Develop Reference

Android studio: this project is not gradle based project

I have one project which was initially in eclipse, then i managed somehow to convert it to gradle and everything was working fine in Android Studio.
But then i didn't work some time with the project and after few months when i returned to project i am surprised that Android Studio has problems with this project.
When i selected "Android" from top left dropdown in AS, where you should see the project as Android, i saw no files, then i did something and now i see there one empty folder Java.
If i hit button "sync project with gradle files" AS says message as posted in name of question, but it is gradle based project.. there are gradle files etc.
Do you someone know why is this problem? Why it should stop work like this?
Thank you

Make sure you open the project from its root directory. i.e. the directory which contains the top level build.gradle file.
The missing top level gradle file is what causes this error.

For native Flutter Projects:
Note that this error will also appear if you "sync your project with Gradle files " in the root directory. Gradle works only in your android directory (flutter_name/android).
Configure Gradle version
I got this error because i wanted to change some build values like the Gradle version and the Gradle plugin version (and other build values ex. kotlin):
In your current project: File>Open
Select directory: user/StudioProjects/flutter_name/android
Open directory in a new window
After it is opened it will load some packages (see right bottom), which will take some time.
Under File>Project Structure Project you can set the gradle version and under Modules variables of your build
Now you can sync your project with Gradle files or at least read out the error messages, that come with your configuration
After configuration, you might need to restart your project with File>Invalid Caches/Restart....

That worked for me:
copy the file build.gradle
drop the copied file build.gradle in
your app/project folder .

My project stopped showing all of sudden and already had build.gradle file.
I just reopened it via File > Open.

Importing roottools.jar into Android Studio

I'm trying to import roottools from here: https://code.google.com/p/roottools/ (jar file) to the Android Studio project. So far I've tried the following:
copy RootTools-javadoc-3.4.jar into libs directory under my project.
Add imports
Reorganize imports.
Rebuild project
But still I don't have "acces" to it's methods. Is it possible that is only compatible with Eclipse?

I tried using the JAR available for download and it didn't work either. To get this working, I had to download the project available at github here. Compile and run the task "makeJar" (right click on task makeJar in the gradle.build and select run).
I just added this new jar in the libs and referenced in the gradle.build file.
dependencies {
...
compile files('libs/RootTools.jar')
}
or you can add it via Project Properties.
It worked perfectly (don't forget to sync your the gradle files if you edit it manually).

In your project, choose File menu > Project Structure (there's a bug in 0.4.4 and this menu item won't have a title at all; it still works) > Modules > choose your module > Dependencies > + button > File dependency > choose your library from the file picker. That file needs to be somewhere beneath the root directory of your projet; the libs directory is fine.
Screenshot of the Project Structure dialog:

Android Studio not showing modules in project structure

I am using Android studio and I want to add module to my project like
"action bar Sherlock" or jar files,
but when I opened the project structure there is no module or library in the menu :\
In intelij it's appearing:
So what's the problem? How can I add these modules in Android studio?

Update 19 March 2019
A new experience someone has just faced recently even though he/she did add a library module in app module, and include in Setting gradle as described below. One more thing worth trying is to make sure your app module and your library module have the same compileSdkVersion (which is in each its gradle)!
Please follow this link for more details.
Ref: Imported module in Android Studio can't find imported class
Original answer
Sometimes you use import module function, then the module does appear in Project mode but not in Android mode
So the thing works for me is to go to Setting gradle, add my module manually, and sync a gradle again:

First, create your Module. You can do that using the default Android Studio Module Wizard (File -> New -> New Module), select Android Library, give it a Name and a package name, and finish.
After that you will see that nothing happens. Open the side Gradle Projects Section (should be somewhere on the right panel)
You should see something like this:
Expand your module gradle and run the Run Configurations task.
After that refresh the content and refresh the project structure.
It should work now.

Do right mouse click on your project, then select 'Open Module Settings' - then you can add modules to your project..

Go to File->Project Structure-> Project Settings -> Modules.
Click on the green colored + and add new module. select Application module and set the content root to your project module.
Click next and then finish.
Reference

You need to add a gradle.settings file to your root project structure, after that when you "Open Module settings" you will the menu aligned to your gradle.settings. When importing a project to Android Studio, it doesn't create this file for you. Sometimes it's usually better to start a clean project and move your code there, it's usually easier to achieve.

This Might be help some:
To import module as library in your project.
File > New > Import Module
Select Valid path in Source Dir..
Tick on Import > Finish
Now Open Module setting:
Go to File > Project Structure > Modules
Modules > Dependency > click on Green Plus Sign.
Click on Module Dependency > locate module > and Implement your module.
if your module is not shown in "Choose Modules Window"
Follow the below step..
Open Settings.Gradle file
include ':app', 'Put your module name here' and sync project.
Follow Open Module Setting as above.

As for me issue was that the first line in the build.gradle file of the OpenCV library.
It was something like this:
apply plugin: 'com.android.application'
This refers to the fact that the imported OpenCV is an application and not a library. It exists for OpenCV above 4.1.0. So change it to:
Something like this:
apply plugin: 'com.android.library'.
You might get an error in ApplicationId, comment it out in the gradle file.

