Develop Reference

how to test an app without a USB cable which attaches the device to the debugger?

I'm new to android studio and have just made a new app, which uses position sensors.
All is well when the device is usb connected to the debugger. When I unplug the cable, the app runs fine and I can wave the device around, going to a different room etc. .
But when the app is restarted without that cable, it is "waiting for debugger", which is a little annoying at that point.
I have seen this https://developer.android.com/studio/run#changing-variant but that way I need to sign the app, and I fail on that.
Is there a way to run the app without signing it, and without that debugger cable?
To be more precise in view of the two answers that suggested wi-fi connections (which I can't verify at the moment because the box running AS doesn't have wf-fi connection).
I want to test the app even without debugging, and test it by changing location, too. So I would have to set up a wi-fi connection that would connect to AS over really long distances.
Instead I just want to tell the app (or the device): forget about the debugger.
This: https://stackoverflow.com/a/56541740/4142984 solved my problem.

For the first time you must need to connect device to the android adb and after that you can remove it and still get connection to the android adb.
you should install Android Wifi ADB
you need to connect first time your device with cable in usb debug mode and by using this plugin you can connect your device on the wifi after that you can remove the cable from the system and you will get connected your device to the Android Studio
Note : make sure your system and mobile device must be connected with the same wifi network.

1.Download android-sdk-platform-tools
2. Add the path to environment variables
3. Connect your phone to usb cable
4. Connect your phone and computer in same network(WiFi)\
Now in cmd
5.adb tcpip 5555
6. adb connect *your_phone_ip*:5555
Now you can unplug the usb cable.

Android WiFi ADB plugin not working. Giving error

I installed the Android WiFi ADB plugin to run the app wirelessly. But it's not working it's giving error that Phone and PC should be connected on the same network. I use my phone hotspot to run the internet on my PC. Then I use another phone but then also same error. Someone says it will not work because you use the mobile hotspot for an internet connection on your PC. But when I try to connect another phone then also the same issue. But the same way my friend also does. he also uses the internet using a mobile hotspot but it's working fine on his phone. I have a POCO F1 Phone.

I'm answering this hoping this may help others as well as I find it helpful for my use.
First, Turn on ADB in your phone's developer options. You can search Your_phone_model developer options to find that.
Second, After turning on ADB, Connect your phone with data cable to your laptop/desktop.
Open a Command prompt window, Type adb tcpip 5555, Press allow in adb prompt shown in your phone, it will show restarting adb in tcpip mode. Now, disconnect the USB cable. You can use different port number to connect another device.
Type adb connect your_phone_ip:5555 as for example adb connect 192.168.43.1:5555 in case of hotspot. You can check Phone's IP in WIFI's advanced setting of your phone or in status section.
Now, Everytime your device restarts, repeat steps 3-4.
You can also make a script, just type adb connect your_phone_ip:5555 in a notepad file, save it as name.bat file, right click on it and send to desktop (create shortcut), in the settings on the shortcut, set any shortcut keys. Now, anytime you want to connect, just press the shortcut keys. That's how I do it. You can further open Android studio by this script so it will open Android Studio as well.
Remember, whenever it says Device is Offline, restarts your phone's wifi and reconnect it.

Pair computer and phone with USB cable once, and then always use ADB over WiFi, even after reboot

I'm using scrcpy to mirror the phone screen to computer, which uses adb.
I've followed the steps and it works:
# connect via USB
adb devices
adb tcpip 5555
# now unplug USB, and the following will work over WiFi
adb connect 192.168.1.14:5555
scrcpy
But when you reboot the phone or computer, doing adb connect 192.168.1.14:5555 and scrcpy doesn't work anymore (NB: the phone IP hasn't changed, it's fixed).
Reading the answers from Run/install/debug Android applications over Wi-Fi?, I see 3 options:
plug the USB cable each time before doing a wireless connection, but this is annoying, and somehow reduces the interest of wireless...
Use "ADB over network" (main answer's screenshot), but as noted by many people in comments: "i do not have the "ADB over network" option in debugging option"; so this option doesn't work for me
other techniques that need root (not possible for me)
Question: how to pair the phone and computer with a USB cable only once, and then be able to use adb between them without having to use a USB connection first, after each reboot?
Note: I don't use Android Studio, but only scrcpy.

It's not possible without root the phone. If your phone has rooted. You can use this app. https://play.google.com/store/apps/details?id=com.ttxapps.wifiadb&hl=en. With this app you can easily debugs android apps with only wifi. Don't want USB cable even only first time.

Based on all the information I have the next conclusion. Just for reference, how a low-level setup with changing add routes works inside, described here. It comes up, there is a pretty straight thing inside changing navigation with adb tcpip <port>.
The first thing we need to do, it's setup system property with tcp port with name setprop service.adb.tcp.port (and values with a port number) By default, there is not such property.
And then just restart adb with few commands. stop adbd and start adbd on a device in order to debug bridge listen new port. What is the trick here, that you don't have access to this service and stop/start it without root. But it could be easily done, via Developer setting with stop/start debugging.
This few simple action hidden inside adb tcpip <port>. And the problem, that you cannot change system properties (point 1). That is why all application requires root access, it's just to change the single option. That is why, we need to connect with USB to debug bridge, which can change properties with his sepolicy.
So answering your question. I don't understand either, what is the problem or enabling this small setup in Developer options. But right now, it's possible to do so on some Roms, or devices with root access.

