Touchscreen Problems

• The likely cause of an inability to use the slide unlock feature of your iPhone is a malfunctioning touchscreen. Other symptoms of touchscreen problems can include slow response of the touchscreen to your commands as well as unresponsive sections of your touchscreen other than the section displaying the slide unlock feature.
  
  

Testing the Screen

• Apple recommends that you test your iPhone's touchscreen functionality by opening the calculator app found on your iPhone. This application displays buttons running across the entire iPhone touchscreen except for the top row. Press each button on the calculator display to find the exact areas on the screen where the iPhone is unresponsive to your touch. You can test the top row of your iPhone by rotating the device, which brings up the scientific calculator found in the calculator app. Contact Apple Support if areas of your touchscreen are totally unresponsive.
  
  

Reboot

• To fix a stuck iPhone unlock slider, Apple recommends that you should turn off your device and reboot it. To do this, hold down the Sleep/Wake button found on top of your iPhone for a few moments until the red slider appears. Press and hold the Sleep/Wake button again until the Apple logo appears, indicating that your iPhone is turning on. Try to lock and unlock your iPhone again. Another troubleshooting method for the iPhone's slide unlock is to press down on the touchscreen with your entire hand; this sometimes wakes up the touchscreen enough to register your use of the slider.
  
  

Digitizer Problems

• The touch-screen display on an iPhone includes a component known as a digitizer that converts the touch of your fingers into data read by the iPhone's software. If the touch screen is unresponsive and the LCD display isn't cracked or broken, a malfunctioning digitizer is the likely problem. The digitizer is attached to the touch-screen panel in such a way that the component cannot be replaced by itself. Contact Apple's Service and Repair division through Apple Support to have your touch screen repaired.
  
  

Avoid Touchscreen Damage

• You can keep your touch screen working properly and avoid damage by remembering proper usage procedures for the touch screen whenever operating your iPhone. Do not operate the iPhone's touchscreen with wet hands, as the water can seep into the iPhone and cause hardware problems. Don't use gloves or protective plastic iPhone touch screen covers; skin contact is best to operate your iPhone's touch screen. If your touch screen gets dirty, clean it by wiping lightly with a slightly damp, lint-free cloth.