Actually call LauncherTransitionable.onLauncherTransitionStep().

Previously, it was only called at the start and end of the transition;
now it is called as the animation interpolates. Specifically, a dummy
ValueAnimator is played alongside the transition animation and calls
dispatchOnLauncherTransitionStep() as it goes.

One place where this is important is in Workspace, where
mTransitionProgress is used to determine things like whether the
workspace should accept a drop - hence the bug that caused apps dragged
from All Apps to vanish when dropped before the transition ended.

Bug: 24215358
Change-Id: I32cd633c53557305caf84e87c9a4d4f07eef2223

src/com/android/launcher3/Launcher.java

@@ -3824,6 +3824,7 @@ public class Launcher extends Activity
      *
      * Implementation of the method from LauncherModel.Callbacks.
      */
+    @Override
     public void bindItems(final ArrayList<ItemInfo> shortcuts, final int start, final int end,
                           final boolean forceAnimateIcons) {
         Runnable r = new Runnable() {

src/com/android/launcher3/LauncherAnimUtils.java

@@ -24,7 +24,6 @@ import android.animation.ValueAnimator;
 import android.annotation.TargetApi;
 import android.os.Build;
 import android.view.View;
-import android.view.ViewAnimationUtils;
 import android.view.ViewTreeObserver;
 
 import com.android.launcher3.util.UiThreadCircularReveal;
@@ -59,24 +58,25 @@ public class LauncherAnimUtils {
     // it should be cancelled
     public static void startAnimationAfterNextDraw(final Animator animator, final View view) {
         view.getViewTreeObserver().addOnDrawListener(new ViewTreeObserver.OnDrawListener() {
-                private boolean mStarted = false;
-                public void onDraw() {
-                    if (mStarted) return;
-                    mStarted = true;
-                    // Use this as a signal that the animation was cancelled
-                    if (animator.getDuration() == 0) {
-                        return;
-                    }
-                    animator.start();
+            private boolean mStarted = false;
 
-                    final ViewTreeObserver.OnDrawListener listener = this;
-                    view.post(new Runnable() {
-                            public void run() {
-                                view.getViewTreeObserver().removeOnDrawListener(listener);
-                            }
-                        });
+            public void onDraw() {
+                if (mStarted) return;
+                mStarted = true;
+                // Use this as a signal that the animation was cancelled
+                if (animator.getDuration() == 0) {
+                    return;
                 }
-            });
+                animator.start();
+
+                final ViewTreeObserver.OnDrawListener listener = this;
+                view.post(new Runnable() {
+                    public void run() {
+                        view.getViewTreeObserver().removeOnDrawListener(listener);
+                    }
+                });
+            }
+        });
     }
 
     public static void onDestroyActivity() {

src/com/android/launcher3/LauncherStateTransitionAnimation.java

@@ -22,6 +22,7 @@ import android.animation.AnimatorSet;
 import android.animation.ObjectAnimator;
 import android.animation.PropertyValuesHolder;
 import android.animation.TimeInterpolator;
+import android.animation.ValueAnimator;
 import android.annotation.SuppressLint;
 import android.content.res.Resources;
 import android.util.Log;
@@ -229,6 +230,8 @@ public class LauncherStateTransitionAnimation {
         startWorkspaceSearchBarAnimation(animation, fromWorkspaceState, toWorkspaceState,
                 animated ? revealDuration : 0, overlaySearchBarView);
 
+        Animator updateTransitionStepAnim = dispatchOnLauncherTransitionStepAnim(fromView, toView);
+
         if (animated && initialized) {
             // Setup the reveal view animation
             int width = revealView.getMeasuredWidth();
@@ -342,11 +345,12 @@ public class LauncherStateTransitionAnimation {
                 animation.play(workspaceAnim);
             }
 
+            animation.play(updateTransitionStepAnim);
+
             // Dispatch the prepare transition signal
             dispatchOnLauncherTransitionPrepare(fromView, animated, false);
             dispatchOnLauncherTransitionPrepare(toView, animated, false);
 
-
             final AnimatorSet stateAnimation = animation;
             final Runnable startAnimRunnable = new Runnable() {
                 public void run() {
@@ -401,6 +405,24 @@ public class LauncherStateTransitionAnimation {
         }
     }
 
+    /**
+     * Returns an Animator that calls {@link #dispatchOnLauncherTransitionStep(View, float)} on
+     * {@param fromView} and {@param toView} as the animation interpolates.
+     *
+     * This is a bit hacky: we create a dummy ValueAnimator just for the AnimatorUpdateListener.
+     */
+    private Animator dispatchOnLauncherTransitionStepAnim(final View fromView, final View toView) {
+        ValueAnimator updateAnimator = ValueAnimator.ofFloat(0, 1);
+        updateAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
+            @Override
+            public void onAnimationUpdate(ValueAnimator animation) {
+                dispatchOnLauncherTransitionStep(fromView, animation.getAnimatedFraction());
+                dispatchOnLauncherTransitionStep(toView, animation.getAnimatedFraction());
+            }
+        });
+        return updateAnimator;
+    }
+
     /**
      * Starts and animation to the workspace from the apps view.
      */
@@ -509,12 +531,16 @@ public class LauncherStateTransitionAnimation {
         startWorkspaceSearchBarAnimation(animation, fromWorkspaceState, toWorkspaceState,
                 animated ? revealDuration : 0, overlaySearchBarView);
 
+        Animator updateTransitionStepAnim = dispatchOnLauncherTransitionStepAnim(fromView, toView);
+
         if (animated && initialized) {
             // Play the workspace animation
             if (workspaceAnim != null) {
                 animation.play(workspaceAnim);
             }
 
+            animation.play(updateTransitionStepAnim);
+
             // hideAppsCustomizeHelper is called in some cases when it is already hidden
             // don't perform all these no-op animations. In particularly, this was causing
             // the all-apps button to pop in and out.