Separate ExpandableWidget and ExpandableTransformationWidget.

Separate ExpandableBehavior and ExpandableTransformationBehavior.

ExpandableWidget - for widgets that have expanded state, like BackLayerLayout:
{g,s}etExpanded()
on{Save,Restore}InstanceState()

ExpandableBehavior - for behaviors that want to react to expanded state change, like BackLayerSiblingBehavior:
onLayoutChild() // Layouts the content, and animates the content to a new expanded position when BLL's expanded children change size.
onExpandedStateChange() // Animates the content position when expanded state changes.

ExpandableTransformationWidget - for widgets that transform during expansion, like FAB:
{g,s}etExpandedComponentIdHint()
Will also include these in the future:
getBackgroundDrawable() // Shape drawable includes color, bounds, shape, elevation
getForegroundDrawable()
etc

ExpandableTransformationBehavior - for behaviors that want to react to expanded state change by transforming, like FabTransformationSheetBehavior:
onCreateExpandedStateChangeAnimation() // Animates the FAB and sheet when expanded state changes.

PiperOrigin-RevId: 162809090

lib/src/android/support/design/stateful/ExtendableSavedState.java

@@ -16,23 +16,21 @@
 
 package android.support.design.stateful;
 
-import static android.support.annotation.RestrictTo.Scope.LIBRARY_GROUP;
-
 import android.os.Bundle;
 import android.os.Parcel;
 import android.os.Parcelable;
-import android.support.annotation.RestrictTo;
 import android.support.v4.util.SimpleArrayMap;
 import android.support.v4.view.AbsSavedState;
 
 /**
- * Class for widgets that want to save and restore their own state in {@link
+ * SavedState for widgets that want to save and restore their own state in {@link
  * android.view.View#onSaveInstanceState()}. Supports widgets whose state is composed or delegated
  * out to multiple components.
  *
- * @hide
+ * <p>Widgets with only composed or delegated state can directly instantiate this class and write to
+ * {@link #extendableStates}. Widgets with additional state should subclass ExtendableSavedState
+ * rather than trying to force the additional state into {@link #extendableStates}.
  */
-@RestrictTo(LIBRARY_GROUP)
 public class ExtendableSavedState extends AbsSavedState {
 
   public final SimpleArrayMap<String, Bundle> extendableStates;

lib/src/android/support/design/widget/FloatingActionButton.java

@@ -38,7 +38,7 @@ import android.support.annotation.VisibleForTesting;
 import android.support.design.R;
 import android.support.design.stateful.ExtendableSavedState;
 import android.support.design.widget.FloatingActionButtonImpl.InternalVisibilityChangedListener;
-import android.support.design.widget.expandable.ExpandableWidget;
+import android.support.design.widget.expandable.ExpandableTransformationWidget;
 import android.support.design.widget.expandable.ExpandableWidgetHelper;
 import android.support.v4.view.ViewCompat;
 import android.support.v7.widget.AppCompatImageHelper;
@@ -69,9 +69,11 @@ import java.util.List;
  * #setBackgroundTintList(ColorStateList)}.
  */
 @CoordinatorLayout.DefaultBehavior(FloatingActionButton.Behavior.class)
-public class FloatingActionButton extends VisibilityAwareImageButton implements ExpandableWidget {
+public class FloatingActionButton extends VisibilityAwareImageButton
+    implements ExpandableTransformationWidget {
 
   private static final String LOG_TAG = "FloatingActionButton";
+  private static final String EXPANDABLE_WIDGET_HELPER_KEY = "expandableWidgetHelper";
 
   /** Callback to be invoked when the visibility of a FloatingActionButton changes. */
   public abstract static class OnVisibilityChangedListener {
@@ -359,8 +361,8 @@ public class FloatingActionButton extends VisibilityAwareImageButton implements
   }
 
   @Override
-  public void setExpanded(boolean expanded) {
-    expandableWidgetHelper.setExpanded(expanded);
+  public boolean setExpanded(boolean expanded) {
+    return expandableWidgetHelper.setExpanded(expanded);
   }
 
