Android Studio - Device is connected but 'offline'

问题

This is quite a common question, but none of the solutions appear to work for me. First time asker, so apologies if I get the conventions wrong.

I am trying to connect my Galaxy S5 to my computer running Ubuntu 14.04 so I can do some android development. I have recently downloaded and installed Android Studio and the SDK and my device is detected when it's connected via USB but the device either appears as 'unauthorized' or 'offline'. I know I should be expecting the RSA key prompt but this never appears.

I have tried:

Checking debugging was enabled
Running adb kill-server and adb devices
Restarting (the device, developer options, the machine)
Simple unplugging and replugging the USB cable
Checking my adb version (it is 1.0.31)
Trying different USB ports
Revoking USB debugging authorizations
Toggling enabling ADB Integration from within Android Studio
Connecting as PTP device and MTP device

I have tried it on a separate machine that runs fedora and this works fine with no issues, the promopt appears right away. Therefore I imagine it is not the USB cable that is faulty.

Any ideas?

回答1:

Try these:

Unplug and replug the USB cable.
If it still doesn't work, unplug the USB cable, disable then enable USB debugging in the device settings.
If the above two methods fail, reboot the device.
If rebooting the device also fails, reboot Android Studio too.
If reboot Android Studio still fail, try adb kill-server then adb start-server

Hope this helps.

回答2:

Try killing adb adb kill-serverthen disable usb debugging and then start adb by adb start-server then enable usb debugging and plug phone again and huh don't let phone sleep between process

EDIT

There turned out to be a problem with my laptop's ADB RSA key. I'm assuming my G3 was rejecting a bad key and disallowing my laptop to connect to it via ADB.

ADB saves a key file in one of multiple places on a Windows computer, the first is in the location where adb.exe is (C:\android), the second is in the user's >profile (C:\Users*username*.android), the third place is in the Windows system files (C:\Windows\System32\config\systemprofile.android), the file is >simply named "adbkey" with no extension. If there is no key file when ADB runs, it will generate one automatically.

Mine was located in my user folder (C:\Users*username*.android). All I had to do was delete the adbkey file (there was also a file named "adbkey.pub" which >I deleted as well), restart the adb server in command prompt (adb start-server) and plug my phone in. I instantly received the RSA Fingerprint Key window on my >G3 allowing connection between the two devices. Then typing "adb devices" returned my phone's serial number followed by "device" showing it was available. >I went back to the C:\Users*username*.android\ folder and sure enought there were new "adbkey" and "adbkey.pub" files.

got from XDA

EDIT 2

TRY this steps too

Navigate to where .android is stored
open .android and delete file named as adbkey and adbkey.pub
Start ADB then typeadb kill-serverand adb start-server

回答3:

My fix to this issue:

Android settings
Developer options
Revoke USB debugging authorizations
Replug in device and accept authorization as usual.
Profit

回答4:

Step 1: Turn off USB DEBUGGING in Developer Options

Step 2: Remove USB Cable

Step 3: Turn on USB Debugging(This rests USB Configurations)

Step 4: on Command Prompt enter adb kill-server and then adb start-server

Step 5: Connect the USB Cable

Step 6: Check Devices connected in Run in Android Studio(you should be able to see your device listed)

Step 7: If you want to continue running using the cable this would be good enough

(If you want to do Wireless Debugging continue with below step)

Step 8: type adb tcpip 5555. If no error is displayed remove USB Cable

Step 9: Look up IP Address of your phone from About abd then type adb connect xxx.vvv.b.n(your phone's IP)

Step 10: Check in Devices in Android Studio again and you shud see you r device in List of devices. If yes,

回答5:

If you are on windows and you encountered the same problem, try to kill the adb.exe process from task manager and then try to run your app again.

回答6:

Could not get Samsung Note II (N7100) to connect.

Step 1. Follow answer from user4847410 above. Next time you connect your phone it will come up with an authorisation message and you're in.

Step 2. I also swapped my cable.

Step 3. Check USB port as if you install on one particular port then another port may not be ok for you.

Note: made two batch files

adb-fix.bat

adb kill server
adb start server
pause

adb-devices.bat

adb devices
pause

-- voted for that correct answer but I don't have enough kudos so it was removed! --

回答7:

I had a long white cable. Just wouldnt stay connected. Switched to another, shorter, black cable and it works 100% of the time.

回答8:

A shorter cable did the trick.

