me.zhanghai.android.fastscroll:library

AndroidFastScroll

Fast scroll for Android RecyclerView and more.

This is not an officially supported Google product.

Why AndroidFastScroll?

• Fully customizable: Override track, thumb, popup, animation and scrolling.
• Easy-to-use defaults: Predefined default style, Material Design 2 style and animation.
• Extensive view support: Out-of-box support for RecyclerView, ScrollView, NestedScrollView and WebView, plus any view with a ViewHelper implementation.
• Window insets friendly: Support setting a separate padding for scrollbar.
• Clean implementation: Decoupled touch handling, animation and scrolling logic.

Preview

Sample APK

Implementation

This library is loosely based on the following AOSP implementations:

• Framework ListView FastScroller.
• AndroidX RecyclerView FastScroller.
• Launcher3 RecyclerViewFastScroller.

Integration

Gradle:

implementation 'me.zhanghai.android.fastscroll:library:1.3.0'

This library uses Java 8 bytecode, so you will need to enable it in your project as well:

android {
    ...
    // For Java projects
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
    // For Kotlin projects
    kotlinOptions {
        jvmTarget = JavaVersion.VERSION_1_8.toString()
    }
}

Usage

Simply create a FastScroller with FastScrollerBuilder, and enjoy!

new FastScrollerBuilder(recyclerView).build();

You can also implement PopupTextProvider in your RecyclerView.Adapter to show a popup.

For more customization, please use the methods on FastScrollerBuilder. Namely:

• setViewHelper() allows providing a custom ViewHelper to support more views.
• setPopupTextProvider() allows providing a custom PopupTextProvider if your RecyclerView.Adapter cannot implement that interface.
• setPadding() allows setting a custom padding for the scrollbar, instead of the padding of the view.
• setTrackDrawable() and setThumbDrawable() allow setting custom drawables for the scrollbar. The android:state_pressed state will be updated for them so you can use a selector. The track drawable needs to have an intrinsic width and the thumb drawable needs to have an intrinsic size, in order to allow proper touch event handling.
• setPopupStyle() allows customizing the popup view with a lambda that will receive the view.
• setAnimationHelper() allows providing a custom AnimationHelper to use an alternative scrollbar animation.
• disableScrollbarAutoHide() allows disabling the auto hide animation for scrollbar. This implies using a DefaultAnimationHelper.
• useDefaultStyle() and useMd2Style() allow using the predefined styles, which sets the drawables and popup style. useDefaultStyle(), as its name suggests, is the default style when a FastScrollerBuilder is created.

The default ViewHelper implementation for RecyclerView supports both LinearLayoutManager and GridLayoutManager, but assumes that each item has the same height when calculating scroll, as there's no common way to deal with variable item height. If you know how to measure for scrolling in your specific case, you can provide your own ViewHelper implementation and fast scroll will work correctly again.

If you are using any RecyclerView.ItemDecoration that implements onDrawOver(), you might be interested in FixItemDecorationRecyclerView which can fix the drawing order.

If you are using any other library that makes use of RecyclerView.OnItemTouchListener (e.g. recyclerview-selection), you might be interested in FixOnItemTouchListenerRecyclerView which can correctly handle cancellations when dispatching touch events to listeners. You may also want to configure this library before others so that this library can take precedence in touch event handling.

You can also refer to the sample app source for how things like window insets and lift on scroll are implemented.

License

Copyright 2019 Google LLC

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.