Turn on android debugging My phone screen is completely broken and good thing is that its debugging mode is on and I can access my phone screen using Vysor on a PC
but I have another PC and when I trying to access my phone with that system I have to grant access with OK button but I cant do that so how can I access my phone screen on different PC or grant debugging?

Phone's screen is broken
USB debugging is on
I Need to grant access to debugging prompt dialog
This guide assumes that USB debugging was enabled on your device before you broke it. You can enable USB debugging via a custom recovery, such as twrp, using:

adb shell
echo "persist.service.adb.enable=1" &gt;&gt;/system/build.prop
echo "persist.service.debuggable=1" &gt;&gt;/system/build.prop
echo "persist.sys.usb.config=mass_storage,adb" &gt;&gt;/system/build.prop"
reboot


This method was used to bypass the secure USB prompt on a Galaxy SII with a shattered screen. I think it may work on another device too...

For this to work, you need another device running Android 4.4.2 or above with USB debugging enabled and the same computer authorised from that device. i.e. connect that device to your computer and press "OK" on the authorisation prompt that appears on screen for secure USB debugging. Let us call this device the authorised device.

adb_keys is the file we need from the authorised device which is located in /data/misc/adb/
Normally you must be rooted to take the adb_keys file from the device using Root explorer or ES File Explorer,  but let's assume that the authorised device is unrooted. You don't need to root it. However, if your authorised device is rooted then simply copy the adb_keys file on your computer and jump directly to Step 3.

Steps:


Connect the authorised device to your computer using USB (debugging enabled) and open a command prompt with administrator privileges (Minimal ADB &amp; Fastboot is perfect here).
To get the adb_keys file, use this command:

adb pull /data/misc/adb/adb_keys /adb_keys


For example:

adb pull /data/misc/adb/adb_keys c:/adb_keys


The above command will save the adb_keys file to the root of your C: drive. You can change the destination folder to your liking. 

Now the job of the authorised device is done. You can disconnect it and disable USB debugging.


Once you get a copy of adb_keys, reboot the phone with the broken screen into recovery.
Now connect the broken phone to the computer using USB.
We need to copy the adb_keys file to the broken device. Use the command below:

adb push  /data/misc/adb


For example:

adb push c:/adb_keys /data/misc/adb



After the file is copied, reboot your device using adb reboot et voila! You can now use adb shell on that computer. 


Furthermore, if you want to have full control over your device even with a broken screen, the tool from this thread lets you use your device through your Windows PC even if your touchscreen doesn't work or you can't see anything. (It requires Java Runtime Environment and Visual C++ redistributable). Or keep using Vysor. 

Disclaimer:

The above guide was not made by me and I did not test it myself, I just made minor changes. Just try it and let us know. Good luck. 

Original source : XDA Developers