Virtual device running in Genymotion periodically goes offline in ADB

I have an Android device (with Lollipop image, if important) running in Genymotion 2.4 and connect to it via ADB (version 1.0.32) from another developer PC with Eclipse in local network without connectivity problems. All is fine except for periodical drops of ADB connection (other protocols keep working fine), that is ADB loses the device, and when I try to reconnect it says that device is offline. From my experience, this offline status does basically mean that the receiving end (the device) still thinks it's connected and declines new connection. The only method I know to remedy this problem is to restart the device and then ADB connects to it as expected.
If someone is interested, ADB is not running on the remote host machine with Genymotion - otherwise the remove connections from other PCs would be impossible.
The question: how can I refresh "softly" the virtual device to accept new ADB connection without restarting entire device?
P.S. If I leave the "offline" device for its own for some time (quite a long time, for example, for an hour) it seems refreshes its state without external interaction, so ADB is again able to properly connect to and device is reported as "online". But, it makes no sense to wait so long for this to happen. This is just a new piece of information for consideration.

This may not work for you, but has worked for me in the situation where my device simply goes ADB offline. One of the comments on your question mentions that their emulator typically goes offline when their device sleeps. Mine does the same and also goes offline after long periods of inactivity, despite not actually sleeping. Anyway, my fix is plain and simple:
In terminal, navigate to where you have the SDK installed. Then, navigate to the directory platform-tools within your SDK, and issue the following command:
adb kill-server
After that finishes, type this one:
adb devices
That almost always fixes my problem, and I hope it fixes yours as well. Let me know how that works for you.

If you use MacOS Sierra - there is a known bug in it.
28.11.2016 There is no workaround yet except restarting adb which is suggested in #lustig answer.
Google gonna fix it in Android Studio 2.3. Issues to track 82425, 216214
There is no info about will Apple fix it on their side or not.

I need to debug my Android app while not plugged into my computer

So, let me start off by saying that I am 'relatively' familiar and comfortable with making Android apps and using both LogCat and DDMS to debug.
That being said, I'm encountering more of a logistical issue than anything else right now - I am making a locative app, where the GPS is fuelling and controlling other methods in my Activity, and after a while, it is crashing.
Now, because it is locative, I am walking around to test it, in order to receive different GPS locations. Because of this, I am not connected to my computer at the time that it crashes, so have no way (that I know of) to read the stack trace, etc.
In my particular instance, I am navigating through a series of activities, and finally reach the penultimate screen in my app, and while I am running the application in my studio, it runs indefinitely without issue. It is only when I take the device outside that it crashes...
I am wondering if anyone has any tips or tricks with this issue - I'm sure give the prevalence of locative apps, it must have come up, but I cant seem to find the right search terms. It could be as simple as saving the LogCat to file, and/or the stackTrace, but I'm not sure that's the answer...
Thanks in advance.

If I got you right, this is what you are looking for:
https://play.google.com/store/apps/details?id=org.jtb.alogcat&hl=de
Edit: Also there are many more apps like this. You can just browse around in Google Play Store

You can debug the app without rooting your android, unlike the other responses. start off by plugging the android into your computer, then run adb devices to make sure the device is there. Then, run tcpip 5555 to change the android to tcp mode, which will allow debugging over wifi. Disconnect the android from the computer, and connect to it by typing adb 192.168.x.xxx, replacing the x's with your android's IP address. It should connect with no issues, as long as port 5555 is open, and both the android and your computer is on the same wifi.

Simple: Wireless ADB
One of the reason that I choose to run CyanogenMod on my testing devices is that it is a stripped down version of Android that has some additional developer tools, one of those being the ability to access the wireless portion of the ADB system.
As you are probably unaware, you are able to establish an ADB connection to your device over WiFi, however, if running a stock ROM, this requires root access, as it can be potentially harmful to your device, as Wireless ADB will work even over your cellular network, meaning that you could potentially receive apps from other insert carrier here's devices.
If you wish to run WirelessADB, here is a Play Store app that will help you to enable the feature on your device. Requires ROOT
It is as simple as connecting your device to your local WiFi network, (same one the development computer is connected to), enable Wireless ADB, and then running the following command on your computer:
adb connect 192.168.1.101
Replacing 192.168.1.101 with the IP address of your android device.
By establishing this connection, you can run everything just as you would if the device was plugged in via USB Cable.

I recommend ACRA (Application Crash Reports for Android ). It allows you to send crash reports to a number of different destinations. See https://github.com/ACRA/acra/wiki/BasicSetup