Electronic device including hidden display and method for displaying information thereof

1. A method for displaying information in a foldable electronic device having a flexible primary display and a secondary display that is exposed when the foldable electronic device is folded, the method comprising:

calculating, by a processor, a folding angle of the flexible primary display;

calculating a size of an exposed area of the secondary display based on the folding angle, wherein the exposed area of the secondary display is configured to display content;

displaying a first content item on the exposed area of the secondary display based on the size of the exposed area of the secondary display; and

updating the secondary display in response to detecting a change in the size of the exposed area of the secondary display.

2. The method of claim 1 , further comprising detecting a movement of a cover of the secondary display.

3. The method of claim 1 , wherein:

the flexible primary display is disposed on a first surface of the foldable electronic device,

the secondary display is disposed on a second surface of the foldable electronic device, and

the size of the exposed area of the secondary display is inversely proportional to a magnitude of the folding angle of the flexible primary display.

4. The method of claim 1 , further comprising:

obtaining a quaternion data vector of a first region of the flexible primary display and a quaternion data vector of a second region of the flexible primary display; and

calculating an inner product of unit vectors associated with the first and second regions by using the quaternion data vectors,

wherein the folding angle of the flexible primary display is calculated based on the inner product.

5. The method of claim 1 , wherein the first content item is displayed on the secondary display in response to detecting that the size of the exposed area meets a threshold.

6. The method of claim 1 , wherein displaying the first content item on the secondary display includes displaying a portion of the first content item when the exposed area has a first size and displaying the entire first content item when the exposed area has a second size.

7. The method of claim 1 , wherein displaying the first content item on the secondary display includes displaying a text item when the exposed area has a first size and displaying an icon when the exposed area has a second size.

8. The method of claim 1 , wherein updating the secondary display includes:

displaying a second content item concurrently with the first content item when the size of the exposed area is increased; and

hiding at least some of the first content item from display when the size of the exposed area is decreased.

9. The method of claim 1 , wherein updating the secondary display includes replacing the first content item with a second content item.

10. The method of claim 1 , wherein a brightness of the secondary display is selected based on the size of the exposed area.

11. An electronic device comprising:

a foldable body;

a flexible primary display formed on one surface of the foldable body;

a secondary display formed on another surface of the foldable body;

a cover arranged to cover or expose the secondary display;

a memory; and

at least one processor operatively coupled to the memory, configured to:

calculate a folding angle of the flexible primary display;

calculate a size of an exposed area of the secondary display based on the folding angle, wherein the exposed area of the secondary display is configured to display content;

display a first content item on the exposed area of the secondary display based on the size of the exposed area of the secondary display; and

update the secondary display in response to detecting a change in the size of the exposed area of the secondary display.

12. The electronic device of claim 11 , wherein the at least one processor is further configured to detect a movement of a cover of the secondary display.

13. The electronic device of claim 11 , wherein the size of the exposed area of the secondary display is inversely proportional to a magnitude of the folding angle of the flexible primary display.

14. The electronic device of claim 11 , wherein the at least one processor is further configured to:

obtain a quaternion data vector of a first region of the flexible primary display and a quaternion data vector of a second region of the flexible primary display;

calculate an inner product of unit vectors associated with the first and second regions by using the quaternion data vectors; and

the folding angle of the flexible primary display is calculated based on the inner product.

15. The electronic device of claim 11 , wherein the first content item is displayed on the secondary display in response to detecting that the size of the exposed area meets a threshold.

16. The electronic device of claim 11 , wherein displaying the first content item on the secondary display includes displaying a portion of the first content item when the exposed area has a first size and displaying the entire first content item when the exposed area has a second size.

17. The electronic device of claim 11 , wherein displaying the first content item on the secondary display includes displaying a text item when the exposed area has a first size and displaying an icon when the exposed area has a second size.

18. The electronic device of claim 11 , wherein updating the secondary display includes:

displaying a second content item concurrently with the first content item when the size of the exposed area is increased; and

hiding at least some of the first content item from display when the size of the exposed area is decreased.

19. The electronic device of claim 11 , wherein updating the secondary display includes replacing the first content item with a second content item.

20. The electronic device of claim 11 , wherein a brightness of the secondary display is selected based on the size of the exposed area.

21. A non-transitory computer readable-medium storing one or more processor-executable instructions which when executed by at least one processor cause the at least one processor to perform a method comprising the steps of:

calculating a folding angle of a flexible primary display;

calculating a size of an exposed area of a secondary display based on the folding angle, wherein the exposed area of the secondary display is configured to display content;

displaying a first content item on the exposed area of the secondary display based on the size of the exposed area of the secondary display; and

updating the secondary display in response to detecting a change in the size of the exposed area of the secondary display.