The Parallax Pager

Add some depth to your Android scrolling.

Download

Use Gradle to grab the dependency from Maven Central:

compile 'com.prolificinteractive:parallaxpager:2.2.1'

Usage

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

1. Use a ParallaxContainer in layout XML

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"/>

2. Create a layout XML file for each page

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.

3. Wrap the Activity Context

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
          }
        })
    );
  }

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

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);

Extras

Extra 1. Setting a ViewPager.OnPageChangeListener

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

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

Extra 2. ViewPager access

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.

Extra 3. Overriding parallax visibility

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"

License

Copyright 2015 Prolific Interactive

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.