Fade navbar-handle in/out during TRANSITION_HANDLE_FADE

The existing code relied on the INSTANT / FINAL_FRAME interpolators,
however these did not work as expected for sub-animations with shorter durations,
since the INSTANT / FINAL_FRAME interpolator applies to the sub-animations durations

This caused the stashed handle to jumpcut in/out, while the taskbar icons were
actually visible in the area of the navbar.

This is fixed to polish the lock/unlock animation (b/275319714), but happenes to fix b/276941963 as well.

Before: http://shortn/_uxw2oe7QeA
After: http://shortn/_yMY8IQIM60

Bug: 275319714
Bug: 276941963
Fixed: 275319714
Fixed: 276941963

Test: manual (http://shortn/_rnGNSkRH3w), tapl tests
Change-Id: I79e431e9ee21ede069864ee217bb343f0c32dfc7
diff --git a/quickstep/src/com/android/launcher3/taskbar/TaskbarStashController.java b/quickstep/src/com/android/launcher3/taskbar/TaskbarStashController.java
index f675b57..69ea9fd 100644
--- a/quickstep/src/com/android/launcher3/taskbar/TaskbarStashController.java
+++ b/quickstep/src/com/android/launcher3/taskbar/TaskbarStashController.java
@@ -749,56 +749,77 @@
 
     private void createTransientAnimToIsStashed(AnimatorSet as, boolean isStashed, long duration,
             @StashAnimation int animationType) {
-        Interpolator skipInterpolator = null;
+        // Target values of the properties this is going to set
+        final float backgroundOffsetTarget = isStashed ? 1 : 0;
+        final float iconAlphaTarget = isStashed ? 0 : 1;
+        final float stashedHandleAlphaTarget = isStashed ? 1 : 0;
+
+        // Timing for the alpha values depend on the animation played
+        long iconAlphaStartDelay = 0, iconAlphaDuration = 0, stashedHandleAlphaDelay = 0,
+                stashedHandleAlphaDuration = 0;
+        if (duration > 0) {
+            if (animationType == TRANSITION_HANDLE_FADE) {
+                // When fading, the handle fades in/out at the beginning of the transition with
+                // TASKBAR_STASH_ALPHA_DURATION.
+                stashedHandleAlphaDuration = TASKBAR_STASH_ALPHA_DURATION;
+                // The iconAlphaDuration must be set to duration for the skippable interpolators
+                // below to work.
+                iconAlphaDuration = duration;
+            } else {
+                iconAlphaStartDelay = TASKBAR_STASH_ALPHA_START_DELAY;
+                iconAlphaDuration = TASKBAR_STASH_ALPHA_DURATION;
+                stashedHandleAlphaDuration = TASKBAR_STASH_ALPHA_DURATION;
+
+                if (isStashed) {
+                    if (animationType == TRANSITION_HOME_TO_APP) {
+                        iconAlphaStartDelay = TASKBAR_STASH_ICON_ALPHA_HOME_TO_APP_START_DELAY;
+                    }
+                    stashedHandleAlphaDelay = iconAlphaStartDelay;
+                    stashedHandleAlphaDuration = Math.max(0, duration - iconAlphaStartDelay);
+                }
+
+            }
+        }
+
+        play(as, mTaskbarStashedHandleAlpha.animateToValue(stashedHandleAlphaTarget),
+                stashedHandleAlphaDelay,
+                stashedHandleAlphaDuration, LINEAR);
+
+        // The rest of the animations might be "skipped" in TRANSITION_HANDLE_FADE transitions.
+        AnimatorSet skippable = as;
+        if (animationType == TRANSITION_HANDLE_FADE) {
+            skippable = new AnimatorSet();
+            as.play(skippable);
+            skippable.setInterpolator(isStashed ? INSTANT : FINAL_FRAME);
+        }
+
+        final boolean animateBg = animationType != TRANSITION_UNSTASH_SUW_MANUAL;
+        if (animateBg) {
+            play(skippable, mTaskbarBackgroundOffset.animateToValue(backgroundOffsetTarget), 0,
+                    duration, EMPHASIZED);
+        } else {
+            skippable.addListener(AnimatorListeners.forEndCallback(
+                    () -> mTaskbarBackgroundOffset.updateValue(backgroundOffsetTarget)));
+        }
+
+        play(skippable, mIconAlphaForStash.animateToValue(iconAlphaTarget), iconAlphaStartDelay,
+                iconAlphaDuration,
+                LINEAR);
 
         if (isStashed) {
-            play(as, mTaskbarBackgroundOffset.animateToValue(1), 0, duration, EMPHASIZED);
-
-            long alphaStartDelay = duration == 0 ? 0 : animationType == TRANSITION_HOME_TO_APP
-                    ? TASKBAR_STASH_ICON_ALPHA_HOME_TO_APP_START_DELAY
-                    : TASKBAR_STASH_ALPHA_START_DELAY;
-            long alphaDuration = duration == 0 ? 0 : TASKBAR_STASH_ALPHA_DURATION;
-            play(as, mIconAlphaForStash.animateToValue(0), alphaStartDelay, alphaDuration, LINEAR);
-            play(as, mTaskbarStashedHandleAlpha.animateToValue(1), alphaStartDelay,
-                    Math.max(0, duration - alphaStartDelay), LINEAR);
-
-            play(as, mControllers.taskbarSpringOnStashController.createSpringToStash(), 0, duration,
-                    LINEAR);
-
-            if (animationType == TRANSITION_HANDLE_FADE) {
-                skipInterpolator = INSTANT;
-            }
-        } else  {
-            final boolean animateBg = animationType != TRANSITION_UNSTASH_SUW_MANUAL;
-            if (animateBg) {
-                play(as, mTaskbarBackgroundOffset.animateToValue(0), 0, duration, EMPHASIZED);
-            } else {
-                as.addListener(AnimatorListeners.forEndCallback(
-                        () -> mTaskbarBackgroundOffset.updateValue(0)));
-            }
-
-            long alphaStartDelay = duration == 0 ? 0 : TASKBAR_STASH_ALPHA_START_DELAY;
-            long alphaDuration = duration == 0 ? 0 : TASKBAR_STASH_ALPHA_DURATION;
-            play(as, mIconAlphaForStash.animateToValue(1), alphaStartDelay, alphaDuration, LINEAR);
-            play(as, mTaskbarStashedHandleAlpha.animateToValue(0), 0, alphaDuration, LINEAR);
-
-            if (animationType == TRANSITION_HANDLE_FADE) {
-                skipInterpolator = FINAL_FRAME;
-            }
+            play(skippable, mControllers.taskbarSpringOnStashController.createSpringToStash(),
+                    0, duration, LINEAR);
         }
-        mControllers.taskbarViewController.addRevealAnimToIsStashed(as, isStashed, duration,
+
+        mControllers.taskbarViewController.addRevealAnimToIsStashed(skippable, isStashed, duration,
                 EMPHASIZED);
 
-        if (skipInterpolator != null) {
-            as.setInterpolator(skipInterpolator);
-        }
-
-        play(as, mControllers.stashedHandleViewController
+        play(skippable, mControllers.stashedHandleViewController
                 .createRevealAnimToIsStashed(isStashed), 0, duration, EMPHASIZED);
 
         // Return the stashed handle to its default scale in case it was changed as part of the
         // feedforward hint. Note that the reveal animation above also visually scales it.
-        as.play(mTaskbarStashedHandleHintScale.animateToValue(1f)
+        skippable.play(mTaskbarStashedHandleHintScale.animateToValue(1f)
                 .setDuration(isStashed ? duration / 2 : duration));
     }