It turns out that the wire thickness used inside the cable impacts on the resistance of the cable assembly – this resistance causes energy loss inside the cable when an attached load draws a current, and causes a voltage drop which can reduce the voltage to the end device to a point where it is not possible to charge quickly or completely.

http://goughlui.com/2014/10/01/usb-cable-resistance-why-your-phonetablet-might-be-charging-slow/

回答9:

Change the USB cable !!!! I can't explain this technically, however after a lot of trial and error, this what have worked for me.

回答10:

Disabling and Enabling the Developer options and debug mode on the Android phone settings fixed the issue.

回答11:

You can try this:

Go to tools/enable adb integration and uncheck it.
now check it and run again. Next time, android studio will restart adb and it may find your device.

回答12:

Restart adb by issuing these commands in cmd

adb kill-server to kill existing adb session

followed by adb start-server to start a new adb session
Disable and re-enable USB debugging on the phone and accept RSA fingerprints if asked by phone
Rebooting the phone if it still doesn't work.

If all above don't solve your problem, you may try delete environment variable named "ANDROID_SDK_HOME". It really solved my problem. Hope it Help you!

回答13:

To fix this, use USB2 instead of USB3

回答14:

This problem is because you have used an old adb version and not support on your device. or you have more than one adb

The key is:

make sure you have a latest adb executable on your SDK
Make sure to run adb command from "SDK_DIR/platform-tools/" because this should be the latest version (type command "which adb" to check) if u have more than one adb file, you can rename another one.

in my case, on my Windows 7 i have one more adb on "C:\Windows\adb.exe" and its an old version, so my adb command always run from that file. I fixed the problem by running adb form my sdk directory "SDK_DIR/platform-tools/adb.exe"

回答15:

On windows--> Launch your terminal from the platform-tools folder inside android sdk.

Then use the following commands

adb kill server
adb start server

it should work

回答16:

Earlier for almost 3hrs I did:

I tried everything given in several sites and my android device never came online.
when I was running adb kill-server and then adb-startserver the "Device File Explorer" on the right bottom of the android studio showed "Device is not online (DISCONNECTED)".

Here is how solve this:

Revoked all USB debugging authorization on the device under "Develop options"
And I added sudo to command "sudo adb kill-server" and then " sudo adb start-server".
After this the message in "Device File Explorer" in android studio changed to "device is pending authentication please accept debugging session on the device". But no message appeared on the device. Tried stopping-restarting adb, connect reconnet usb cable, stop-start usb debugging but nothing worked.
Went back to device and changed the device usb settings from usb charging to "PTP", and, restarted the Android studio. And, boom, the message appeared on the phone to accept the debugging session on device.

回答17:

Try upgrade your Android SDK Platform as below steps:

Run the SDK Manager
Execute "Install packages…"
Restart the SDK Manager

I tried and it's ok for me.

ref: link

回答18:

You maybe having an older version of the ADB, Update the tools package and that should bring down the latest ADB.

回答19:

I also recently had this problem and I solved it by rebooting Android Studio. But my friend had to have the original cable for his device, no other cables worked.

回答20:

In my case (same problem - that Nexus 5 is connected but with "offline" status) the problem was solved by "Invalidate caches and Restart" in Android Studio. Suppose that problem was in adb and restarting Android Studio causes to adb restart.

回答21:

Download and Install your device driver manually through visiting manufacturer website like :Samsung,micromax,intex etc.

回答22:

In my case the problem was that I used a USB extension cable. As soon as I plug the microUSB cable right into the PC the device has detected.

回答23:

In my case, turned out that you need to be logged as owner of device to properly accept the USB debugging.

Tried the "Disable and re-enable USB debugging on the phone" step but didn't get the RSA prompt on "normal" user, switched to owner and tried again and got it.

回答24:

I had this issue on a device with USB-C using a microUSB cable with a USB-C adapter. After switching to a USB-C cable without any adapter it worked. I only saw this issue on a LeEco.

回答25:

I tried most of the things on this page and none of them worked for my Samsung S5. However, when I switched the cable to a USB-C type the problem seemed to be solved...until next time.

回答26:

Besides the solution mentioned above, try to download Samsung's Android USB Driver for your platform. Here is a link to the Windows one:

https://developer.samsung.com/galaxy/others/android-usb-driver-for-windows

回答27:

If your app doesn't manipulate WiFi connections - another slightly different solution, which bypasses USB issues entirely - enabling a wireless debugging connection - ADB over WiFi/TCP/IP.

回答28:

use this command

-> adb disconnect

-> adb connect <ip address for your mobile:port number>

Eg : adb connect 192.168.2.58:5555

回答29:

Reboot the your mobile this will fix it.

来源：https://stackoverflow.com/questions/30964854/android-studio-device-is-connected-but-offline

标签

android-studio

adb