Open settings.gradle and add the module as below,
include ':app',':bottomnav'
here i have added my newly imported module ':bottomnav' separated with a comma. then Sync your project. your module will be visible to dependency.
Android Studio only displays those module, which are defined in the settings.gradle file of your application.
after defining the module in settings.gradle, you will be able to add the module as dependency of your application.

I had the same problem, after switching to a branch that did not have my module, then switching back.
Clean Project -> Rebuild Project did not work for me.
But File -> Invalidate caches/restart did work.

Check settings.gradle. You'll find this : include ':app'
Just add your own module name and it should look like this :
include ':app', ':yourModuleName'
Sync.
That's it.

Had similar issue when running version control on a project in Android Studio (0.4.2). When pulling it down to a new location and importing the modules, only the "Android SDK" were showing in the Project Structure.
I removed the .idea/ folder from the version control, by adding it to .gitignore file, and did a fresh pull and imported the modules. Now all the settings appeared correctly in the Project Settings and Platform Settings for the Project Structure.

Here's what I did to solve this problem
Close Android Studio
Quick Start -> Check out from Version Control

Please go to Module settings
and choose Modules from Project Settings
then you need to Select src and gen folders and marked them as Source folders by right-click on them and select Source

First You Have To Add Name Of Your Module In setting.gradle(Project Setting) File Like This..
include ':app', ':simple-crop-image-lib'
Then You Need To Compile This Module Into build.gradle(Module app) File Like This..
implementation project(':simple-crop-image-lib')
That's all for adding module now it will be appear in android section or project section as well.
If It's till did't appear rebuild or clean your project..

Although not similar to the question above,
In my case,
The module is not visible in the android tab,
I saw it in the project tab.
After deleting the .idea/workspace.xml file, (I guess there is a problem because the unloadlist list remains here?)
When I reopened the project, it worked fine.
Additionally,
When invalidate caches (clear VCS Log caches and indexes),
It shows up for new modules, not for previously deleted modules (this only worked when deleting workspace.xml).

If you moved the modules, modify your workspace.xml file and settings.gradle file to use the new paths of your module.
Otherwise you will need to try using the import module feature.

Make sure the directory name is lower case.

First and foremost, check that all the modules are listed in your settings.gradle file.
If they are not, add them.
If they are, change something/anything in the file so that the Sync Project prompt comes on. Sync and your project should compile fine; the modules you're looking for will appear in your project structure.

in my case somehow build.gradle file deleted under app i restore it

Android Studio - Importing external Library/Jar

I recently downloaded Android Studio to develop Android applications (I'm coming from Eclipse), and I am having issues using external libraries and/or external JAR files alongside my own project. NOTE: the following tests were conducted on a new application project created from scratch in Android Studio.
Example 1: JAR Import.
Download a fresh copy of the Admobs SDK from Google.
Copy the library jar GoogleAdMobAdsSdk-6.4.1.jar to the project's /libs/ folder.
In the project explorer, right click on the newly added library.jar and click on 'Add as Library'.
Technically at this point everything works, imports work just fine, the layout editor shows a preview of the AdView widget and all that. The only problem is that it doesn't compile successfully.
Log from console:
Gradle:
FAILURE: Build failed with an exception.
* What went wrong:
Execution failed for task ':APITests:compilePaidDebug'.
> Compilation failed; see the compiler error output for details.
* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.
Could not execute build using Gradle distribution 'http://services.gradle.org/distributions/gradle-1.6-bin.zip'.
I tried running gradlew compileDebug --stacktrace, and the problem seems to be that the despite being able to import the classes successfully in both the code & design editor, at compile time, it cannot resolve the imports. Here's the relevant part of the log: (full stacktrace here)
java:6: error: package com.google.ads does not exist
import com.google.ads.AdRequest;
java:7: error: package com.google.ads does not exist
import com.google.ads.AdView;
java:11: error: cannot find symbol
AdView mAdView;
symbol: class AdView
location: class MainActivity
java:22: error: cannot find symbol
mAdView = (AdView)this.findViewById(R.id.adView);
symbol: class AdView
location: class MainActivity
java:23: error: cannot find symbol
mAdView.loadAd(new AdRequest());
symbol: class AdRequest
location: class MainActivity
5 errors
:Test:compileDebug FAILED
But again, the imports work well in the editor, and the dependency is there:
It's also worth noting that without attempting to add a library/JAR, the projects compiles just fine.
I then tried editing the build.gradle file to include the new lib like this:
dependencies {
compile files('libs/android-support-v4.jar', 'libs/GoogleAdMobAdsSdk-6.4.1.jar')
}
This time, it did compile successfully, but the app now forces closes, as apparently, it cannot find a specific class from the lib in the application package.
Caused by: java.lang.ClassNotFoundException: Didn't find class "com.google.ads.AdView" on path: /data/app/com.foo.test-1.apk
Any ideas?

