Tired of looking for your things in the dark? With iOS 14 or later on iPhone 8 or later, you can quickly turn your lens on and off with two or three taps on the back of your iPhone using a feature called Back Tap. See how you can make the necessary adjustments.

How does Back Tap work?
Back Tap is an accessibility feature iOS which detects taps on the back of your iPhone using your phone's built-in accelerometer. Works on iPhone 8 and newer iPhones. When configured in Settings, you can use two or three taps to start many different ones ενέργειες on phone including shortcuts, which we will use here to turn on the flashlight.
Create a lens switch shortcut
To enable and disable the lens, we need to create a custom shortcut using the built-in Shortcuts application. To do this, open "Shortcuts". If you can not find it, try a Spotlight search: Swipe down the middle with one finger home screen your. Type "Shortcuts" in the search bar, then click the "Shortcuts" icon.

If you see the “Shortcuts” overview screen when the app opens, tap the “My Shortcuts” tab, then select “All Shortcuts”.

On the "All Shortcuts" screen, press the plus ("+") button.

Then you will see a "New Shortcut" page where you add them steps (called "actions") in the shortcut. First, let's rename the shortcut. Press the "ellipses" button (three dots).

Click on "Shortcut Name" and rename the shortcut to "Flashlight Toggle", then press "Done".

When you return to the shortcut screen, click "Add Action".

When the "Actions" box appears, look for "flashlight". Click "Set Flashlight" on Results.

The "Set Flashlight" action will appear in the action list. By default, it is set to activates the lens only when the shortcut is running. What we want it to do is turn the lens on or off when the shortcut is running. To do this, press the word "Turn" on the phrase "Turn flashlight on".

When the "Operation" menu appears, select "Toggle".

Back to the list actions, the "Flashlight" action should now read "Toggle flashlight". This means that if you run the shortcut and the lens is off, the lens will light up. If you perform the shortcut while the flashlight is on, the flashlight will go out.
Click "Done" to complete the shortcut.

After that, you will see the "Flashlight Toggle" shortcut in your list. You can try it now by pressing it button of the shortcut. If the lens lights up, press the shortcut button again to turn it off.

You are now ready to proceed to the next step: connecting the shortcut to Back Tap.
Configure the Back Tap to perform the lens shortcut
Now that we have set the shortcut that turns the lens on and off, we need to configure how activation with the Back Tap. To do this, open "Settings".

In Settings, go to Accessibility> Touch.

In the "Touch Settings" section, select "Back Tap".

In the "Back Tap" settings, select whether you want to activate your lens using two taps ("Double Tap") or three taps ("Triple Tap") on the back phone and then select the matching option.

Then scroll down the list of actions until you see the "Shortcuts" section. Select the "Flashlight Toggle" shortcut we just created.

Press once to make sure the change is registered, then exit Settings. The next time you double or triple press on the back part of your iPhone (depending on how it is set up), the iPhone lens will light up. Press the back two or three times again to turn it off. Are you ready!
Source of information: howtogeek.com