Basic Usage

Eli Hart edited this page Jan 5, 2018 · 13 revisions

There are two main components of Epoxy:

  1. The EpoxyModels that describe how your views should be displayed in the RecyclerView.
  2. The EpoxyController where the models are used to describe what items to show and with what data.

Creating Models

Epoxy generates models for you based on your view or layout. Generated model classes are suffixed with an underscore (_) are are used directly in your EpoxyController classes.

From Custom Views

Add the @ModelView annotation on a view class. Then, add a "prop" annotation on each setter method to mark it as a property for the model.

@ModelView(autoLayout = Size.MATCH_WIDTH_WRAP_HEIGHT)
public class HeaderView extends LinearLayout {

  ... // Initialization omitted

  @TextProp
  public void setTitle(CharSequence text) {
    titleView.setText(text);
  }
}

A HeaderViewModel_ is then generated in the same package.

More Details

From DataBinding

If you use Android DataBinding you can simply set up your xml layouts like normal:

<layout xmlns:android="http://schemas.android.com/apk/res/android">
    <data>
        <variable name="title" type="String" />
    </data>

    <TextView
        android:layout_width="120dp"
        android:layout_height="40dp"
        android:text="@{title}" />
</layout>

Then, create a package-info.java file in any package and add an EpoxyDataBindingLayouts annotation to declare your databinding layouts.

@EpoxyDataBindingLayouts({R.layout.header_view, ... // other layouts })
package com.airbnb.epoxy.sample;

import com.airbnb.epoxy.EpoxyDataBindingLayouts;
import com.airbnb.epoxy.R;

From this layout name Epoxy generates a HeaderViewBindingModel_.

More Details

From ViewHolders

If you use xml layouts without databinding you can create a model class to do the binding.

@EpoxyModelClass(layout = R.layout.header_view)
public abstract class HeaderModel extends EpoxyModelWithHolder<Holder> {
  @EpoxyAttribute String title;

  @Override
  public void bind(Holder holder) {
    holder.header.setText(title);
  }

  static class Holder extends BaseEpoxyHolder {
    @BindView(R.id.text) TextView header;
  }
}

A HeaderModel_ class is generated that subclasses HeaderModel and implements the model details.

More Details

Using your models in a controller

A controller defines what items should be shown in the RecyclerView, by adding the corresponding models in the desired order.

The controller's buildModels method declares which items to show. You are responsible for calling requestModelBuild whenever your data changes, which triggers buildModels to run again. Epoxy tracks changes in the models and automatically binds and updates views.

As an example, our PhotoController shows a header, a list of photos, and a loader (if more photos are being loaded). The controller's setData(photos, loadingMore) method is called whenever photos are loaded, which triggers a call to buildModels so models representing the state of the new data can be built.

public class PhotoController extends Typed2EpoxyController<List<Photo>, Boolean> {
    @AutoModel HeaderModel_ headerModel;
    @AutoModel LoaderModel_ loaderModel;

    @Override
    protected void buildModels(List<Photo> photos, Boolean loadingMore) {
      headerModel
          .title("My Photos")
          .description("My album description!")
          .addTo(this);

      for (Photo photo : photos) {
        new PhotoModel()
           .id(photo.id())
           .url(photo.url())
           .addTo(this);
      }

      loaderModel
          .addIf(loadingMore, this);
    }
  }

Or with Kotlin

An extension function is generated for each model so we can write this:

class PhotoController : Typed2EpoxyController<List<Photo>, Boolean>() {

    override fun buildModels(photos: List<Photo>, loadingMore: Boolean) {
        header {
            id("header")
            title("My Photos")
            description("My album description!")
        }

        photos.forEach {
            photoView {
                id(it.id())
                url(it.url())
            }
        }

        if (loadingMore) loaderView { id("loader") }
    }
}

Integrating with RecyclerView

Get the backing adapter off the EpoxyController to set up your RecyclerView:

MyController controller = new MyController();
recyclerView.setAdapter(controller.getAdapter());

// Request a model build whenever your data changes
controller.requestModelBuild();

// Or if you are using a TypedEpoxyController
controller.setData(myData);

If you are using the EpoxyRecyclerView integration is easier.

epoxyRecyclerView.setControllerAndBuildModels(new MyController());

// Request a model build on the recyclerview when data changes
epoxyRecyclerView.requestModelBuild();

Kotlin

Or use Kotlin Extensions to simplify further and remove the need for a controller class.

epoxyRecyclerView.withModels {
        header {
            id("header")
            title("My Photos")
            description("My album description!")
        }

        photos.forEach {
            photoView {
                id(it.id())
                url(it.url())
            }
        }

        if (loadingMore) loaderView { id("loader") }
    }
}

More Reading

And that's it! The controller's declarative style makes it very easy to visualize what the RecyclerView will look like, even when many different view types or items are used. Epoxy handles everything else. If a view only partially changes, such as the description, only that new value is set on the view, so the system is very efficient

Epoxy handles much more than these basics, and is highly configurable. See the wiki for in depth documentation.

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