   @Override
@@ -501,18 +503,18 @@ public class FloatingActionButton extends VisibilityAwareImageButton implements
   }
 
   @Override
-  protected Parcelable onSaveInstanceState() {
+  public Parcelable onSaveInstanceState() {
     Parcelable superState = super.onSaveInstanceState();
     ExtendableSavedState state = new ExtendableSavedState(superState);
 
     state.extendableStates.put(
-        "expandableWidgetHelper", expandableWidgetHelper.onSaveInstanceState());
+        EXPANDABLE_WIDGET_HELPER_KEY, expandableWidgetHelper.onSaveInstanceState());
 
     return state;
   }
 
   @Override
-  protected void onRestoreInstanceState(Parcelable state) {
+  public void onRestoreInstanceState(Parcelable state) {
     if (!(state instanceof ExtendableSavedState)) {
       super.onRestoreInstanceState(state);
       return;
@@ -522,7 +524,7 @@ public class FloatingActionButton extends VisibilityAwareImageButton implements
     super.onRestoreInstanceState(ess.getSuperState());
 
     expandableWidgetHelper.onRestoreInstanceState(
-        ess.extendableStates.get("expandableWidgetHelper"));
+        ess.extendableStates.get(EXPANDABLE_WIDGET_HELPER_KEY));
   }
 
   /**

lib/src/android/support/design/widget/expandable/ExpandableTransformationWidget.java

@@ -0,0 +1,35 @@
+/*
+ * Copyright 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package android.support.design.widget.expandable;
+
+import android.support.annotation.IdRes;
+
+/**
+ * An ExpandableWidget that visually transforms into another component when expanded.
+ */
+
+public interface ExpandableTransformationWidget extends ExpandableWidget {
+
+  /** Returns the expanded component id hint. */
+  @IdRes
+  int getExpandedComponentIdHint();
+
+  /**
+   * Sets the expanded component id hint, which may be used by a Behavior to determine whether it
+   * should handle this widget's state change.
+   */
+  void setExpandedComponentIdHint(@IdRes int expandedComponentIdHint);
+}

lib/src/android/support/design/widget/expandable/ExpandableWidget.java

@@ -16,29 +16,85 @@
 
 package android.support.design.widget.expandable;
 
-import android.support.annotation.IdRes;
+import android.os.Bundle;
+import android.os.Parcelable;
 
 /**
- * A widget that has expanded/collapsed state.
+ * A widget that has expanded/collapsed state. The state is saved across configuration changes. When
+ * the expanded state changes, {@link
+ * android.support.design.widget.CoordinatorLayout#dispatchDependentViewsChanged an event is
+ * dispatched} so that other widgets may react via a {@link
+ * android.support.design.widget.CoordinatorLayout.Behavior}.
  *
- * <p>When the expanded state changes, an event is dispatched so that other widgets may react via a
- * {@link android.support.design.widget.CoordinatorLayout.Behavior}.
+ * <p>Implementations of this interface should create an instance of {@link ExpandableWidgetHelper}
+ * and forward all calls to it.
  */
 public interface ExpandableWidget {
 
-  /** Returns whether this widget is expanded. */
+  /**
+   * Returns whether this widget is expanded.
+   *
+   * <p>Implementations should call {@link ExpandableWidgetHelper#isExpanded()}.
+   */
   boolean isExpanded();
 
-  /** Sets the expanded state on this widget. */
-  void setExpanded(boolean expanded);
-
-  /** Returns the expanded component id hint. */
-  @IdRes
-  int getExpandedComponentIdHint();
+  /**
+   * Sets the expanded state on this widget.
+   *
+   * <p>Implementations should call {@link ExpandableWidgetHelper#setExpanded(boolean)}.
+   *
+   * @return true if the expanded state changed as a result of this call.
+   */
+  boolean setExpanded(boolean expanded);
 
