A simple solution for implementing backdrop for Android

Backdrop

This library makes it easy to implement a Backdrop pattern with a CoordinatorLayout

Download

JCenter (Recommended):

For support library:

dependencies {
    implementation 'ru.semper-viventem.backdrop:backdrop:0.1.5'
}

For Android X:

dependencies {
    implementation 'ru.semper-viventem.backdrop:backdrop:0.1.5_x'
}

JitPack:

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

dependencies {
    implementation 'com.github.Semper-Viventem:BackdropView:0.1.5'
}

How to use it?

You need to add a layout Toolbar, back container and foreground container

Add BackdropBehavior to the Foreground View Container:

XML

<android.support.design.widget.CoordinatorLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <android.support.v7.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

    <LinearLayout
        android:id="@+id/backContainer"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">
        
        <!-- anything -->
    </LinearLayout>

    <!-- Add BackdropBehavior to this view -->
    <android.support.design.card.MaterialCardView
        android:id="@+id/foregroundContainer"
        app:layout_behavior="ru.semper_viventem.backdrop.BackdropBehavior"
        android:layout_width="match_parent"
        android:layout_height="match_parent">
        
        <!-- anything -->
    </android.support.design.card.MaterialCardView>

</android.support.design.widget.CoordinatorLayout>

Kotlin

I used this extension to search for behavior:

fun <T : CoordinatorLayout.Behavior<*>> View.findBehavior(): T = layoutParams.run {
    if (this !is CoordinatorLayout.LayoutParams) throw IllegalArgumentException("View's layout params should be CoordinatorLayout.LayoutParams")

    (layoutParams as CoordinatorLayout.LayoutParams).behavior as? T
            ?: throw IllegalArgumentException("Layout's behavior is not current behavior")
}

...

val backdropBehavior: BackdropBehavior = foregroundContainer.findBehavior() // find behavior

with(backdropBehavior) {
        attachBackContainer(R.id.backContainer) // set back container
        attachToolbar(R.id.toolbar) // set toolbar
        
        // set navigation icons for toolbar
        setClosedIcon(R.drawable.ic_menu)
        setOpenedIcon(R.drawable.ic_close)
        
        // add listener
        addOnDropListener(object : BackdropBehavior.OnDropListener {
            override fun onDrop(dropState: BackdropBehavior.DropState, fromUser: Boolean) {
                // TODO: handle listener            
            }
        })
}

...

GitHub