Develop Reference

How to fix not found SDK in Android Studio project

I develop one application into Android Studio and when close and open Android Studio.
When open android studio I see red lines with of android studio and not found SDK and I can't write any code!
My Android studio error image :
How can I fix it? please help me

Delete this all four folder's and rebuild againand also check your local.properties file "sdk.dir=/Users/macbookpro/Library/Android/sdk"

Try to clean your project:
Tab Build -> Clean Project

Cannot run my app, asking to select Android SDK

Today I've installed Android Studio Canary 1
Now I cannot run my app. This following dialog appears.
I've already set the right SDK location through File-> Project Structure-> Android SDK location.
Expecting your help to solve this problem.
Warning Dialog image:

Go to project structure settings and set Source Compatibility and Target Compatibility to your current java development kit version:

Just you need to sync your project file with your gradle file.
File -> Sync Project with Gradle Files

I tried every answer in this post but my problem only got resolved when I made these steps:
File -> Close project -> Remove project -> Open existing project (same
project)
Maybe this will save a morning to another person with the same bug.
EDIT
This happened to me a lot on a MacBook. After I posted this answer it just kept happening so what I did was:
uninstall the Android Studio version I had from the App Store;
download the desktop stable version from Android Studio website;
start using the desktop version of Android Studio.
Never happened again.

Sometimes the SDK path will be incorrectly configured. You would need to fix it.
To Settings/Preferences( command + , on mac).
Search for SDK
Under Android SDK, click on edit and point it the root of sdk directory on your file system. (If ther is no SDk installed then install in from the below list).

i suggest you go to build.gradle and sync again.
Or Tools -> Android -> Sync Project with Gradle Files (Android 3+)

You need to insall SDK api 19 check this out.
https://developer.android.com/studio/releases/platforms

Go to sdk manager and install sdk according to your device and check your device api. Example if your device is jellybean then install api 19 sdk.

Go to Tools> Android > SDK Manager and make sure you have selected default Setting under System Setting. In this image I have selected Android 7.1.1 as default SDK

Just click on the button ..."Sync Project with gradle file"
Error will be remove

I had the same problem and what it worked for me was just sync with gradle.
I just did what I've found in this similar question:
How do I "select Android SDK" in Android Studio?
The original answer:
go to build.gradle and click sync now. Then it worked.
Update :
File -> Sync Project with Gradle Files (Android Studio 3.1.1)
Tools -> Android -> Sync Project with Gradle Files (Android Studio
3.0.1) Or You can click on the icon from the toolbar.
Sync Project Icon
This answer may not help works for later version as Android studio Team work on making the tool more better, the way to sync may be
different in the next version of Android Studio.
COMMON WAY that may helps is try to sync project and then Invalidate
Caches and Restart Android Studio.
Solution for Android Studio 3.1.2
Before that, by the way, I had invalidated cache and restarted too, but it didn't work.
Please, try and let us know.
P.S.
I had this problem after I imported a project from Git, just in case someone would like to replicate.

Android studio : when re-import the project it show's error and given a strange floders

while re-importing my project android studio show's plenty of errors
after cleaning and re-importing my project i have got an red circle with “J” on my java files and i'am enable to run my project

Make sure that your gradle version is defined properly.
It seems that this project was on another PC and you imported it on your computer. I think that probably a gradle version conflict occurred and you have two options:
one is to let android studio download gradle version specified in TlaProject (gradle 2.4)
another solution is to edit app level 'build.gradle' file and change its version to a version which is available on your machine (to see which version is available on your system, please check 'gradle' folder inside installation folder of android studio)

My problem was solved by updating the version of android studio .

Android ADT build path issue, how to fix?

I installed android adt with eclipse and appcompat v7 is showing error I tried almost everything i.e
1.change the build path
2.re installing the whole package
3.include the jar files manually
4.Updating the eclipse
Please check for the error in picture.
Please help me its two days I am struggling.

You have installed the higher version of jdk. just follow the below steps.
right click on project properties > click on java compiler, enable project specific settings and change the java version to 1.4 or lower.

If anyone getting the same problem delete appcompat_v4 from the libs folder when creating a new project

Problems with Android Studio - "Please specify Android SDK"

I've just updated to the newest version of Android Studio, and started a fresh, empty project. After finishing the wizard, I opened the main Activity.java file, and there was a message that said:
Gradle project sync failed. Basic functionality will not work properly
I found that I should try the button Sync Project with Gradle Files. This produces another error:
Failed to refresh Gradle project. Could not find any version that matches com.android.support:appcompat-v7:+
Please install the Android Support Repository from the Android SDK Manager
I tried to open the Android SDK manager and got another error:
Please specify Android SDK
So I went into my Project Structure, which has two sections, 'app' and 'Android SDK'. Android SDK points correctly to the Android SDK directory, and app is blank.
What should I do?
I tried downloading the latest SDK bundle and pointing to that in the Project Structure instead, but that hasn't fixed the problem.

I had a similar problem. After updateing to AS 0.4.2 from 0.3.7 I received the error: "Gradle Project sync failed. Basic functionality will not work properly..."
What I did was to delete the content of .gradle folder and modify the gradle-wrapper.properties file:
distributionUrl=http\://services.gradle.org/distributions/gradle-1.9-all.zip
Now it works, I don't know if it's the solution for you, but be sure to backup files before deleting them :)

i know this answer may have been posted before but next time you get such an error after updating sdk,click on file->Invalidate caches/restart. This solution works perfectly for me.