androidmaterial-designandroid-coordinatorlayoutandroid-appbarlayoutandroid-nestedscrollview
Android CollapsingToolbar/ AppBarLayout scroll behind status bar behaviour top padding
I'd like to use CoordinatoryLayout, AppBarLayout and CollapsingToolbarLayout to create a layout that resembles the below example from Google Calendar.
The key things I'm trying to replicate:
- Scrolling the content behind the status bar
- Rounded corners at the top of the scroll container
- Enough room at the top of the screen for the header to not look squashed
The Question Google Calendar appears to be growing the scroll container as the user scrolls. How would I go about doing this or something similar to achieve the look I'm after?
I've put together a quick example of what I'm trying to build:
activity_scrolling.xml
<androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:animateLayoutChanges="true"
tools:context="uk.co.exampleapplication.ScrollingActivity">
<com.google.android.material.appbar.AppBarLayout
android:id="@+id/app_bar_layout"
android:layout_width="match_parent"
android:layout_height="wrap_content">
<com.google.android.material.appbar.CollapsingToolbarLayout
android:id="@+id/collapsing_toolbar"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_scrollFlags="scroll|exitUntilCollapsed">
<include
android:id="@+id/lay_header"
layout="@layout/layout_header" />
</com.google.android.material.appbar.CollapsingToolbarLayout>
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@drawable/scroll_header_background"
android:elevation="16dp"
android:paddingBottom="12dp">
<TextView
android:id="@+id/sectionTitleText"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="16dp"
android:layout_marginTop="32dp"
android:text="Title"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<Button
android:id="@+id/filter_button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="22dp"
android:layout_marginEnd="16dp"
android:text="Button"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
</com.google.android.material.appbar.AppBarLayout>
<androidx.core.widget.NestedScrollView
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
tools:context=".ScrollingActivity"
tools:showIn="@layout/activity_scrolling">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_margin="@dimen/text_margin"
android:text="@string/large_text" />
</androidx.core.widget.NestedScrollView>
</androidx.coordinatorlayout.widget.CoordinatorLayout>
layout_header.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/header"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
android:paddingHorizontal="16dp"
android:paddingTop="60dp"
android:paddingBottom="40dp"
app:layout_collapseMode="parallax"
tools:ignore="HardcodedText">
<TextView
android:id="@+id/title"
android:layout_width="match_parent"
android:layout_height="24dp"
android:layout_marginTop="8dp"
android:layout_marginEnd="16dp"
android:text="Title"
android:textColor="#FFF"
android:textSize="20sp"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/subtitle"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Subtitle"
android:textColor="#FFF"
android:textSize="16sp"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/title" />
</androidx.constraintlayout.widget.ConstraintLayout>
scroll_header_background.xml
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">
<corners
android:bottomLeftRadius="0dp"
android:bottomRightRadius="0dp"
android:topLeftRadius="20dp"
android:topRightRadius="20dp" />
<solid android:color="#FFFFFF" />
<size
android:width="64dp"
android:height="64dp" />
</shape>
My attempt is included below. The header scrolls behind the toolbar as desired but I'd like some additional top padding above my views (about the height of the top inset/ status bar would be sufficient). Google Calendar appears to be solving this by having the container grow as the user scrolls.
Solution
Implement an AppBarLayout.OnOffsetChangedListener that will adjust top padding on the ConstraintLayout that holds the TextView and the Button. (Call this view "viewToGrow".) You can also do other things in the listener like change the corner radius of the drawable as the appbar scrolls.
The following example adjusts top padding to give the header more room. This padding is increased as the appbar scrolls up and decreases as it scrolls down. The demo app also removes the corner radius of the drawable during the final 15% of the appbar scroll.
ScrollingActivity
class ScrollingActivity : AppCompatActivity() {
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_scrolling)
val viewToGrow: View = findViewById(R.id.viewToGrow)
val baseTopPadding = viewToGrow.paddingTop
// Determine how much top padding has to grow while the app bar scrolls.
var maxDeltaPadding = 0
val contentView = findViewById<View>(android.R.id.content)
ViewCompat.setOnApplyWindowInsetsListener(contentView) { _, insets ->
maxDeltaPadding = insets.systemWindowInsetTop
insets
}
// Get key metrics for corner radius shrikage.
var backgroundRadii: FloatArray? = null
var maxRadius: FloatArray? = null
val backgroundDrawable = (viewToGrow.background as GradientDrawable?)
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N && backgroundDrawable != null) {
backgroundRadii = backgroundDrawable.cornerRadii
maxRadius = floatArrayOf(backgroundRadii!![0], backgroundRadii[1])
}
// Set up the app bar and the offset change listener.
val appBar: AppBarLayout = findViewById(R.id.app_bar_layout)
val appBarTotalScrollRange: Float by lazy {
appBar.totalScrollRange.toFloat()
}
appBar.addOnOffsetChangedListener(AppBarLayout.OnOffsetChangedListener { _, verticalOffset ->
// Add/remove padding gradually as the appbar scrolls.
val percentOfScrollRange = (-verticalOffset / appBarTotalScrollRange)
val deltaPadding = maxDeltaPadding * percentOfScrollRange
val newTopPadding = baseTopPadding + deltaPadding.toInt()
if (newTopPadding != viewToGrow.paddingTop) {
viewToGrow.setPadding(
viewToGrow.paddingLeft,
newTopPadding,
viewToGrow.paddingRight,
viewToGrow.paddingBottom
)
// Change the drawable radius as the appbar scrolls.
if (backgroundRadii != null && maxRadius != null) {
val radiusShrinkage = if (percentOfScrollRange > (1.0f - CORNER_SHRINK_RANGE)) {
(1.0f - percentOfScrollRange) / CORNER_SHRINK_RANGE
} else {
1.0f
}
backgroundRadii[0] = maxRadius[0] * radiusShrinkage
backgroundRadii[1] = maxRadius[1] * radiusShrinkage
backgroundRadii[2] = maxRadius[0] * radiusShrinkage
backgroundRadii[3] = maxRadius[1] * radiusShrinkage
backgroundDrawable!!.cornerRadii = backgroundRadii
}
}
})
}
companion object {
const val CORNER_SHRINK_RANGE = 0.15f
}
}
