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Cannot resolve symbol 'androidx.constraintlayout.widget.ConstraintLayout'

Cannot resolve symbol 'androidx.constraintlayout.widget.ConstraintLayout'
I made an empty activity in Android Studio, ahead of nothing added, in activity_main.xml, there were so many red lines,and the prompt was: Cannot resolve symbol'
while, these code was generated by Android Studio, I tried file->invalidate cashes/restart... and installed all the SDK tools but Google series. The error was still there.
Gradle was successful, and JDK was installed.
Has anyone a solution ?

Make sure constraint layout is updated to latest version:
implementation 'androidx.constraintlayout:constraintlayout:2.0.0-alpha3'

This is because your project support android legacy version, check this out in build.gradle, search for this key:
implementation 'com.android.support:appcompat-v7:28.0.0'
If confirmed, you should use the compatible version instead of the androidx version.
That is android.support.constraint.ConstraintLayout.
BTW, are you trying to follow the https://developer.android.com/guide demo? This tutorial sucks.

'javax.annotation.processing does not exist; cannot find symbol class Generated' despite adding dependecy into build.gradle

I wanted to contribute to one app, but when I set my IDE up and wanted to build the project, compiler thrown an error javax.annotation.processing does not exist; cannot find symbol class Generated. I've searched Google for the problem, people was suggesting to add compileOnly 'org.glassfish:javax.annotation:10.0-b28' to the main.gradle file, but author included such line already. I have turned Annotation processing on in IDE settings already. Dev said today that he can compile project. I have no idea, what's going wrong?
Maybe it's connected to the fact, that he's using Android Studio, and I - IntelliJ IDEA? But, as said by JetBrains here, that shouldn't matter, as Idea has all of the features of Android Studio. Both IDEs are up-to-date.

I had to face the same issue. I found the solution somewhere and it resolves the problem. Add the below line in build.gradle file.
implementation 'org.glassfish:javax.annotation:10.0-b28'
compileOnly 'com.github.pengrad:jdk9-deps:1.0'

Android studio automatically tries to update libraries?

In my project I have many libraries defined in dependencies section in gradle. Problem is once in a while (once/twice a day)Android Studio gives me errors like this when opening the project or trying to get a release output:
Error:Unable to resolve dependency for ':TMessagesProj#armv7Debug/compileClasspath': Could not resolve com.google.android.gms:play-services-gcm:11.2.+.
My guess is it is because build tools is trying to check if there is an update for each library and when it doesn't find an Internet connection, it shows this error. If so, how can I change the setting in a way it doesn't have to check for updates? In other words in my project I don't need to update my libraries.
I know there is an offline mode that will probably do the trick! But I don't want to use this feature because it will probably disable some other useful features too. I just want to prevent it from automatically checking for library updates(If that's the problem shown above).
I included some part of my dependencies in gradle here:
dependencies {
compile 'com.google.android.gms:play-services-gcm:11.2.+'
compile 'com.google.android.gms:play-services-maps:11.2.+'
compile 'com.google.android.gms:play-services-vision:11.2.+'
compile 'com.google.android.gms:play-services-wallet:11.2.+'
}

Dependencies with a plus like 11.2.+' will always lead to repeated builds.
You have to specify the full version like:
com.google.android.gms:play-services-gcm:11.2.0
If you do not specify gradle will always be building because its looking for the latest version online of 11.2.+ may be 11.2.4, 11.2.6 etc

How to fix "Rendering Problems The following classes could not be instantiated"?

I just started learning android coding and I keep getting this error:

Add these support library in build.gradle and also make sure the version of the support library(goto sdk manager and get the version number of sdk platform and place it in below dependancy because version of support library and sdk platform should be matched)
compile 'com.android.support:appcompat-v7:23.3.0'
compile 'com.android.support:design:23.3.0'

Try any of the following
Click refresh button on the preview pane
Sync Project with Gradle files
Click Tools > Android > Sync Project with Gradle Files
Rebuild Project
Click Build > Rebuild Project

This seems to come up periodically with Android Studio and it happened again today on an install I haven't used in a while. There may be more than one solution, but as of today June 08, 2016, I made sure two things are set:
1) Make sure you're on SDK/API 23 (or lower if necessary) vs the N preview, and
2) change the theme to "App theme". You may have to choose "Manifest Theme" in the left column before you can see "App Theme" show up as an option in the right column.
3) hit the refresh button (looks like two arrows in a circle)
Referring to a post above, both the support.appCompat and support.design libraries should be automatically added as dependencies to the gradle file, but you can double check them if necessary (and get the newest ones if the versions have changed).
You should see both of these:
compile 'com.android.support:design:23.4.0'
compile 'com.android.support:appcompat-v7:23.4.0'
Why Google and Jet Brains can't keep this from happening I don't know, but as of today, it cleared the problem right away.

The following classes could not be found: - android.support.design.widget.TextInputLayout

This is Tutorial which i am following.
Please help me out from this error. Rebuild is not solving the problem.

Does your build.gradle file contain the line below?
compile 'com.android.support:design:22.2.0'

You must include support libraries (like the ones below), yet this is sometimes not sufficient.
compile ("com.android.support:support-v4:23.3.0")
compile ("com.android.support:appcompat-v7:23.3.0")
compile ("com.android.support:support-annotations:23.3.0")
compile ("com.android.support:recyclerview-v7:23.3.0")
compile ("com.android.support:design:23.3.0")
Examine your layout in design view, and click on Show Exception
This answer will help if you have the following problem:
You need to use a Theme.AppCompat theme (or descendant) with the design library.
In your Manifest file, include in your application declaration
android:theme="#style/Theme.AppCompat"
Rebuild and your problem should be solved.

First things first :
If you are using the lastest sdk28 TextInputLayout is having some bug. At least mine did (date: 22 Sept 2018 ) NOT work.
To make it work the best way is to use slightly lower SDK for you target and compile SDK version. (I used sdk 27 and everything worked out fine then.)
To use TextInputLayout and then its features such as "floatinghinttext" you need to update your build.gradle(module.app) found in gradleScripts.
in dependencies add-
implementation 'com.android.support:design:25.0.0'
(if you get some error it must be of some latest version available, so use that instead of 25.0.0)
Note: The "compile" keyword is getting replaced by "implementation" for newer/all versions.
I am fairly new to android development, suggestions are welcomed. Please excuse if any mistakes committed.