I have the same problem on iPhone 3G, 3GS and iPhone 4.
It cannot be the temperature difference as slide to unlock works all the time even when I have just removed it form my pocket.
Further more the sensor on the screen works via capacitive sensor not temperature sensor: http://electronics.howstuffworks.com/iphone2.htm
Some how when iPhone is ringing the slide to answer sometimes refuse to work!!
It happens on unknown contacts as well as known contacts.
This is my first post to any Apple forum. I've owned five iPhone 3 devices (kept getting replacements for various hardware problems) and finally switched to an iPhone 4 (or "mini iPad 4" since the "Phone" moniker isn't very appropriate for a device that is not able to make or receive phone calls very often) after "upgrading" my iPhone 3 to iOS 4 (which practically "bricked" my 3).
I'm terribly disappointed with Apple's iPhone design - not because I'm an Apple basher, but because I always believed that they had such a great brand. Their poor design is unworthy of such an iconic company.
I've experienced this "cannot slide to answer phone calls" software BUG (let's use the correct word) on several occasions. I'm not sure whether it is more frustrating to actually see the important call that I'm about to miss, or never see the call come in in the first place (the default iPhone/ATT behavior).
I've noticed a similar bug when the phone is locked but the iPod controls are on the screen, yet they are completely unresponsive to touch. I have to unlock the phone, then go to the iPod app to play music. Like the "cannot slide to answer phone call" bug, this one happens intermittently.
I've noticed that a posters who report Apple bugs often get a lot of negative responses from the many Apple apologists to the tune of "hey dude, if Apple's so bad, why don't you just get another phone/computer/etc ?" . . . this is the Apple-head equivalent of the old redneck "My country, love it or leave it!" response to antiwar protesters in the 60's.
I've also read other responses to posters who complain (or merely question) certain iPhone "features" (i.e. poor user interfaces) to the effect of "RTFM!" Again, this is unworthy of any product that would aspire to the ranks of "great design". In fact, the very definition of elegant design is that one should not have to "FR" the "FM".
A third category of "helpful" bug post responses is the "workaround" (although it's often not called that, because that would imply that there was some sort of bug that needed to be worked around). The procedural lengths that Apple-heads will go to to avoid confronting the awful truth that the iOS is buggy and the user interface is cute, but woefully inadequate, is fairly amusing.
A fourth interesting category of responses to bug postings (like this thread) is from Apple apologists who invent new physics to explain certain phenomena (i.e. bugs), as evidenced in the "thermal touch screen" theories espoused on this thread.
This is an Apple-sponsored forum. Are there no lurking Apple representatives who can comment about these bugs? Many of these bugs have been around since the first iPhone. Even Microsoft responds to bug reports. What's up Apple? Have you no shame???
This is not an App problem. It may be an IOS problem. I just had my iPhone 4 replaced. My old iPhone 4 never did this. But the replacement phone did this immediately out of the box, I didn't even get a chance to leave the mall where the Apple store was and the slider wasn't working, there were no additional Apps on the phone yet. Also, the symtoms got worse when I updated the phone to IOS Version 4.3(8F190).
I have this issue as well. It's very sporadic and I can't figure out what makes the phone prone to the problem, though I don't think it's associated with being in my pocket. In fact, I can't recall it ever happening when it is in my pocket... only when I'm in the office and phone is laying on my desk.
I have the same problem on my iPhone 4. The problem started after two months of usage and it was mostly when my wife was calling (insert joke here) then it "spred" to my daughter. I restored my iPhone but the problem continued so I called ATT and Apple. I sent the phone back to Apple. they tested it and they said nothing was wrong with the phone. They did a software reinstal and sent it back. I restored from iTunes and the problem returned within one day. Today the slider froze when the alarm went off at 6:30am. VERY frustrating.
I'm experiencing the same problem. It only happens once in a while. The "Slide to Answer" is totally unresponsive. One time, i pushed the "home" button and it allowed me to "slide to answer" It happens when its in my pocket, it happens when its sitting on my table, but only once in a while. iPhone 4 4.3.1
If so many people on the internet have encountered this problem, i cant believe apple hasn't acknolwedged it. Anyone find a fix, or cause for this yet?
I have had this happen every so often with both my iPhone 3 and 4. I always understood that the touch screen was reacting to a change in capacitance where it was being touched, not heat or pressure. For the change to be detected, there must be some difference with your finger. (You'll notice that the screen doesn't react to the touch of a ballpoint pen or work if you're wearing gloves (unless they're damp)). If your hands are really dry, you may not be generating a sufficient difference to be detected.
When this happens to me, I moisten my finger and swipe again (yes, I keep my hands clean). Works every time.
Keep some moisturizer handy.
This is not because people's hands are dry.
This is NOT a user issue.
IT DOES NOT MATTER WHAT YOU DO - whether your hands are moist or dry, whether it is cold or warm, whether the phone is in your pocket or not. YOu can try to swipe the **** thing 20 times, it will not work.
Once you hit to power button on the top (and miss your call) the screen becomes responsive again...
THIS IS A BUG and that is a fact - and it's one that is happening to a lot of people. I've worked in the tech sector for 20 years,
My feeling is that this is either a bug present in the firmware or something in a fairly common app that is causing this....
I had a 3G for a year, then a 3GS for 2 years...Never had this issue...but since the first day I got my brand new iphone4 5 weeks ago it has been an issue on and off.
iPhone 4 on Verizon, 2 months old, never dropped, fewer than 20 apps. Call comes in from contact or non-contact slider will not slide. Clean fingers, no gloves. AFTER call is missed and press top button a few times, I can work the slide with the same finger and call person back and tell them the iPhone is messed up and not to buy one.
This happens 1 to 3 times per day, about 1 call in 5-10.
Friend said shutting phone off for an hour would "reset" things and resolve the problem. Cutting off for 10 minutes or overnight does not resolve the problem which recurrs during the same day as powering off.
Hardly seems like hardware problem given quick return of function with no obvious change of physical conditions. Time to broadcast issue more widely.
Talked Apple into giving me a new iPhone 4. The problem REAPPEARED after I restored from backup. The Apple rep said the cause is most likely a currupt software issue. He wanted me to restore as new and NOT SYNC ANYTHING. I chose to not do that. Going to wait and see how annoying the problem becomes before I wipe the phone completly. I took the precaution of syncing my contacts to gmail so I have a clean set of contacts if I have to do a "bare metal" restore at some future point.
The same problem with my iphone4 too. I tried every thing in order to get rid of this problem. But no use, then i tried to find the couse why its not working while receving incoming calls! The 1st reason is, the phone heats while reciving incoming call and it equals with the tepmrature of finger so it could not slide up. But you can use another finger to slide it. Some times it helps. Next reason is dust and face sweat which dries over the phone! And it can interupt to get sence of finger heat, if you clean it up hardly you can slide it to answer.
But best way to get read of this Is to install "tap to unlock themes" from cydia. And i suggest to the apple guys to add this tap to answer option to the next updates!