Since the introduction of LED flash to smartphones, there have been hundreds of flashlight apps flooding Google Play, since most Android phones do not have built-in flashlight apps, including the HTC One.
Third-party flashlights are great for lighting up dark corners, but sometimes we don't have the time, or patience, to unlock our phones and open an app. Or worse yet, we could download a malicious app, bringing with it all sorts of malware onto our devices.
XPosed Torch, created by Mohamed Karami (better known as the renowned wanam), lets you quickly turn on your LED light using the Volume Up button on your One, all with an open-source mod that's free of malware. This is an Xposed module so be sure that your One is rooted and that you have Xposed Framework installed.
Open Xposed Installer on your HTC One and tap the Downloads section, then find the module named Xposed Torch and tap the Download button.
Allow the module to install and then tap Done once it has finished. Now go to the Module section of Xposed and make sure to check the box next to Xposed Torch to activate the module. Then reboot your device.
The settings page for Xposed Torch is pretty bare bones, but it does come with some useful options. You should enable the Torch Helper so that you can still use the Volume Up trigger even if your device is in deep sleep mode.
Also, you can enable the flashlight to work even when you have music playing, so be careful when holding the Volume Up button—we don't want you going deaf. This is where you may want to adjust the Long-press delay, although I found the default setting perfect for my use. The option to Use Home button as a trigger does not work for the One, but a fix is supposed to be in the works.
And that's it folks! There are always going to be alternative flashlight apps, but with Xposed Torch you know you'll have the quickest option.