This will help display the Power Slider on the iPhone screen. After that, slide and turn off your phone and wait 30 seconds before pressing the power button to turn on the device.
Try resetting your iPhone
Resetting your iPhone to default settings works for a variety of issues, including camera issues. This should be your next logical step.
Go to settings.
Head to General, then click Reset.
Click Reset All Settings.
Try using the camera again and see if the issue is resolved. If it doesn’t, keep reading.
Turn off Voice Over
It sounds surprising that the black screen issue occurs when Voice-Over is enabled. You can simply fix this issue by following a few steps. Go to Phone Settings > General > Accessibility and turn off Voiceover.
After that, wait a bit and launch the camera app again.
Use Dr.Fone – System Repair to fix any iOS related issues.
If you don’t want to lose your important data files while repairing the black iPhone camera, take the help of Dr.Fone – System Repair.