So,
Steps to follow in order to import a JAR sucesfully to your project using Android Studio 0.1.1:
Download the library.jar file and copy it to your /libs/ folder inside your application project.
Open the build.gradle file and edit your dependencies to include the new .jar file:
compile files('libs/android-support-v4.jar', 'libs/GoogleAdMobAdsSdk-6.4.1.jar')
File -> Close Project
Open a command prompt on your project's root location, i.e 'C:\Users\Username\AndroidStudioProjects\MyApplicationProject\'
On the command prompt, type gradlew clean, wait till it's done.
Reopen your application project in Android Studio.
Test run your application and it should work succesfully.

You don't need to close the project and go to command line to invoke grade:clean.
Go to Build-> Rebuild Project

Easy way and it works for me. Using Android Studio 0.8.2.
Drag jar file under libs.
Press "Sync Project with Gradle Files" button.

"simple solution is here"
1 .Create a folder named libs under the app directory for that matter any directory within the project..
2 .Copy Paste your Library to libs folder
3.You simply copy the JAR to your libs/ directory and then from inside Android Studio, right click the Jar that shows up under libs/ > Add As Library..
Peace!

Here is how I got it going specifically for the admob sdk jar file:
Drag your jar file into the libs folder.
Right click on the jar file and select Add Library
now the jar file is a library lets add it to the compile path
Open the build.gradle file (note there are two build.gradle files at least, don't use the root one use the one in your project scope).
Find the dependencies section (for me i was trying to the admob -GoogleAdMobAdsSdk jar file)
e.g.
dependencies {
compile files('libs/android-support-v4.jar','libs/GoogleAdMobAdsSdk-6.3.1.jar')
}
Last go into settings.gradle and ensure it looks something like this:
include ':yourproject', ':yourproject:libs:GoogleAdMobAdsSdk-6.3.1'
Finally, Go to Build -> Rebuild Project

you export the project from Eclipse and then import the project from Android Studio, this should solve your problem, open a eclipse project without importing it from Android Studio you can cause problems, look at:
(Excuse my language, I speak Spanish.)
http://developer.android.com/intl/es/sdk/installing/migrate.html

I had the problem not able to load jar file in libs folder in Android Studio.
If you have added JAR file in libs folder, then just open build.gradle file and save it without editing anything else. If you have added this line
compile fileTree(dir: 'libs', include: ['*.jar'])
save it and clean the project .. In next build time Android Studio will load the JAR file.
Hope this helps.

I'm using Android Studio 0.5.2. So if your version is lower than mine my answer may not work for you.
3 ways to add a new Jar to your project:
Menu under Files-->Project Structure
Just press 'F4'
under Project navigation, right clink on any java library and a context menu will show then click on 'Open Library Settings'
A Project Structure window will popup.
On the left column click on 'Libraries' then look at the right pane where there is a plus sign '+' and click on it then enter the path to your new library.
Make sure the new library is under the 'project\libs\' folder otherwise you may get a broken link when you save your project source code.

I am currently using Android Studio 1.4.
For importing and adding libraries, I used the following flow ->
1. Press **Alt+Ctr+Shift+S** or Go to **File --> Project** Structure to open up the Project Structure Dialog Box.
2. Click on **Modules** to which you want to link the JAR to and Go to the Dependency Tab.
3. Click on "**+**" Button to pop up Choose Library Dependency.
4. Search/Select the dependency and rebuild the project.
I used the above approach to import support v4 and v13 libraries.
I hope this is helpful and clears up the flow.

I use android studio 0.8.6 and for importing external library in project , paste that library in libs folder and inside build.gradle write path of that library inside dependencies like this
compile files('libs/google-play-services.jar')

In Android Studio (mine is 2.3.1) go to File - Project Structure:

Check the libs version requirements. The lib might be trying to call a method from from a higher Android version. Try adding the apps compatability libs.
When all else fails try switching from a Gradle build to an Eclipse build.
Delete and restructure your folders to the eclipse style and delete everything but your code. Then reload the project with your libs.
Once it runs go back to Gradle, if you wish.

java.lang.NoClassDefFoundError - Why? How to troubleshoot?

One of my menu items in my application simply tries to invoke another activity (that belongs to a different project in the same workspace):
myActivity.startActivity(new Intent(myActivity, com.bill.the.App.class));
But that immediately results in an exception at runtime:
E/AndroidRuntime(3847): java.lang.NoClassDefFoundError: com.bill.the.App
Why?
What am I missing?
(the project compiles and build just fine, it's only at run time that this error occurs)

It could be that the project or library containing com.bill.the.App is included in compilation search path, but not included in the resulting apk file (that is deployed to the device). If you include the project or library containing com.bill.the.App using a wrong way, this can happen. Make sure that you include it by using Android Library Project (project properties -> Android) or by including the jar file in the project properties -> Java Build Path -> Libraries.

Just Open your AndroidManiFest.xml, and write following line in it before the </application> tag.
<activity android:name=".App"/>

I had the same problem when importing an old Eclipse/ADT project (made of several projects AKA modules) to Android Studio (2021.3.1.17).
The solution was to right-click the app's module > Open Module Settings > Dependencies > (app's module) > + (Add Dependency) > 3 Module Dependency > Select the module/project that contains the missing class.

The activity may not be registered in the manifest