Java
A library for supporting convex material shadows

MaterialShadows

A library for seamlessly integrating Material shadows. The library takes existing material shadows to next level by adding the following features :

• Convex shadows : The shadows are not only rectangular or circular, they can take any convex shape depending on the view and its content.
• Support for shadow offsets : The library allows developers to set X and Y offset for the shadows.
• Support for shadow intensity : The library also has support for setting shadow intensity via shadowAlpha attribute.
• Shadows for semi-transparent views : The library allows shadows for semi-transparent views.
• Support for Async Shadow calculations : The library allows the operations to be async to avoid blocking the UI thread for long calculations.
• Shadow animations : The library supports fade out animation for shadow.

Usage

Just add the following dependency in your app's build.gradle

dependencies {
      compile 'com.sdsmdg.harjot:materialshadows:1.1.0'
}

How does this work ?

The MaterialShadowViewWrapper is an extension of Relative Layout. All the child views go through the same process of generating shadow as given below :

1. First a bitmap is generated from the drawing cache of the view.
2. The bitmap is traversed pixel by pixel to remove all transparent pixels and get a list of points corresponding to the actual outline of the content of the view.
3. Since the points corresponding to outline may give a concave path, hence GrahamScan algorithm is used to generate a convex hull of the outline points.
4. A path is created from the points of the resulting convex hull.
5. This path is passed to a CustomViewOutlineProvider object that is later attached to the view itself.
6. Hence we get a convex shadow for any type of view based on its content.

P.S. : All the calculations related to graham scan are done asynchronously by default. This behavior can be controlled by calculateAsync parameter. (Thanks Yaroslav!)

Example Usage 1 (Simple)

XML

<com.sdsmdg.harjot.materialshadows.MaterialShadowViewWrapper
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <ImageView
            android:layout_width="130dp"
            android:layout_height="130dp"
            android:elevation="5dp"
            android:src="@drawable/poly" />

</com.sdsmdg.harjot.materialshadows.MaterialShadowViewWrapper>

Result

Example Usage 2 (Offset)

XML

<com.sdsmdg.harjot.materialshadows.MaterialShadowViewWrapper
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:shadowOffsetX="-15"
        app:shadowOffsetY="30">

        <ImageView
            android:layout_width="130dp"
            android:layout_height="130dp"
            android:elevation="10dp"
            android:src="@drawable/poly" />

</com.sdsmdg.harjot.materialshadows.MaterialShadowViewWrapper>

Result

Example Usage 3 (Shadow intensity)

XML

<com.sdsmdg.harjot.materialshadows.MaterialShadowViewWrapper
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:shadowOffsetX="-15"
        app:shadowOffsetY="30"
        app:shadowAlpha="0.9">

        <ImageView
            android:layout_width="130dp"
            android:layout_height="130dp"
            android:elevation="10dp"
            android:src="@drawable/poly" />

</com.sdsmdg.harjot.materialshadows.MaterialShadowViewWrapper>

Result

Example Usage 4 (Semi-transparent views)

XML

<com.sdsmdg.harjot.materialshadows.MaterialShadowViewWrapper
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:shadowOffsetX="-30"
        app:shadowOffsetY="30">

        <ImageView
            android:layout_width="130dp"
            android:layout_height="130dp"
            android:elevation="10dp"
            android:background="#55000000" />

</com.sdsmdg.harjot.materialshadows.MaterialShadowViewWrapper>

Result

Documentation

Limitations

1. Since the bitmap is traversed pixel by pixel, the performance for large views is bad. Hence the use of the library is limited to small views.
2. Currently the shadow is generated only for direct children of the MaterialShadowViewWrapper. Hence if the desired views are placed inside a Linear Layout or some other view group, then each view must be wrapped by a seperate MaterialShadowViewWrapper. This doesn't affect the performance as the number of operations are still the same, but affects the quality of code.
3. Each child of MaterialShadowViewWrapper is assigned same offset and shadow intensity. If fine control over every view's shadow is required then it must be wrapped inside its own MaterialShadowViewWrapper. Again this doesn't affect the performance, just the quality of code.

Credits

1. Yaroslav : Implementation of asynchronous calculations and shadow animations.

License

MaterialShadows is licensed under MIT license. View license.