   /**
-   * Sets the expanded component id hint, which may be used by a Behavior to determine whether it
-   * should handle this widget's state change.
+   * Saves the expanded state on configuration change.
+   *
+   * <p>Implementations should call {@link ExpandableWidgetHelper#onSaveInstanceState()} and save
+   * the returned state along with the widget state.
+   *
+   * <p>For a correct implementation of this, use an {@link
+   * android.support.design.stateful.ExtendableSavedState}. See its class javadoc for more details.
+   *
+   * <pre><code>
+   * {@literal @}Override
+   * public Parcelable onSaveInstanceState() {
+   *   Parcelable superState = super.onSaveInstanceState();
+   *   ExtendableSavedState state = new ExtendableSavedState(superState);
+   *
+   *   state.extendableStates.put(
+   *       "expandableWidgetHelper", expandableWidgetHelper.onSaveInstanceState());
+   *
+   *   return state;
+   * }
+   * </code></pre>
    */
-  void setExpandedComponentIdHint(@IdRes int expandedComponentIdHint);
+  Parcelable onSaveInstanceState();
+
+  /**
+   * Restores the expanded state on configuration change.
+   *
+   * <p>Implementations should call {@link ExpandableWidgetHelper#onRestoreInstanceState(Bundle)} to
+   * restore the saved state along with the widget state.
+   *
+   * <p>For a correct implementation of this, use an {@link
+   * android.support.design.stateful.ExtendableSavedState}. See its class javadoc for more details.
+   *
+   * <pre><code>
+   * {@literal @}Override
+   * public void onRestoreInstanceState(Parcelable state) {
+   *   if (!(state instanceof ExtendableSavedState)) {
+   *     super.onRestoreInstanceState(state);
+   *     return;
+   *   }
+   *
+   *   ExtendableSavedState ess = (ExtendableSavedState) state;
+   *   super.onRestoreInstanceState(ess.getSuperState());
+   *
+   *   expandableWidgetHelper.onRestoreInstanceState(
+   *       ess.extendableStates.get("expandableWidgetHelper"));
+   * }
+   * </code></pre>
+   */
+  void onRestoreInstanceState(Parcelable state);
 }

lib/src/android/support/design/widget/expandable/ExpandableWidgetHelper.java

@@ -24,27 +24,30 @@ import android.view.View;
 import android.view.ViewParent;
 
 /**
- * ExpandableWidgetHelper is a helper class for writing custom {@link ExpandableWidget
- * ExpandableWidgets}. Please see each method's documentation when implementing your custom class.
+ * ExpandableWidgetHelper is a helper class for writing custom {@link ExpandableWidget}s and {@link
+ * ExpandableTransformationWidget}. Please see the interface documentation when implementing your
+ * custom class.
  */
 public final class ExpandableWidgetHelper {
 
   private final View widget;
 
-  private boolean expanded;
-  @IdRes private int expandedComponentIdHint;
+  private boolean expanded = false;
+  @IdRes private int expandedComponentIdHint = 0;
 
   /** Call this from the constructor. */
-  public <T extends View & ExpandableWidget> ExpandableWidgetHelper(T widget) {
-    this.widget = widget;
+  public ExpandableWidgetHelper(ExpandableWidget widget) {
+    this.widget = (View) widget;
   }
 
   /** Call this from {@link ExpandableWidget#setExpanded(boolean)}. */
-  public void setExpanded(boolean expanded) {
+  public boolean setExpanded(boolean expanded) {
     if (this.expanded != expanded) {
       this.expanded = expanded;
       dispatchExpandedStateChanged();
+      return true;
     }
+    return false;
   }
 
   /** Call this from {@link ExpandableWidget#isExpanded()}. */
@@ -52,20 +55,7 @@ public final class ExpandableWidgetHelper {
     return expanded;
   }
 
