To edit an Android XML file online, you need to have an account at POEditor (it's free and takes just a few seconds to register) and follow these steps.
Step 1: Add a new project in your Dashboard.
Step 2: Add a language to the localization project and then import your strings from your XML file, using the Import functionality in the project page. Choose in the import options to 'Also import translations to a language' and select the language you've just added.
This language will automatically be set as your project's Default Reference Language after you import the translations. You can change the DRL in Project Settings.
Step 3: Add more languages to the project and manage their translation, with the optional help of contributors.
Step 4: When you're done with the XML language edit, use the Export button in any translation page to download a localized XML file.
Creating a first project launches a Free Trial, which increases the account's limit from 1000 strings to 30 000. When the trial period is over, the free account can still be used up to 1000 strings.