Q: The battery of my iPad four drawn very fast after update to iOS 8.1 and the sensitivity of my iPad decrease until I cannot swipe it and is very lag >< please fix it immediately

Hello alicelan,

After reviewing your post, I have located an article that can help with device errors. You may want to consider restoring your device to factory settings to resolve the issues you've described:

Use iTunes to restore your iOS device to factory settings

Restoring iOS software deletes all your data and content from your device, including songs, videos, contacts, photos, and calendar info.

Before you restore your device

1. Make sure you’re using the latest version of iTunes.
2. Use iTunes to back up your device. Transfer and sync any additional content to your computer.
3. Turn off Find My iPhone in Settings > iCloud on your device to disable Activation Lock.

Restore your iOS device

1. Connect your iOS device to your computer using the cable that came with it.
2. Select your iPhone, iPad, or iPod touch when it appears in iTunes. In the Summary panel, click Restore.

   

3. Click Restore again to confirm that you want to restore your device to factory settings and delete all data and content. iTunes will download the iOS software file and restore your iOS device.

   

4. After your iOS device is restored to factory settings, it will restart. Once it does, you’ll see the "Slide to set up” welcome screen. Follow the steps in the iOS Setup Assistant. You can set up your device as new or using a previous backup. If your iOS device has cellular service, it will activate after you restore.

   

Learn more

• If you get an error message, find out how to fix most update and restore errors.
• If your iOS device with cellular service doesn’t activate after restoring, find out how to fix activation issues.
• If your iOS device restarts repeatedly or isn’t responding, for example if you see a stopped progress bar or no progress bar, put the device into recovery mode and restore it again.

Thank you for contributing to Apple Support Communities.

Cheers,

BobbyD