Develop Reference

Ctrl+V does not work in IntelliJ

A while ago, Ctrl+V stopped working in Intellij IDEA. Neither the shortcut nor Edit > Paste works. It's really weird, since "Paste Simple" still works fine, so does Ctrl+C and Ctrl+X.
I've seen a lot of suggestions to solve this problem, but most of them are somehow related to the Vim Emulator for IntelliJ, which I don't use. I tried to play around with the Keymap, but could not get it to work.
I'm using Intellij 2017.2.5 on Windows 10. Maybe I screwed it up myself somehow, but I wish to fix it, because it's really painful to work without Ctrl+V.

You can try alternatives:
Ctrl + Shift + V for Windows or Linux
or
You might try Ctrl+INS for copy and Shift+INS for paste and
see if they work. They are the traditional cut and paste and have been
around a lot longer than Ctrl+c/Ctrl+v

I had the same problem, I regularly reboot so I always have a back-up of my settings. When I reimported them and updated the plugins I could paste again without issues.
Back-up your settings from a working state File>>Manage IDE Settings>>Export Settings and use >> >>Import Settings to apply them.
If you don't have a back-up you can try it, but you might be backing up the problem as well. In that case you will have to reset to defaults and reset the IDE to your liking.

My OS is Ubuntu 18.04, and i had this problem before. An effective solution for my IDE is to set the Keymap to Default, which is file>setting>Keymap.

JDK is not defined on Android Studio start

From 2 days, when I open Android Studio project, it seems like JDK is not defined, like on picture. When I place mouse cursor on some red method and click alt + enter, I can setup JDK, but when I make it, it does not help at all. Even Gradle refresh gives nothing.
I can temporarily fix this by going to "Invalidate caches/Restart...", but then upon the next restart I see the same problem.
Android Studio Version: 2.3.3
Edit

ADT Eclipse SDK troubles - No DDMS found

Please help me, I'm having serious trobules with Eclipse for the second time.
I'm following a guide and in these last days my Eclipse used to work fine (and was heavy 600 mb), now after the updates I did recommended by the guided, it downloaded a lot of things for hours and my folder now is 12.6 GBs (and it's pretty uncofortable since I'm on a not too large SSD).
The problem is that the old ADT worked, after the update every project gives errors, like there is no Android SDK.
The console gives me this error
[2014-11-18 22:37:33 - DDMS] DDMS files not found: C:\Users\Ruggiero\Desktop\Ruggiero\android_dev_environment\sdk\tools\hprof-conv.exe
If it can help you, when I run Eclipse it shows me this error message
Now, the most obvious thing would be "just press Check for updates".
When I do it, it says me there are no updates.
So I go for "Install new software" and after I go to the link (official Google link) and try to install the updates it gives me this error
error2 http://s7.postimg.org/h5r1gaa63/eclipseerror2.png]
Please do not flag as duplicate as I already searched on the web and StackOverflow too and even if I found similar troubles, no one was equal or really close to mine.

I had a similar problem. The only way I could make it work was to completely uninstall Eclipse and Android SDK and reinstall again.

There are likely workarounds for this, but I think I suggest just downloading a fresh Android bundle (with all the correct updated software), and install it fresh.
I have had experiences where something goes wrong in the tools update, and found the simplest way to correct is to uninstall my existing tools and start fresh. It is easy to install the bundle, and you will know you have all the correct packages and software installed.
You will spend a bit of time trying to debug your install, it will be quicker to install a fresh instance.

I self resolved by switching to Android Studio IDE

Update ADT from 21.0 to 21.1

i downloaded APIs 15,16 and 17. After the download is finished, I closed eclipse but when i open it again it gives me a message box saying I need to update my ADT from 21.0.0 into 21.1 or higher, (and my current project suddenly didnt work, and full of red lines). There is a "Check for Updates" button. But after clicking it, it says there was no update found. I asked Google and found out that there is already ADT 21.1 released. I am wondering if I should just download the latest ADT bundle, but also looking for a quicker solution. I said “quicker” because my internet connection is a bit slow. :( It will take me a whole day to finish the download. :( And also after i downloaded the API, my graphical layouts do not show any more. There is a message saying "Eclipse is loading the SDK. Home.xml will refresh automatically once the process is finished." I waited for eternity, but nothing shows up. Im pretty messed up here. My project does not work anymore, although it worked well before i downloaded the APIs. Can anyone help me?. Thanks.

Go to eclipse > help > Check for updates.
It should list the latest update of adt. If it doesn't work, try this :
go to eclipse > help > Install new software
Click on add
add this url : https://dl-ssl.google.com/android/eclipse/
It will list the updates available- which should ideally be adt 21.1.0 (latest)
install the latest adt and everything should be fine.

The same thing happened to me, here's what I did-
Apparently, the SDK updated to version 21.1, but ADT, still at 21.0. 21.1 is currently a preview release (so I'm not sure how we accidentally updated the sdk...), so you have to manually add the update source. There's a nice guide (http://tools.android.com/preview-channel), but here's what you need:
Start Eclipse, then select Help > Install New Software.
Click the "Add" button, in the top-right corner.
In the Add Repository dialog that appears, enter "ADT Previews" for the Name and the following URL for the Location:
https://dl-ssl.google.com/android/eclipse-preview/
Click OK.
If you have trouble acquiring the plugin, try using "http" in the Location URL, instead of "https" (https is preferred for security reasons).
In the Available Software dialog, select the checkbox next to Developer Tools and click Next.
This worked for me, although I would rather have just downgraded the sdk.
Hope I helped!

go to window -> SDK manager and then install Android SDK Tools to 21.1 and then check for updates again.
I used to get error " update cannot be installed " for that run eclipse in Admin permission.

same with your problem !!!
btw, Thanks for the info ! I tried it after read this and wohooow It worked ! thx
go to eclipse > help > Install new software
click on add
add this url : https://dl-ssl.google.com/android/eclipse/

Application no longer works in lower android versions after setting android:targetSdkVersion

After I set android:targetSdkVersion to 15, application doest work in 1.6 emulator.
It throws java.lang.VerifyError.
Edit:
The app is crashing because I'm calling invalidateOptionsMenu, which came in API 11. Now even I check before calling it (if (VERSION.SDK_INT >= 11)). It still throws same error.

You probably forgot to set your project build to version 4.0.3.
Right click your project in the project explorer.
Click properties.
Click Android.
Click the check box next to 4.0.3.

Just set up a new emulator!
For this you can simply use your AVD Manager (Android Virtual Device)!
It's like as you would run your 4.0 App on a 1.6 Device.
If you don't have to set your apiLevel to 15 (i.e. you don't need the new APIs) you should think about setting it to the lowest level possible.
Edit:
There IS a difference between the minSDK Version and the API level of the project:
MinLevel: what devices are able to run the app
ApiLevel: what APIs are able to use in your project in eclipse
Try to make sure you don't mix them up, so that your MinLevel hopefully matches your ApiLevel. Doing so will ensure your App does not get such errors,

Nice trick in this answer. Brilliant. Thanks everyone.