-  /** Call this from {@link ExpandableWidget#setExpandedComponentIdHint(int)}. */
-  public void setExpandedComponentIdHint(@IdRes int expandedComponentIdHint) {
-    this.expandedComponentIdHint = expandedComponentIdHint;
-  }
-
-  /** Call this from {@link ExpandableWidget#getExpandedComponentIdHint()}. */
-  @IdRes
-  public int getExpandedComponentIdHint() {
-    return expandedComponentIdHint;
-  }
-
-  /**
-   * Call this from {@link View#onSaveInstanceState()} after your widget's custom state is saved.
-   */
+  /** Call this from {@link ExpandableWidget#onSaveInstanceState()}. */
   public Bundle onSaveInstanceState() {
     Bundle state = new Bundle();
     state.putBoolean("expanded", expanded);
@@ -74,10 +64,7 @@ public final class ExpandableWidgetHelper {
     return state;
   }
 
-  /**
-   * Call this from {@link View#onRestoreInstanceState(Parcelable)} after your widget's custom state
-   * is restored.
-   */
+  /** Call this from {@link ExpandableWidget#onRestoreInstanceState(Parcelable)}. */
   public void onRestoreInstanceState(Bundle state) {
     expanded = state.getBoolean("expanded", false);
     expandedComponentIdHint = state.getInt("expandedComponentIdHint", 0);
@@ -87,6 +74,17 @@ public final class ExpandableWidgetHelper {
     }
   }
 
+  /** Call this from {@link ExpandableTransformationWidget#setExpandedComponentIdHint(int)}. */
+  public void setExpandedComponentIdHint(@IdRes int expandedComponentIdHint) {
+    this.expandedComponentIdHint = expandedComponentIdHint;
+  }
+
+  /** Call this from {@link ExpandableTransformationWidget#getExpandedComponentIdHint()}. */
+  @IdRes
+  public int getExpandedComponentIdHint() {
+    return expandedComponentIdHint;
+  }
+
   private void dispatchExpandedStateChanged() {
     ViewParent parent = widget.getParent();
     if (parent instanceof CoordinatorLayout) {

