Recyclerview is one of the powerful widgets inside android framework. But creating adapters with multiple view types is always exhausting. Not anymore. MultiViewAdapter makes it easy for you to create adapter with multiple view types easily. Using the library you will be able to build composable view holders, which can be re-used across your app. Apart from this, MultiViewAdapter adds many other useful features into the library as add-ons.

1. Why this library
2. Feature Showcase
3. Gradle Dependency
4. Core Concepts
5. Basic Usage
6. Learn More
7. Changelog
8. Contribution
9. Credits
10. License

Have you ever displayed multiple view types inside a single adapter? Have you ever added selection mode to an adapter? Have you ever set different span size to different items inside a single adapter? Have you ever added swipe-to-dismiss / drag & drop / infinite scrolling features to your adapter?

If the answer was yes, then you must know how hard it is to do any one of these. What if you had to all of these inside a single adapter. Phew.

1. In default adapter approach, code is not re-usable as it is.
2. If you have to add multiple viewtypes the code grows painfully.
3. If the data needs to be updated, its hard to write the updation logic and call the correct notify method.

To solve the above problems, you can also use a different library. But all such libraries have a common restrictions - Your data model will be polluted with the view logic.

1. Your data objects should be extended/implement from library's model, which can interfere with your object modeling.
2. View holder creation and binding has to be written inside the data model. You are forced to keep layout and view references inside the model class itself.
3. For complex lists, generic notifyDataSetChanged method will be called during updation. Also these libraries don’t take advantage of DiffUtil.
4. You have to write switch cases, if you want to have different item-decorations/span-size/selection-modes/expansion for different view types.
5. You lose the type information when accessing objects ie., you need to cast the object every time you need it.

MultiViewAdapter solves all of these requirements. The library was specifically designed in a way to not interfere with your object modeling and hierarchy.

Here are the few features which are possible with this library.

Multiple Viewtypes	Multiple Spans	Other Features

Selection	Item Expansion	Section Expansion

The Gradle dependency is available via JCenter. JCenter is the default maven repository used by Android Studio. The minimum API level supported by this library is API 14.

dependencies {
    implementation 'dev.ahamed.mva2:adapter:2.0.0-alpha01'
}

dependencies {
    implementation 'dev.ahamed.mva2:ext-data-binding:2.0.0-alpha01' // DataBinding
    implementation 'dev.ahamed.mva2:ext-decorators:2.0.0-alpha01'   // Decorators
    implementation 'dev.ahamed.mva2:ext-rxdiffutil:2.0.0-alpha01'   // RxDiffUtil
}

Just add '-SNAPSHOT' to the version name

dependencies {
    implementation 'dev.ahamed.mva2:adapter:2.0.0-SNAPSHOT' // Library
}

To use the above snapshot version add the following to your project's gradle file

allprojects {
    repositories {
        maven {
            url 'https://oss.jfrog.org/artifactory/oss-snapshot-local'
        }
    }
}

Core mantra of MultiViewAdapter - Separation of view logic from data management logic. You get two different components which are :

1. Section - Component to hold your data. All data related updates will run here and proper notify method will be called on the adapter.
2. ItemBinder - Component which creates and binds your view holder. All view related logic should go here.

Section is the building block for MultiViewAdapter. Section will hold your data which needs to be displayed inside the recyclerview - data can be a single item or list of items. When the underlying data is changed the section will calculate the diff and call the correct notify method inside the adapter. You can add as many as Section to an adapter.

There are different types of sections.

ItemBinder is the class where all view related code should be written. ItemBinder is responsible for creating and binding view holders. The method signatures are kept close to the default RecyclerView.Adapter method signatures. For each viewtype inside the recyclerview, you need to create an ItemBinder.

ItemBinder allows you to have different decoration for different view types. Apart from this, by using an ItemBinder you will be able to add Swipe-to-dismiss, drag and drop features.

Lets create an adapter which displays a list of cars. Follow these steps.

1. You need to create an ItemBinder for your model. ItemBinder is responsible for creating and binding your view holders. Following is the code snippet of ItemBinder for CarModel class.

CarBinder

public class CarBinder extends ItemBinder<CarModel, CarBinder.CarViewHolder> {

  @Override public CarViewHolder createViewHolder(ViewGroup parent) {
      return new CarViewHolder(inflate(R.layout.item_car, parent));
  }

  @Override public boolean canBindData(Object item) {
      return item instanceof CarModel;
  }

  @Override public void bindViewHolder(CarViewHolder holder, CarModel item) {
      holder.tvCarName.setText(item.getName());
  }

  static class CarViewHolder extends ItemViewHolder<CarModel> {
    
    TextView tvCarName;

    public CarViewHolder(View itemView) {
        super(itemView);
        tvCarName = findViewById(R.id.tv_car_name);
    }
  }
}

2. Now create an adapter and use the ItemBinder created above. Since we are displaying a list of items we need to create an ListSection object and add the data items to it. Add the section to adapter. Done.

In your Activity/Fragment

class CarListActivity extends Activity {
  private RecyclerView recyclerView;
  private List<CarModel> cars;

  public void initViews() {

      // Create Adapter
      MultiViewAdapter adapter = new MultiViewAdapter();
      recyclerView.setAdapter(adapter);

      // Register Binder
      adapter.registerBinders(new CarItemBinder());

      // Create Section and add items
      ListSection<YourModel> listSection = new ListSection<>();
      listSection.addAll(cars);

      // Add Section to the adapter
      adapter.addSection(listSection);
  }
}

Yay!! We are done.

1. Documentation Website - If you would like to learn more about various other features, kindly read the documentation. All features are documented with sample code which should help you set-up complex recyclerview adapters.
2. Sample App - Sample app showcases all the features of the adapter. Also it is an excellent reference for creating most complex usecases
3. JavaDocs

See the project's Releases page for a list of versions with their changelog. View Releases
If you watch this repository, GitHub will send you an email every time there is an update.

We welcome any contribution to the library. This project has a good infrastructure which should make you comfortable to push any changes. CI builds the project nightly and on every pull request, so you will know whether the build has breaking changes. CI also reports the code coverage difference on each pull request.

You can contribute to any of the following modules:

1. Core Library
2. Library Extensions
3. Sample App
4. Documentation
5. Design assets

This project stands on the shoulders of open source community. It is a must to credit where it is due.

1. AOSP - Android Open Source Project
2. Artifactory OSS - Repository manager to host snapshot builds
3. Bintray - Distribution platform
4. Bitrise - CI & CD service
5. Codecov - Code coverage hosting service
6. Docsify - Documentation generator
7. Github - Version control & project maanagement platform

Also this library uses following open source gradle plugins

1. Bintray Release - Plugin to release the library artifacts to bintray
2. Artifactory Publish - Plugin to release snapshots to artifactory oss

If this library does not suit your needs create an issue/feature request. Meanwhile check these awesome alternatives as well.

1. MultipleViewTypesAdapter - Original inspiration for this library
2. AdapterDelegates
3. Groupie
4. Epoxy

Copyright 2017 Riyaz Ahamed

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.