First, read the English article below.

If you didn't back up your iPhone to iTunes, you won't be able to restore your iPhone's text messages. You may be able to use a third-party service to restore your texts, though you'll need to pay in order to do so and the chances of your texts being recovered are slim. iTunes is white with a multicolored musical note on it.  If you're prompted to click Download iTunes, do so before continuing. You'll need to update and then restart your computer before you can continue. If you want to use an iCloud backup instead, open your iPhone's Settings. Do so by attaching your iPhone charger cable to the computer and then plugging it into your phone. If you're using an iCloud backup, scroll down and tap General, then scroll all the way down and tap Reset. It's an iPhone-shaped icon in the top-left side of the iTunes window. Doing this opens the "Summary" page. For an iCloud backup, tap Erase All Content and Settings, then enter your passcode if prompted. It's on the right side of the "Backups" section near the top of the page.  If prompted, turn off "Find My iPhone" before proceeding. If your iPhone doesn't automatically back up, you can click Back Up Now to save a current backup just in case you wish to restore to it later. If you're using an iCloud backup, tap Erase iPhone twice, then wait for your phone to complete the erasing procedure. A drop-down menu will appear. For an iCloud backup, press the Home button when prompted. This must be a date at which your deleted text messages were still on the iPhone.  For an iCloud backup, select a language and region, select a Wi-Fi network, and then tap Restore from iCloud Backup. If your phone's last backup still isn't from a date on which your text messages were on your iPhone, you cannot restore your iPhone's texts. It's on the right side of the "Backups" area of the page. Doing so will prompt your iPhone to begin restoring the backup, text messages included.  If your selected backup is password-protected, first enter the password. You'll need to update your iPhone's... 

Now, please write a short abstract for it in Chinese. Abstract:
只有之前创建过备份，才能使用这种方法来恢复短信。 在电脑上打开iTunes。 将iPhone连接到电脑。 点击“设备”图标。 点按恢复备份。 出现提示时，点击“iPhone名称”旁边的方框。 点击一个备份日期。 点击“备份”部分右边的恢复。 等待数据恢复完毕。