Nexus 4 shows up empty on Windows Explorer I connected my Nexus 4 to my PC via USB.

When I open the device in Windows Explorer, though, it's empty.

I made sure to install an MTP driver.

How can I access the file system of my phone?

Edit: I have not unlocked my phone, because I'm unable to: the screen cracked, and is nonresponsive. Can I get around that?

Edit: So the Nexus 4 actually doesn't support OTG. Do I have another option? Take out the hard drive and put it in a new phone?
Here are 2 methods to access your phone

Method 1: Android Debug Bridge (ADB)
You will need:Your device, Access to a PC
This method has proved to be the most helpful for users in terms of their feedback after completion. However, this method will only work if you have USB debugging enabled on your Android phone. If you don’t have this option enabled, move on to the second method on the list.
The ADB is used to create a bridge between your PC and your Android device. This bridge can be used to unlock the device and to access your files.
Download the Android SDK package on your PC. You can download it here. Make sure that you download the correct version for your PC. Once downloaded, extract the zip file on your PC.
Download the relevant USB drivers for your phone. You can get the USB drivers for your device from your manufacturer’s website.
Launch the Command Prompt on your PC and change the directory to where the ADB file is located. Type in the following command in Command Prompt.
cd C:/android/platform-tools
Connect your Android phone to your PC using a micro USB cable and enter the following command. If your phone is recognized, you’ll see some numbers in the Command Prompt message.
adb device
Type in the following two commands. You’ll need to type in the second command immediately after the first one. Replace 1234 in the first command with your actual password.
adb shell input text 1234
shell input keyevent 66
If the process is successful, your phone should be unlocked. You can now backup your important files and contacts.

 

Method 2: USB On the Go Mouse Method
You will need: Your device An OTG adaptor, A USB mouse
If you can’t access USB debugging , you can try
the USB mouse method. This involves connecting your phone to a USB
mouse with an OTG adaptor. Here’s a full list of compatible devices
where you check to see if your device is covered. If not, users have
reported that a USB keyboard can be used to unlock a device locked
behind a passcode when a mouse hasn’t worked, so it’s worth giving the
cable a try.
You can find the adaptor cable online, and it’s reasonably
inexpensive. If it lets you access your device, than it’s definitely
worth the price.
Once connected, the mouse will drain your battery, and some devices,
(such as the Galaxy S3 Mini) will also be unable to charge during the
process, so make sure your battery is sufficiently charged beforehand.
Once you have the wire to hand, the process itself is reasonably easy
to complete.
Connect the micro USB side of the OTG cable in your Android tablet or
phone and plug in the USB mouse in the OTG adapter.
As soon as you connect the mouse, you should see a pointer on your
screen. You can now use the mouse to unlock the pattern or use it to
press the keys of the on-screen keyboard if you have a password lock.

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