lib/src/android/support/design/widget/transformation/ExpandableBehavior.java

@@ -0,0 +1,146 @@
+/*
+ * Copyright 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package android.support.design.widget.transformation;
+
+import android.content.Context;
+import android.support.annotation.CallSuper;
+import android.support.annotation.IntDef;
+import android.support.annotation.Nullable;
+import android.support.design.widget.CoordinatorLayout;
+import android.support.design.widget.CoordinatorLayout.Behavior;
+import android.support.design.widget.expandable.ExpandableWidget;
+import android.support.v4.view.ViewCompat;
+import android.util.AttributeSet;
+import android.view.View;
+import android.view.ViewGroup;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.util.List;
+
+/**
+ * Base Behavior for views that can react to an {@link ExpandableWidget}'s {@link
+ * ExpandableWidget#setExpanded(boolean)} state changes.
+ */
+public abstract class ExpandableBehavior extends Behavior<View> {
+
+  /** Unknown expanded state. */
+  private static final int STATE_UNKNOWN = 0;
+  /** Expanded state. */
+  private static final int STATE_EXPANDED = 1;
+  /** Collapsed state. */
+  private static final int STATE_COLLAPSED = 2;
+
+  @IntDef({STATE_UNKNOWN, STATE_EXPANDED, STATE_COLLAPSED})
+  @Retention(RetentionPolicy.SOURCE)
+  private @interface State {}
+
+  /**
+   * The current expanded state of this behavior. This state follows the expanded state of the
+   * {@link ExpandableWidget} dependency, and is updated in {@link #onLayoutChild(CoordinatorLayout,
+   * View, int)} and {@link #onDependentViewChanged(CoordinatorLayout, View, View)}.
+   *
+   * <p>This state may be {@link #STATE_UNKNOWN} before either of those callbacks have been invoked.
+   */
+  @State private int currentState = STATE_UNKNOWN;
+
+  public ExpandableBehavior() {}
+
+  public ExpandableBehavior(Context context, AttributeSet attrs) {
+    super(context, attrs);
+  }
+
+  @Override
+  public abstract boolean layoutDependsOn(CoordinatorLayout parent, View child, View dependency);
+
+  /**
+   * Reacts to a change in expanded state. This callback is guaranteed to be called only once even
+   * if {@link ExpandableWidget#setExpanded(boolean)} is called multiple times with the same value.
+   * Upon configuration change, this callback is called with {@code animated} set to false.
+   *
+   * @param dependency the {@link ExpandableWidget} dependency containing the new expanded state.
+   * @param child the view that should react to the change in expanded state.
+   * @param expanded the new expanded state.
+   * @param animated true if {@link ExpandableWidget#setExpanded(boolean)} was called, false if
+   *     restoring from a configuration change.
+   * @return true if the Behavior changed the child view's size or position, false otherwise.
+   */
+  protected abstract boolean onExpandedStateChange(
+      ExpandableWidget dependency, View child, boolean expanded, boolean animated);
+
+  @CallSuper
+  @Override
+  public boolean onLayoutChild(CoordinatorLayout parent, View child, int layoutDirection) {
+    if (!ViewCompat.isLaidOut(child)) {
+      ExpandableWidget dep = findExpandableWidget(parent, child);
+      if (dep != null) {
+        currentState = dep.isExpanded() ? STATE_EXPANDED : STATE_COLLAPSED;
+        onExpandedStateChange(dep, child, dep.isExpanded(), false);
+      }
+    }
+
+    return false;
+  }
+
+  @CallSuper
+  @Override
+  public boolean onDependentViewChanged(CoordinatorLayout parent, View child, View dependency) {
+    ExpandableWidget dep = (ExpandableWidget) dependency;
+    boolean expanded = dep.isExpanded();
+    if (didStateChange(expanded)) {
+      currentState = dep.isExpanded() ? STATE_EXPANDED : STATE_COLLAPSED;
+      return onExpandedStateChange(dep, child, dep.isExpanded(), true);
+    }
+
+    return false;
+  }
+
+  @Nullable
+  protected ExpandableWidget findExpandableWidget(CoordinatorLayout parent, View child) {
+    List<View> dependencies = parent.getDependencies(child);
+    for (int i = 0, size = dependencies.size(); i < size; i++) {
+      View dependency = dependencies.get(i);
+      if (layoutDependsOn(parent, child, dependency)) {
+        return (ExpandableWidget) dependency;
+      }
+    }
+    return null;
+  }
+
+  private boolean didStateChange(boolean expanded) {
+    return (expanded && ((currentState == STATE_UNKNOWN) || (currentState == STATE_COLLAPSED)))
+        || (!expanded && ((currentState == STATE_UNKNOWN) || (currentState == STATE_EXPANDED)));
+  }
+
+  /**
+   * A utility function to get the {@link ExpandableBehavior} attached to the {@code view}.
+   *
+   * @param view The {@link View} that the {@link ExpandableBehavior} is attached to.
+   * @param klass The expected {@link Class} of the attached {@link ExpandableBehavior}.
+   * @return The {@link ExpandableBehavior} attached to the {@code view}.
+   */
+  public static <T extends ExpandableBehavior> T from(View view, Class<T> klass) {
+    ViewGroup.LayoutParams params = view.getLayoutParams();
+    if (!(params instanceof CoordinatorLayout.LayoutParams)) {
+      throw new IllegalArgumentException("The view is not a child of CoordinatorLayout");
+    }
+    CoordinatorLayout.Behavior<?> behavior =
+        ((CoordinatorLayout.LayoutParams) params).getBehavior();
+    if (!(behavior instanceof ExpandableBehavior)) {
+      throw new IllegalArgumentException("The view is not associated with ExpandableBehavior");
+    }
+    return klass.cast(behavior);
+  }
+}

lib/src/android/support/design/widget/transformation/ExpandableTransformationBehavior.java

