Find a background to animate when launching a dialog or activity

This CL makes the launch animations a bit more robust by trying to find
a background in the View that is expanded into the activity/dialog
instead of just taking the View background (that can sometimes be null).

See b/222668708#comment1 and #comment2 for before/after videos.

Bug: 222668708
Test: Manual
Change-Id: I590b6d77a7c9b29a73f37e1f8072643cc8c0bcfa

1 files changed, 40 insertions, 10 deletions

diff --git a/packages/SystemUI/animation/src/com/android/systemui/animation/GhostedViewLaunchAnimatorController.kt b/packages/SystemUI/animation/src/com/android/systemui/animation/GhostedViewLaunchAnimatorController.kt
index 183584227087..3f7e0f0fb527 100644
--- a/packages/SystemUI/animation/src/com/android/systemui/animation/GhostedViewLaunchAnimatorController.kt
+++ b/packages/SystemUI/animation/src/com/android/systemui/animation/GhostedViewLaunchAnimatorController.kt
@@ -33,6 +33,7 @@ import android.view.ViewGroup
 import android.view.ViewGroupOverlay
 import android.widget.FrameLayout
 import com.android.internal.jank.InteractionJankMonitor
+import java.util.LinkedList
 import kotlin.math.min
 
 private const val TAG = "GhostedViewLaunchAnimatorController"
@@ -81,21 +82,51 @@ open class GhostedViewLaunchAnimatorController(
      * [backgroundView].
      */
     private var backgroundDrawable: WrappedDrawable? = null
-    private val backgroundInsets by lazy { getBackground()?.opticalInsets ?: Insets.NONE }
+    private val backgroundInsets by lazy { background?.opticalInsets ?: Insets.NONE }
     private var startBackgroundAlpha: Int = 0xFF
 
     private val ghostedViewLocation = IntArray(2)
     private val ghostedViewState = LaunchAnimator.State()
 
     /**
-     * Return the background of the [ghostedView]. This background will be used to draw the
-     * background of the background view that is expanding up to the final animation position. This
-     * is called at the start of the animation.
+     * The background of the [ghostedView]. This background will be used to draw the background of
+     * the background view that is expanding up to the final animation position.
      *
      * Note that during the animation, the alpha value value of this background will be set to 0,
      * then set back to its initial value at the end of the animation.
      */
-    protected open fun getBackground(): Drawable? = ghostedView.background
+    private val background: Drawable?
+
+    init {
+        /** Find the first view with a background in [view] and its children. */
+        fun findBackground(view: View): Drawable? {
+            if (view.background != null) {
+                return view.background
+            }
+
+            // Perform a BFS to find the largest View with background.
+            val views = LinkedList<View>().apply {
+                add(view)
+            }
+
+            while (views.isNotEmpty()) {
+                val v = views.removeFirst()
+                if (v.background != null) {
+                    return v.background
+                }
+
+                if (v is ViewGroup) {
+                    for (i in 0 until v.childCount) {
+                        views.add(v.getChildAt(i))
+                    }
+                }
+            }
+
+            return null
+        }
+
+        background = findBackground(ghostedView)
+    }
 
     /**
      * Set the corner radius of [background]. The background is the one that was returned by
@@ -113,7 +144,7 @@ open class GhostedViewLaunchAnimatorController(
 
     /** Return the current top corner radius of the background. */
     protected open fun getCurrentTopCornerRadius(): Float {
-        val drawable = getBackground() ?: return 0f
+        val drawable = background ?: return 0f
         val gradient = findGradientDrawable(drawable) ?: return 0f
 
         // TODO(b/184121838): Support more than symmetric top & bottom radius.
@@ -122,7 +153,7 @@ open class GhostedViewLaunchAnimatorController(
 
     /** Return the current bottom corner radius of the background. */
     protected open fun getCurrentBottomCornerRadius(): Float {
-        val drawable = getBackground() ?: return 0f
+        val drawable = background ?: return 0f
         val gradient = findGradientDrawable(drawable) ?: return 0f
 
         // TODO(b/184121838): Support more than symmetric top & bottom radius.
@@ -162,9 +193,8 @@ open class GhostedViewLaunchAnimatorController(
 
         // We wrap the ghosted view background and use it to draw the expandable background. Its
         // alpha will be set to 0 as soon as we start drawing the expanding background.
-        val drawable = getBackground()
-        startBackgroundAlpha = drawable?.alpha ?: 0xFF
-        backgroundDrawable = WrappedDrawable(drawable)
+        startBackgroundAlpha = background?.alpha ?: 0xFF
+        backgroundDrawable = WrappedDrawable(background)
         backgroundView?.background = backgroundDrawable
 
         // Create a ghost of the view that will be moving and fading out. This allows to fade out