- Known problems
On devices with Android 5 and newer, writing to memory card is still problem due to Android's policy to make this unnecessarily complicated. Instead of plain writing to memory card, as it is possible for Internal memory, app must ask user for special permission in a very obscure way.
Unfortunately, all file managers have to do this, except of those lucky ones which are shipped in some devices by manufacturer, those apps have special rights and don't need to use special tricks to provide such essential functionality.
So here is what needs to be done in order to gain write access to external memory card on Android 5 and newer. Luckily this is one-time action only, afterwards writing to same card should be without problems. However note that moving across folders on memory card will be slow, as due to this system X-plore needs to copy/delete file instead of plain renaming (this applies to Android 5/6, as on Android 7 real moving is possible).
When there is writing attempt to memory card (copy, delete, rename) X-plore shows introduction dialog as in the image shown on this page. It shows all steps that need to be done in following Android system dialog, so that X-plore gains write access to memory card.
So let's walk through this if the helping dialog is too brief.
First, a system app is opened, which look like kind of file manager. This app is built in Android. Expanding menu from left side reveals all available storage locations, such as Internal memory, memory cards, and possibly USB devices.
To make things harder, Android may not initially show memory card, so we may need to click menu at top right, and choose Show SD card from there. Then we can find the SD card in left menu, and click on it to select it. The helping picture on right shows it as “SD card”, although on some Android devices it shows the label of memory card, so it may be different for each user. You have to be clever and click your real memory card.
Afterwards, this “kind of file manager” lists contents of the memory card. We're not interested what's listed, just about Select button shown at bottom. (On some Android versions it adds label of memory card, on other Androids it's plain “Select”.)
When clicking the Select button at bottom, Android finally gives X-plore permissions to write to memory card, and saves this information somewhere in system settings. X-plore then will be able to write to same memory card without further dialogs.
When you change memory card, you'll get this procedure again, as permission is valid only for particular memory card.
On Android 7 and newer, the permission asking dialog is greatly simplified, and X-plore shows just this dialog when asking writing permission: