Add some depth to your Android scrolling using the parallax effect!

Step 1. Add the JitPack repository to your build file

allprojects {
  repositories {
    ...
    maven { url 'https://jitpack.io' }
  }
}

Step 2. Add the dependency

dependencies {
  implementation 'com.github.prolificinteractive:parallaxpager:${parallaxpagerVersion}'
}

There are 4 important steps:

1. Use a ParallaxContainer in layout XML

2. Create a layout XML file for each page

3. Wrap the Activity Context

4. Add the attachment code to onCreate of your Activity or onCreateView of your Fragment

Use the class com.prolificinteractive.parallaxpager.ParallaxContainer in your layout XML, sizing it however you like.

Ex:

<com.prolificinteractive.parallaxpager.ParallaxContainer
      android:id="@+id/parallax_container_1"
      android:layout_width="match_parent"
      android:layout_height="match_parent"/>

Each page must have its own layout XML file. Use whichever Layouts or Views you like, as usual.

Ensure this line is added to the Root Element:

xmlns:app="http://schemas.android.com/apk/res-auto"

Assign any combination of the following attributes (all floats):

• x_in: as the View enters the screen, it will translate in the horizontal direction along with user swiping, at a rate multiplied by this value. Default is 0.

• x_out: as the View leaves the screen, it will translate in the horizontal direction along with user swiping, at a rate multiplied by this value. Default is 0.

• y_in: as the View enters the screen, it will translate downward as the user swipes right to left, at a rate multiplied by this value. Default is 0.

• y_out: as the View leaves the screen, it will translate upward as the user swipes right to left, at a rate multiplied by this value. Default is 0.

• a_in: as the View enters the screen, it will fade in as the user swipes right to left, at a rate multiplied by this value. Default is 0.

• a_out: as the View leaves the screen, it will fade out as the user swipes right to left, at a rate multiplied by this value. Default is 0.

Ex:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

  <TextView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      app:x_in="@dimen/parallax_speed_medium"
      app:x_out="@dimen/parallax_speed_fast"
      app:y_in="@dimen/parallax_speed_medium_rev"
      app:y_out="@dimen/parallax_speed_fast"
      app:a_in="@dimen/parallax_speed_very_fast"
      app:a_out="@dimen/parallax_speed_very_fast"
      android:text="@string/text_1"
      />

  <TextView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      app:x_in="@dimen/parallax_speed_medium_rev"
      app:x_out="@dimen/parallax_speed_fast"
      app:y_in="@dimen/parallax_speed_medium"
      app:y_out="@dimen/parallax_speed_fast_rev"
      app:a_in="@dimen/parallax_speed_very_fast"
      app:a_out="@dimen/parallax_speed_very_fast"
      android:text="@string/text_2"
      />
</LinearLayout>

Keep in mind that negative values mean a change in direction for translation effects, and have no effect for alpha. For translation effects, values between 0 and 1 will result in a high level of funkiness.

Wrap the activity context using com.prolificinteractive.parallaxpager.ParallaxContextWrapper in your activity.

Ex:

  @Override
  protected void attachBaseContext(Context newBase) {
    super.attachBaseContext(new ParallaxContextWrapper(newBase));
  }

Note: If you are using this in conjunction with another library that wraps Context, it doesn't appear to like chaining them together. Instead, we've added the ability to hook into the View creation process to use with other libraries. The sample project shows how to hook into Calligraphy.

Ex:

  @Override
  protected void attachBaseContext(Context newBase) {
    super.attachBaseContext(
        new ParallaxContextWrapper(newBase, new OnViewCreatedListener() {
          @Override public View onViewCreated(View view, Context context, AttributeSet attrs) {
            //Setup view as needed
            return view; //Return the view passed in
          }
        })
    );
  }

Important steps in onCreate of an Activity (or onCreateView of a Fragment):

• Find the parallax container by ID

• Specify whether the pager should loop (true means it will loop)

• Submit a Layout Inflater and list the layouts for each page (in order). Currently there must be at least 2 in this list (repeats allowed).

Ex:

// find the parallax container
ParallaxContainer parallaxContainer = (ParallaxContainer) findViewById(R.id.parallax_container);

// specify whether pager will loop
parallaxContainer.setLooping(true);

// wrap the inflater and inflate children with custom attributes
parallaxContainer.setupChildren(getLayoutInflater(),
    R.layout.parallax_view_1,
    R.layout.parallax_view_2,
    R.layout.parallax_view_3,
    R.layout.parallax_view_4);

You can set a ViewPager.OnPageChangeListener after the attachment code in step 4.

// optionally set a ViewPager.OnPageChangeListener
parallaxContainer.setOnPageChangeListener(this);

You have access to the ViewPager by calling:

parallaxContainer.getViewPager();

This is exposed for use with existing code which requires a ViewPager instance. Please make sure that if you call methods like setAdapter or setOnPageChangeListener on the instance returned, that you do so with forethought and good reason.

Parallax views will be VISIBLE when onscreen, and GONE when offscreen. If you need to override this behavior, set this attribute on your View in XML:

app:override_visibility="true"

To report a bug or enhancement request, feel free to file an issue under the respective heading. If you wish to contribute to the project, fork this repo and submit a pull request.

Code contributions should follow the standards specified in the Prolific Android Code Style.

Copyright (c) 2018 Prolific Interactive

Parallax Pager is maintained and sponsored by Prolific Interactive. It may be redistributed under the terms specified in the LICENSE file.