User interface method, system, and device in multitasking environment

A display apparatus in a multitasking environment, the display apparatus comprising:

• a screen;
• a hardware processor implementing a controller configured to:
• in response to receiving a first user input for displaying a first application, control the screen to display the first application on a full display area of the screen;
• in response to receiving a second user input or an input for displaying a second application, control the screen to display the second application on the screen, wherein the displayed second application visually overlaps the displayed first application;
• in response to receiving a third user input for the second application while the displayed second application is visually overlapping the displayed first application, adjust a size of the displayed first application and control the screen to display the first application, of which the size is adjusted, on a remaining display area excluding a partial display area of the screen while the second application is displayed on the partial display area;
• in response to receiving a fourth user input for displaying a third application while the first application is displayed on the remaining display area and the second application is displayed on the partial display area, identify a priority of the third application and a priority of the displayed first application;
• and
• in response to the priority of the third application being identified to be higher than the priority of the displayed first application, control the screen to display the third application on the remaining display area while the second application is displayed on the partial display area and to terminate the display of the first application.

A non-transitory computer-readable storage medium storing instructions configured to cause a processor to:

• in response to receiving a first user input for displaying a first application, display the first application on a full display area of a screen;
• in response to receiving a second user input or an input for displaying a second application, display the second application on the screen, wherein the displayed second application visually overlaps the displayed first application;
• in response to receiving a third user input for the second application while the displayed second application is visually overlapping the displayed first application, adjust a size of the displayed first application and displaying the first application, of which the size is adjusted, on a remaining display area excluding a partial display area of the screen while the second application is displayed on the partial display area;
• in response to receiving a fourth user input for displaying a third application while the first application is displayed on the remaining display area and the second application is displayed on the partial display area, identify a priority of the third application and a priority of the displayed first application;
• and
• in response to the priority of the third application being identified to be higher than the priority of the displayed first application, display the third application on the remaining display area while the second application is displayed on the partial display area and terminate the display of the first application.