A type based RecyclerView Adapter

Scope

Having screens with lists in Android is a very common use case and the need to write a RecyclerView adapter for each of the screens generates a lot of boilerplate code. When we talk about lists with multiple item types, this boilerplate code is even more significant, especially, when the same item appears in multiple lists and each of the adapters has to handle the given item. A quick solution would be to provide base adapters and extend those with only the specific items, however, this is ok in the short run, but it may cause extra overhead in the long run. Here, this library comes into the picture.

The library itself tries to reduce the amount of boilerplate code by leveraging the handling of an item type to item factories and the role of the adapter will be only to find the correct factory which can handle the given item. This way, the adapter becomes independent from the displayed items and can be reused in multiple places with different factories setup.

Setup

Latest version:

Ensure you have the HalcyonMobile GitHub Packages as a repository

// top level build.gradle
//..
allprojects {
    repositories {
        // ...
        maven {
            url "https://maven.pkg.github.com/halcyonmobile/recycler-typed-adapter"
            credentials {
                username = project.findProperty("GITHUB_USERNAME") ?: System.getenv("GITHUB_USERNAME")
                password = project.findProperty("GITHUB_TOKEN") ?: System.getenv("GITHUB_TOKEN")
            }
            // https://docs.github.com/en/github/authenticating-to-github/keeping-your-account-and-data-secure/creating-a-personal-access-token
        }
    }
}
// top level build.gradle.kts
//..
allprojects {
    repositories {
        // ...
        maven {
            url = uri("https://maven.pkg.github.com/halcyonmobile/recycler-typed-adapter")
            credentials {
                username = extra.properties["GITHUB_USERNAME"] as String? ?: System.getenv("GITHUB_USERNAME")
                password = extra.properties["GITHUB_TOKEN"] as String? ?: System.getenv("GITHUB_TOKEN")
            }
            // https://docs.github.com/en/github/authenticating-to-github/keeping-your-account-and-data-secure/creating-a-personal-access-token
        }
    }
}

Note: you only need one maven declaration with "halcyonmobile/{specific}", every other package will be accessible.

Add the library dependency

Add the following dependency to your build.gradle file.

implementation "com.halcyonmobile.recycler-extension:typed-adapter:<latest-version>"

Structure

The library comes with 3 RecyclerView.Adapter with some base implementations, which can be used when there are only simple scenarios, without any custom solution.

TypedRecyclerViewAdapter: The base class, represents the backbone of the application, where the whole delegation logic happens.

PagingTypedRecyclerViewAdapter The logic is inherited from the base class, but extends with handling of paginated lists with a loading more indicator.

RecyclerAdapter & PaginationRecyclerAdapter Simple implementations of the previous two abstract classes.

Usage

You can use any of the adapter implementations based on the requirements for the given list. If the default loading indicator from PaginationRecyclerAdapter is not suitable for your case, then you can override it and provide your custom loading indicator. By default, it uses a circular loading indicator with the primary color.

In order to create and support an item type in a list, you have to follow 4 simple steps:

• Create a data class which holds your domain model and implement the RecyclerItem interface.
• Create an item factory (extend the TypedAdapterBaseFactory or ClickableTypedAdapterFactory base classes) (choose the second if your item needs to be clickable).
• Submit your factory to your adapter instance.
• Map your domain model to the newly created UiModel class and submit that list to the adapter.
• Continue this until you provided a factory for each of the item types which can be present in your list.

Note that the order of your submitted factories should take into consideration the occurance of the item. This is important, because the underlying implementation searches through the list until it find a factory which can bound the item and if you set as the last factory the factory which can handle the most elements (ex. list and header), then you will perform a lot of unnecessary operations under the hood.

If any other, specific use case needs to be supported by your list, then you will need to extend one of the adapters and implement the code for your use case.

License

Copyright 2020 HalcyonMobile

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

   https://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.