [user here] .gradlewrapperdists
ex: if you're using 3.3 for this project you'd be deleting the folder
C:Users[user here].gradlewrapperdistsgradle-3.3-all
Q2：
Installation failed with message Failed to install all.
It is possible that this issue is resolved by uninstalling an existing version of the apk if it is present, and then re-installing.
WARNING: Uninstalling will remove the application data!
Do you want to uninstall the existing application?
Again in this issue also I found Instant Run buggy. When I disable the Instant run and run the app again App starts successfully installing in the Device without showing any error Window. I hope google will sort you these Issues with Instant run soon.
Steps to Disable Instant Run form Android Studio
File > Settings > Build,Execution,Deployment > Instant Run > Un-check (Enable Instant Run to hot swap code)
IntelliJ IDEA
Q1：Maven projects need to be imported: Import Changes Enable Auto-Import
Select this check box, if you want IntelliJ IDEA to perform reimport automatically each time you change your pom.xml.
From the documentation.
In other words it just automatically updates project details upon POM change. Generally it tells IDEA that, for example, dependencies for those new external classes you started using in your code can be found in updated version of POM.
Here are some information about it aswell.
设置
N1：鼠标悬停文档提示设置
Setting - Editor - General - 勾选show quick documentation on mouse move