The Weird and The Wonderful

The Weird and The Wonderful forum is a place to post Coding Horrors, Worst Practices, and the occasional flash of brilliance.

We all come across code that simply boggles the mind. Lazy kludges, embarrassing mistakes, horrid workarounds and developers just not quite getting it. And then somedays we come across - or write - the truly sublime.

Post your Best, your worst, and your most interesting. But please - no programming questions . This forum is purely for amusement and discussions on code snippets. All actual programming questions will be removed.

Re: #define Macros and the Preprocessor Used by the Resource Compiler

Dr.Walt Fair, PE13-Mar-19 6:27

Dr.Walt Fair, PE

13-Mar-19 6:27

I think that this is programming, so I{ll read something else in the Lounge.

CQ de W5ALT

Walt Fair, Jr., P. E.
Comport Computing
Specializing in Technical Engineering Software

Extending Generics with nested types

raddevus4-Mar-19 10:30

raddevus

4-Mar-19 10:30

The new way to make a ListView in Android apps is to use the RecyclerView.
It's quite a complex thing, just to create a ListView.

You will have to create an Adapter class based off your Model type (in my case and the example below that Model type is called Entry -- think JournalEntry).

The Adapter you create will contain a list of your Model :

Java

List<Entry> allEntries;

But, here is where it starts getting weird:

Your EntryAdapter has to extend A RecyclerView.Adapter of EntryAdapter.Viewholder :
So your class definition will look like the following:

Java

public class EntryAdapter extends RecyclerView.Adapter<EntryAdapter.ViewHolder>

It Gets Weirder
And it gets weirder (to me).

That Generic type (RecyclerView.Adapter) expects that your EntryAdapter contains a class named ViewHolder and EntryAdapter.ViewHolder extends RecyclerView.ViewHolder.

So here is just the basic outline of your EntryAdapter:

Java

public class EntryAdapter extends RecyclerView.Adapter<EntryAdapter.ViewHolder>{
    public List<Entry> allEntries;
    
    public EntryAdapter() {

    }
    public EntryAdapter(List<Entry> entryList) {
        allEntries = entryList;
    }

    public class ViewHolder extends RecyclerView.ViewHolder {

    }
}

My Head Explodes
For me, my head kind of explodes on all of that.

The entire reason you need to do all of that is because you need to override a method and implement a couple of methods from the Generic RecyclerView.Adapter.

So really, your basic class will look like the following

Java

public class EntryAdapter extends RecyclerView.Adapter<EntryAdapter.ViewHolder>{
    public List<Entry> allEntries;
    
    public EntryAdapter() {

    }

    public EntryAdapter(List<Entry> entryList) {
        allEntries = entryList;
    }

    public EntryAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    }

    @Override
    public void onBindViewHolder(EntryAdapter.ViewHolder holder, int position) {
    }

    public int getItemCount() {
    }

    public class ViewHolder extends RecyclerView.ViewHolder {

    }
}

A Few of Things That Stand Out
1. This really is the new expected way to simply create listview type of items in the Android dev world. The ListView type is being deprecated.
2. Generic / template type syntax is always difficult to read.
Here's my natural language reading of my EntryAdapter type:
I have an EntryAdapter that is a RecyclerView adapter of EntryAdapter viewholder. WTF | :WTF:

3. This kind of thing makes it kind of difficult to talk about the types and the code and ends up causing me just to memorize all of this. Maybe that is good but it's quite an extensive pattern just to get to a listview of items.

My brain hurts. But I did get it working at least.

Re: Extending Generics with nested types

Nathan Minier5-Mar-19 2:17

Nathan Minier

5-Mar-19 2:17

That's not too bad as far as infrastructure support goes. If you want a real nightmare, have a look at the Zend Framework someday. It will test your sanity.

I haven't written Java in years, but can you not define a generic version of the Adapter?

Java

public class ModelAdapter<T> extends RecyclerView.Adapter<ModelAdapter<T>.ViewHolder>{
   public List<T> allItems;
   ...
}

Or are the needs of that overriden method too specific?

"Never attribute to malice that which can be explained by stupidity."
- Hanlon's Razor

Re: Extending Generics with nested types

raddevus5-Mar-19 2:33

raddevus

5-Mar-19 2:33

Nathan Minier wrote:
but can you not define a generic version of the Adapter?

I'm not sure. But since I'm digging through this myself what would that do for me?
Are you thinking of creating a generic one that handles multiple types, maybe?

I think the only reason this is genericized is because it is an attempt to provide a generic way to bind model elements to the view and since those end up being specific fields then you have to (at this point) give it a specific implementation that you want to bind.

Anyways, I think that is the point.
Thanks for chiming in on the discussion. Thumbs Up | :thumbsup:

Re: Extending Generics with nested types

Dr.Walt Fair, PE13-Mar-19 6:28

Dr.Walt Fair, PE

13-Mar-19 6:28

That almost sounds like a programming discussion in the Lounge.

CQ de W5ALT

Walt Fair, Jr., P. E.
Comport Computing
Specializing in Technical Engineering Software

Re: Extending Generics with nested types

raddevus13-Mar-19 7:30

raddevus

13-Mar-19 7:30

Walt Fair, Jr. wrote:
That almost sounds like a programming discussion in the Lounge.

Is this sentence stating your shock?
A programming discussion in the lounge!!! What!?! Laugh | :laugh:

Re: Extending Generics with nested types

Dr.Walt Fair, PE7-May-19 5:50

Dr.Walt Fair, PE

7-May-19 5:50

Yeah, but I could be wrong. After all, I'm an engineer who never studied programming in school.

CQ de W5ALT

Walt Fair, Jr., P. E.
Comport Computing
Specializing in Technical Engineering Software

Documentation boggle of the day

Gary Wheeler6-Feb-19 8:22

Gary Wheeler

6-Feb-19 8:22

From the TCP/IP interface specification for some hardware I have to talk to:

A command is always sent from the CT to the WS and a response is always sent from the WS to the CT. The term command and response no longer dictate the order that the messages are sent, that is, the WS may send a response first and the CT will respond by sending a command.

And people wonder why I don't have any hair left...

Software Zen: delete this;