This error occurred while I was working on Gradle sync in Android Studio. The Android Studio error prompt was Gradle sync failed: A problem occurred configuring project': app', and the last lines of the error log were like this.

2018-10-30 21:05:30,041 [thread 106]   WARN - ect.sync.idea.ProjectSetUpTask - A problem occurred configuring project ':app'. 
2018-10-30 21:05:30,041 [thread 106]   INFO - e.project.sync.GradleSyncState - Gradle sync failed: A problem occurred configuring project ':app'.

Consult IDE log for more details (Help | Show Log) (379 ms) 
2018-10-30 21:05:30,044 [e-1136-b06]   INFO - idea.project.IndexingSuspender - Consuming IndexingSuspender deactivation event: SYNC_FINISHED 
2018-10-30 21:05:30,044 [e-1136-b06]   INFO - idea.project.IndexingSuspender - Finishing batch update for project: Project 'D:\Projects\AndroidApplication' AndroidApplication 
2018-10-30 21:05:30,113 [thread 107]   INFO -       #com.jetbrains.cidr.lang - Clearing symbols finished in 0.022 s. 
2018-10-30 21:05:30,113 [thread 107]   INFO -       #com.jetbrains.cidr.lang - Building symbols in FAST mode, 0 source files from total 0 project files 
2018-10-30 21:05:30,114 [thread 107]   INFO -       #com.jetbrains.cidr.lang - Loading symbols finished in 0.000 s. 
2018-10-30 21:05:30,114 [thread 107]   INFO -       #com.jetbrains.cidr.lang - Loading Header Maps finished in 0.000 s. 
2018-10-30 21:05:30,114 [thread 107]   INFO -       #com.jetbrains.cidr.lang - Loading Module Maps finished in 0.000 s. 
2018-10-30 21:05:30,115 [thread 107]   INFO -       #com.jetbrains.cidr.lang - Saving Module Maps finished in 0.001 s. 
2018-10-30 21:05:30,115 [thread 107]   INFO -       #com.jetbrains.cidr.lang - Loaded 0 tables for 0 files (0 project files) 
2018-10-30 21:05:30,115 [thread 107]   INFO -       #com.jetbrains.cidr.lang - Building symbols for 0 source files 
2018-10-30 21:05:30,118 [thread 107]   INFO -       #com.jetbrains.cidr.lang - Building symbols for 0 unused headers 
2018-10-30 21:05:30,119 [thread 107]   INFO -       #com.jetbrains.cidr.lang - Building symbols finished in 0.004 s. 
2018-10-30 21:05:30,120 [thread 107]   INFO -       #com.jetbrains.cidr.lang - Saving modified symbols for 0 files (0 tables of total 0) 
2018-10-30 21:05:30,120 [thread 107]   INFO -       #com.jetbrains.cidr.lang - Saving symbols finished in 0.000 s. 
2018-10-30 21:05:41,361 [e-1136-b06]   INFO - idea.project.IndexingSuspender - Consuming IndexingSuspender activation event: SYNC_TASK_CREATED 
2018-10-30 21:05:41,375 [e-1136-b06]   INFO - e.project.sync.GradleSyncState - Started sync with Gradle for project 'AndroidApplication'. 
2018-10-30 21:05:41,377 [e-1136-b06]   INFO - idea.project.IndexingSuspender - Consuming IndexingSuspender activation event: SYNC_STARTED 
2018-10-30 21:05:41,377 [e-1136-b06]   INFO - idea.project.IndexingSuspender - Starting batch update for project: Project 'D:\Projects\AndroidApplication' AndroidApplication 
2018-10-30 21:05:41,388 [thread 107]   INFO - s.plugins.gradle.GradleManager - Instructing gradle to use java from E:/AndroidStudio/jre 
2018-10-30 21:05:41,391 [thread 107]   INFO - s.plugins.gradle.GradleManager - Instructing gradle to use java from E:/AndroidStudio/jre 
2018-10-30 21:05:41,398 [thread 107]   INFO - xecution.GradleExecutionHelper - Passing command-line args to Gradle Tooling API: -Didea.version=3.2 -Djava.awt.headless=true -Pandroid.injected.build.model.only=true -Pandroid.injected.build.model.only.advanced=true -Pandroid.injected.invoked.from.ide=true -Pandroid.injected.build.model.only.versioned=3 -Pandroid.injected.studio.version=3.2.0.26 -Pandroid.builder.sdkDownload=false --init-script C:\Users\xxxx\AppData\Local\Temp\ijinit.gradle 
2018-10-30 21:08:38,848 [e-1136-b06]   INFO - ide.actions.ShowFilePathAction - 
Exit code 1 

After searching the Internet for a circle, I did not solve the problem. Finally, I put my eyes on this': app'. I noticed that there was a file named settings.gradle in the project. When I opened it, its content was include d': app'. I added an English sentence before this app with the attitude of a dead horse and a living horse doctor. I didn't expect sync to succeed after that. It was very happy and crying!

(Whisper Ratio: Android Studio is really the worst IDE I've ever used. It's rare for Android SDK to have trouble configuring, downloading files, and compiling errors.)