BackButtonCallback

Functional Interface:

This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.
```
@FunctionalInterface
public interface BackButtonCallback
```
Callback for native back button presses while the Unblu UI is displayed.

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`boolean`	`handlePress(boolean hasBackStack)`	Called whenever the native back button is pressed while the Unblu UI is displayed.

- Method Detail
  - handlePress
```
boolean handlePress(boolean hasBackStack)
```
    Called whenever the native back button is pressed while the Unblu UI is displayed.
    
    Parameters:
    
    hasBackStack - is true if there is still some back stack in the webView, false otherwise
    
    Returns:
    
    true if the press of the button is handled by the callback, false if the SDK should handle it.