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Commit e3c540ad authored by Jordan Demeulenaere's avatar Jordan Demeulenaere
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Prevent NPE when placing fading elements 

This CL fixes an NPE that can happen since http://ag/27685078: the
placeWithLayer block can still run even if an element is removed from
composition.

Bug: 290930950
Test: Manual. Unfortunately it's impossible to add tests for this
 because the timings solely depend on the invalidation of the graphics
 layer by the Compose runtime. I have not observed the NPE with this
 change, but I also didn't have manual reproduction steps.
Flag: com.android.systemui.scene_container
Change-Id: Ic8bd91b3d6fd3f8b3d697c72a42bb5f278f5d207
parent 906dad1c

packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/Element.kt

+9 −5
Original line number Diff line number Diff line
@@ -381,11 +381,15 @@ internal class ElementNode( 
            } else {

                placeable.placeWithLayer(offset) {

                    // This layer might still run on its own (outside of the placement phase) even

                    // if this element is not placed anymore, so we need to double check again here

                    // before calling [elementAlpha] (which will update [SceneState.lastAlpha]). We

                    // also need to recompute the current transition to make sure that we are using

                    // the current transition and not a reference to an old one. See b/343138966 for

                    // details.

                    // if this element is not placed or composed anymore, so we need to double check

                    // again here before calling [elementAlpha] (which will update

                    // [SceneState.lastAlpha]). We also need to recompute the current transition to

                    // make sure that we are using the current transition and not a reference to an

                    // old one. See b/343138966 for details.

                    if (_element == null) {

                        return@placeWithLayer

                    }



                    val transition = elementTransition(layoutImpl, element, currentTransitions)

                    if (!shouldPlaceElement(layoutImpl, scene.key, element, transition)) {

                        return@placeWithLayer