Question

I have this java code:

tgia = new ThumbsGalleryAdapter(this, profilePositionsOverlay.items);

and I get this error:

The constructor ThumbsGalleryAdapter(SharePositionMapActivity, List) is undefined
SharePositionMapActivity.java
/com.shopzeus.android.majorforms.activity.MainActivity/src/com/shopzeus/android/majorforms/activity
line 114 Java Problem

Constructor of ThumbsGalleryAdapter is:

public ThumbsGalleryAdapter(Activity aActivity, List<ThumbsGalleryItem> aItems)

Type of profilePositionsOverlay.items:

List<SharedPositionMapItem>

The name ThumbsGalleryItem refers to an interface:

public interface ThumbsGalleryItem {
    public String getTitle();
    public String getRemotePath();
}

Finally, SharedPositionMapItem is a class that implements ThumbsGalleryItem:

private static class SharedPositionMapItem extends OverlayItem implements ThumbsGalleryItem

The question is, of course: why List<SharedPositionMapItem> is not type compatible with List<ThumbsGalleryItem>? Because SharedPositionMapItem implements ThumbsGalleryItem, I would expect them to be compatible. What is the solution?

Answer 1

public ThumbsGalleryAdapter(Activity aActivity, List<? extends ThumbsGalleryItem> aItems)

For more details see:
http://codeidol.com/java/javagenerics/Subtyping-and-Wildcards/The-Get-and-Put-Principle/
and this
Explanation of the get-put principle