Filter Drawer

Sample

The sample app is under app directory

Features

Plug-and-play - Adapt default implementations with your own filters and you are good to go
Independent - Set everything up without modifying your activity's layout file
Customizable - Extend base class implementations and take control of everything
Versatile - Create your own filters for literally anything
Built-in adapter - So you don't need to worry about the filtering logic for your recycler view

Usage

We will use the implementation in the sample project as examples.

0. Implement

To include FilterDrawer in your project, add the following dependency to your app's build.gradle:

implementation "com.camerash:filterdrawer:1.0.0"

1. Extend

Create classes that extends DefaultParnetItem and DefaultChildItem.

These are the classes used to control and configure items in the FilterDrawer.

Default Parent Item

ParentItem serves as the controller for the categories you see in the Filter Drawer.

The default behaviour has already been implemented for you in the class DefaultParentItem

You need to implement the following required abstract methods when extending the class:

// Required methods
override fun getParentIcon(): Int
override fun getParentTitle(): String
override fun getChildCollection(): List<ChildItem>
override fun allowSelectMultiple(): Boolean

// Optional modifiers
override fun getLayoutRes(): Int
override fun getRootLinearLayoutId(): Int
override fun getToggleExpandOnClickViewId(): Int
override fun getViewHolder(v: View): ViewHolder
override fun getDefaultTextColorRes(): Int
override fun getSelectedTextColorRes(): Int
override fun getDefaultIconColorRes(): Int
override fun getSelectedIconColorRes(): Int

The parent class in our pet sample app, namely PetFilterCategory, has the following implementation:

class PetFilterCategory(val type: FilterType, @DrawableRes val icon: Int, private val childList: List<PetFilter>): DefaultParentItem() {

    enum class FilterType { Kind, Size }

    override fun getParentIcon(): Int = this.icon

    override fun getParentTitle(): String = this.type.name

    override fun getChildCollection(): List<ChildItem> = this.childList

    override fun getSelectedTextColorRes(): Int = R.color.colorPrimary

    override fun allowSelectMultiple(): Boolean = true
}

In the above example, the type, icon and the category's child filters in childList are initialized in the class's constructor.

Note that the method getChildCollection() requires a List of ChildItem. Here we have also defined our own class that extends ChildItem , called PetFilter, which will be explained below.

Default Child Item

ChildItem serves as the controller for the filters you see under every categories in the Filter Drawer.

The default behaviour has already been implemented for you in the class DefaultChildItem

You need to implement the following required abstract methods when extending the class:

// Required methods
override fun getTitle(): String
override fun getSelectedColorRes(): Int

// Optional modifiers
override fun getLayoutRes(): Int
override fun getViewHolder(v: View): ViewHolder
override fun getDefaultTextColorRes(): Int
override fun getSelectedTextColorRes(): Int
override fun getDefaultBackgroundColorRes(): Int
override fun getSelectedBackgroundColorRes(): Int

The child class in our pet sample app, namely PetFilter, has the following implementation:

class PetFilter(val filter: Enum<*>) : DefaultChildItem() {

    enum class Kind { Cats, Dogs, Rabbits, Hamsters, Birds }
    
    enum class Size { Small, Medium, Large }

    override fun getTitle(): String = this.filter.name

    override fun getSelectedTextColorRes(): Int = R.color.colorPrimary
}

As we have two types of filters, Kind and Size, we defined the suitable enum classes and instantiatePetFilter with an Enum called filter, which serves as the filter's identification.

2. Build

After finishing the above parent and child classes, we can build the filter using DrawerBuilder.

DrawerBuilder requires two types to instantiate, which each extends ParentItem and ChildItem respectively.

For our example, we first construct our filter list:

 private fun constructFilterItems(): ArrayList<PetFilterCategory> {

     val pet = PetFilterCategory(PetFilterCategory.FilterType.Kind, R.drawable.round_pets_24, PetFilter.Kind.values().map { PetFilter(it) })

     val animal = PetFilterCategory(PetFilterCategory.FilterType.Size, R.drawable.round_size_24, PetFilter.Size.values().map { PetFilter(it) })

     return arrayListOf(pet, animal)
 }

Then construct our FilterDrawer in the onCreate method of your activity:

val filterDrawer = DrawerBuilder<PetFilterCategory, PetFilter>(this)
                    .displayToolbar(true)
                    .withItems(constructFilterItems())
                    .build()

This builds our FilterDrawer and automatically adds it to the activity.

Up to this point, you should be able to run your app and check out the FilterDrawer by swiping from the right of the screen.

3. Filter

Our filter is ready, but there are yet to have things to be filtered.

Let's create a class named Pet. To utilize the built-in FilterableRecyclerAdapter later on, we need to implement the DiffItemCallback<T> interface as follows:

class Pet(val name: String, val imageUrl: String, val kind: PetFilter.Kind, val size: PetFilter.Size) : DiffItemCallback<Pet> {
    override fun isIdentical(item: Pet): Boolean {
        return name == item.name
    }

    override fun hasSameRepresentation(item: Pet): Boolean {
        return imageUrl == item.imageUrl
    }
}

isIdentical provides information on whether the two items are identical at a data level. You should compare IDs or item-specific variables here.

hasSameRepresentation provides information on whether the two items looks the same when shown to users. You should compare resources shown to users here.

The built-in adapter compare items by using the platform-providedDiffUtil.Callback(), where our isIdentical interface is called in its areItemsTheSame method, and hasSameRepresentation is called in its areContentsTheSame method.

For more informations, check out the library's source code, or the official documentation on DiffUtil.

Next, let's create our adapter by extending the built-in FilterableRecyclerAdapter. The adapter looks more or less the same with a typical recycler adapter, with the exception of the method filter which you will need to implement.

In out example, the implementation of method filter would look like this:

override fun filter(data: Pet, parent: PetFilterCategory, child: PetFilter): Boolean {
    return child.filter == when (parent.type) {
        PetFilterCategory.FilterType.Kind -> data.kind
        PetFilterCategory.FilterType.Size -> data.size
    }
}

filter will get called whenever the filters in FilterDrawer is updated. In the code above, it returns whether the given Pet matches the given PetFilter under certain PetFilterCategory.

All nested checkings are done under the hood, so all we need to worry about is whether the given Pet matches the single given PetFilter.

Finally, setup the your RecyclerView with our adapter, and pass a reference of our FilterDrawer to the adapter by:

adapter.bindFilterDrawer(filterDrawer)

and you are all set!

Customization

Please refer to the KDoc here to familiarize yourself with the base implementations.

Follow the default implementation to extend ParentItem and ChildItem would also be a good start for your customization.

API

Please refer to the KDoc here

Library used

Materialize by Mike Penz
ExpandableLayout by Daniel Cachapa

Developed By

Contribution

Feel free to open issues if there are any suggestions or bugs.

Contribution by opening pull requests are also welcomed!