An Android layout class that supports animating the expansion and collapse of its child views.

I built this because all of the available libraries I tested were missing features or behaving unexpectedly in certain cases (e.g. rotation handling).

This library offloads as much work as possible to the parent layout to ensure that the rendering and size calculations behave as expected. This means that even complex features such as LinearLayout's weight tag are properly supported.

Currently the only implemented expandable layout is based on the framework's LinearLayout since it supports all of the requirements for my current use cases. If the need for other variants arises, it should be easy to adapt the current solution to a FrameLayout, RelativeLayout or others.

ExpandableLinearLayout supports animating:

• Views with a fixed height:

• Views with fill height (usually using weight > 0):

• Multiple views simultaneously:

• "Accordion" expansion (using two expandable layouts)

• RecyclerView items

Add the following lines to your root build.gradle:

allprojects {
    repositories {
        [...]
        maven { url "https://jitpack.io" }
    }
}

Then reference the library from your module's build.gradle:

dependencies {
    [...]
    compile 'com.github.cachapa:expandablelayout:1.2'
}

Add the ExpandableLinearLayout as the root of the layout you want to make expandable, and mark the relevant child views as expandable using the layout_expandable tag:

<net.cachapa.expandablelayout.ExpandableLinearLayout
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:el_duration="1000"
    app:el_expanded="true">

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Click here to toggle expansion" />

    <TextView
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:text="Fixed height"
        app:layout_expandable="true" />

</net.cachapa.expandablelayout.ExpandableLinearLayout>

Also supported are el_duration and el_expanded tags, for specifying the duration of the animation and whether the layout should start expanded, respectively.

To trigger the animation, simply grab a reference to the ExpandableLinearLayout from your Java code and and call either of expand(), collapse() or toggle().

A full demo of the library is included with the project under the demo directory.

Copyright 2016 Daniel Cachapa.

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.

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