Lego

A powerful Android library for building complex RecyclerView. Building a list is as simple as playing Lego game.

List<Model> =>Lego=> List<View>. 像搭积木一样构建你的RecyclerView列表。

中文介绍

What Lego does

When you need to build a RecyclerView which contains different types of ViewHolder, you may always need to maintain a huge Adapter and calculate which type should be displayed on each position.

Now, forget those different types and viewTypeOfPosition() calculation in your terriable Adapter.

When using Lego, you just need to do:

1. Build a empty List<Object>;
2. Put all your data into this List<Object>;
3. Take this List<Object> to RecyclerView. 

It's done! RecyclerView will auto find the ViewHolder based on List and display.

How to use Lego

For example, we have three viewHolders to display in a RecyclerView: AppleViewHolder, OrangeViewHolder, BananaViewHolder. Their own data class are Apple, Orange, Banana.

You have two ways to build with Lego.

1. Use String Id to identify each ViewHolder

@LegoViewHolder(id = "apple_view_holder")
class AppleViewHolder implements ILegoViewHolder {
    @Override
    public View initView(ViewGroup parent) { ... }

    @Override
    public void bindData(Object data, int position, @Nullable Bundle argument) { ... }
}

@LegoViewHolder(id = "orange_view_holder")
class OrangeViewHolder implements ILegoViewHolder {
    @Override
    public View initView(ViewGroup parent) { ... }

    @Override
    public void bindData(Object data, int position, @Nullable Bundle argument) { ... }
}

@LegoViewHolder(id = "banana_view_holder")
class BananaViewHolder implements ILegoViewHolder {
    @Override
    public View initView(ViewGroup parent) { ... }

    @Override
    public void bindData(Object data, int position, @Nullable Bundle argument) { ... }
}

That's it! In your RecyclerView, you can do as below:

RecyclerView recyclerView = findViewById(R.id.recycler_view);

// 1. create a LegoRecyclerAdapter
LegoRecyclerAdapter adapter = new LegoRecyclerAdapter();

// 2. create a data list of Object
List<Object> data = new ArrayList<>();

// 3. add LegoItem into data
data.add(LegoItem.create("apple_view_holder"));
data.add(LegoItem.create("orange_view_holder"));
data.add(LegoItem.create("banana_view_holder"));

// 4. It's done
adapter.swapData(data);
recyclerView.setAdapter(adapter)

Run this code, the RecyclerView will show these three viewHolders, try it or run our sample!

2. Simpler Way: use Data object to identify each ViewHolder

@LegoViewHolder(bean = Apple.class)
class AppleViewHolder implements ILegoViewHolder {
    @Override
    public View initView(ViewGroup parent) { ... }

    @Override
    public void bindData(Object data, int position, @Nullable Bundle argument) { 
      Apple apple = (Apple) data;
      ...
    }
}

@LegoViewHolder(bean = Orange.class)
class OrangeViewHolder implements ILegoViewHolder {
    @Override
    public View initView(ViewGroup parent) { ... }

    @Override
    public void bindData(Object data, int position, @Nullable Bundle argument) { 
      Orange orange = (Orange) data;
      ...
    }
}

@LegoViewHolder(bean = Banana.class)
class BananaViewHolder implements ILegoViewHolder {
    @Override
    public View initView(ViewGroup parent) { ... }

    @Override
    public void bindData(Object data, int position, @Nullable Bundle argument) {   
      Banana orange = (Banana) data;
      ...
    }
}

In your RecyclerView, do as below:

RecyclerView recyclerView = findViewById(R.id.recycler_view);

// 1. create a LegoRecyclerAdapter
LegoRecyclerAdapter adapter = new LegoRecyclerAdapter();

// 2. create a data list of Object
List<Object> data = new ArrayList<>();

// 3. add LegoItem into data
data.add(new Apple());
data.add(new Orange());
data.add(new Banana());

// 4. It's done
adapter.swapData(data);
recyclerView.setAdapter(adapter)

Bingo! This will display same three ViewHolders as above, but this way is easier to use.

Get LegoViewHolder instance

adapter.setOnLegoViewHolderListener(new OnLegoViewHolderListener() {
    @Override
    public void onCreate(@NonNull ILegoViewHolder viewHolder) {
        if (viewHolder instanceof AppleViewHolder) {
            makeToast("Create AppleViewHolder");
        } else if (viewHolder instanceof OrangeViewHolder) {
            makeToast("Create OrangeViewHolder");
        }
    }
});

ViewHolder cache

If you know your page need at least 2 AppleViewHolder and 3 OrangeViewHolder, you can tell Lego to generate ViewHolder instance and inflate. When data(maybe from server) arrives, you can display immediately and no need to do the ViewHolder Inflate.

LegoCache legoCache =
    new LegoCache.Builder(recyclerView)
    .cache(OrangeViewHolder.class, 2)
    .cache(AppleViewHolder.class, 2)
    .build();
adapter.setLegoCache(legoCache);

Sample

Here is our sample code you can try.

Install

implementation 'com.wingjay.lego:library:0.9.2'
annotationProcessor 'com.wingjay.lego:lego-processor:0.9.2'

if you use Kotlin, use as below

implementation 'com.wingjay.lego:library:0.9.2'
kapt 'com.wingjay.lego:lego-processor:0.9.2'

Proguard

-keep @interface com.wingjay.lego.LegoBean
-keep @interface com.wingjay.lego.LegoViewHolder

-keep @com.wingjay.lego.LegoBean class *
-keepclassmembers class * {
    @com.wingjay.lego.LegoBean *;
}
-keep @com.wingjay.lego.LegoViewHolder class *
-keepclassmembers class * {
    @com.wingjay.lego.LegoViewHolder *;
}