转换ArrayList <SomeClass> 到ArrayList <SomeInterface>

Question

I have 3 classes representing 3 differents things: Article , Photos , and Videos

All 3 things have 2 properties in common: A title and and image .

I have an interface called ImageTitleListItem that the 3 classes implement. That interface is just a getter/setter for title and image

I have 3 classes that are ArrayList :

Articles extends ArrayList<Article>
Photos extends ArrayList<Photo>
Videos extends ArrayList<Video>

I have an ArrayListAdapter that display a list of those images with there title .

The constructor of the ArrayListAdapter receive ArrayList<ImageTitleListItem> as a parameter

When I call it :

adapter = new ArrayListAdapter(Articles)

I have an error:

The constructor ArrayListAdapter(Articles) is undefined

That's normal, so i tried to cast it:

adapter = new ArrayListAdapter((ArrayList<ImageTitleListItem>)Articles)

Now the error is:

Cannot cast from Articles to ArrayList<ImageTitleListItem>

I'm relativly new to java so there's a trick I'm missing, can somebody help me on this.

Thanks

Answer 1

需要将ArrayListAdapter构造函数定义为

 ArrayListAdapter(List<? extends ImageTitleListItem> list)