What is an effective way to determine how much free space is on the SD card?
If you just want to check it yourself, here are the steps to do it:
I just found that there is a better SO answer to this question:
Here are some methods to get available space, these methods give you more control and you can get available space in different units bytes, kb, mb, gb.
Usable since API level 9:
Here is a function that allows you to retrieve the amount of memory in the android device.
You can very easily find out the amount of memory that is left of you SD card via the phones device information. Please elaborate if your requirements are something else.
Create a file and write one byte at a time until you get an out of space exception.