@@ -19,44 +19,22 @@ package android.support.design.widget.transformation;
 import android.animation.Animator;
 import android.animation.AnimatorListenerAdapter;
 import android.content.Context;
-import android.support.annotation.IntDef;
+import android.support.annotation.CallSuper;
+import android.support.annotation.NonNull;
 import android.support.annotation.Nullable;
-import android.support.design.widget.CoordinatorLayout;
-import android.support.design.widget.CoordinatorLayout.Behavior;
 import android.support.design.widget.expandable.ExpandableWidget;
-import android.support.v4.view.ViewCompat;
 import android.util.AttributeSet;
 import android.view.View;
-import android.view.ViewGroup;
-import java.lang.annotation.Retention;
-import java.lang.annotation.RetentionPolicy;
-import java.util.List;
 
 /**
- * Base Behavior for views that a {@link ExpandableWidget} can transform into. Reacts to {@link
- * ExpandableWidget#setExpanded(boolean)} state changes with an animation.
+ * Base Behavior for views that can react to an {@link ExpandableWidget}'s {@link
+ * ExpandableWidget#setExpanded(boolean)} state changes by transforming the ExpandableWidget into
+ * itself.
+ *
+ * <p>Behaviors should override {@link #onCreateExpandedStateChangeAnimation(ExpandableWidget, View,
+ * boolean)} to return an animation
  */
-public abstract class ExpandableTransformationBehavior extends Behavior<View> {
-
-  /** Unknown expanded state. */
-  private static final int STATE_UNKNOWN = 0;
-  /** Expanded state. */
-  private static final int STATE_EXPANDED = 1;
-  /** Collapsed state. */
-  private static final int STATE_COLLAPSED = 2;
-
-  @IntDef({STATE_UNKNOWN, STATE_EXPANDED, STATE_COLLAPSED})
-  @Retention(RetentionPolicy.SOURCE)
-  private @interface State {}
-
-  /**
-   * The current expanded state of this behavior. This state follows the expanded state of the
-   * {@link ExpandableWidget} dependency, and is updated in {@link #onLayoutChild(CoordinatorLayout,
-   * View, int)} and {@link #onDependentViewChanged(CoordinatorLayout, View, View)}.
-   *
-   * <p>This state may be {@link #STATE_UNKNOWN} before either of those callbacks have been invoked.
-   */
-  @State private int currentState = STATE_UNKNOWN;
+public abstract class ExpandableTransformationBehavior extends ExpandableBehavior {
 
   @Nullable private Animator currentAnimation;
 
@@ -66,109 +44,46 @@ public abstract class ExpandableTransformationBehavior extends Behavior<View> {
     super(context, attrs);
   }
 
+  /**
+   * Creates an Animator to be played for this expanded state change.
+   *
+   * <p>If the new {@code expanded} state is true, the {@code dependency} should be hidden and the
+   * {@code child} should be shown.
+   *
+   * <p>If the new {@code expanded} state is false, the {@code dependency} should be shown and the
+   * {@code child} should be hidden.
+   *
+   * @param dependency the {@link ExpandableWidget} dependency containing the new expanded state.
+   * @param child the view that should react to the change in expanded state.
+   * @param expanded the new expanded state.
+   */
+  @NonNull
+  protected abstract Animator onCreateExpandedStateChangeAnimation(
+      ExpandableWidget dependency, View child, boolean expanded);
+
+  @CallSuper
   @Override
-  public boolean layoutDependsOn(CoordinatorLayout parent, View child, View dependency) {
-    return dependency instanceof ExpandableWidget;
-  }
-
-  @Override
-  public boolean onLayoutChild(CoordinatorLayout parent, View child, int layoutDirection) {
-    if (!ViewCompat.isLaidOut(child)) {
-      List<View> dependencies = parent.getDependencies(child);
-      ExpandableWidget dependency = findExpandableWidget(dependencies);
-      jumpToState(dependency, child);
-    }
-
-    return false;
-  }
-
-  @Override
-  public boolean onDependentViewChanged(CoordinatorLayout parent, View child, View dependency) {
-    ExpandableWidget dep = (ExpandableWidget) dependency;
-    boolean expanded = dep.isExpanded();
-    if (!didStateChange(expanded)) {
-      return false;
-    }
-
+  protected boolean onExpandedStateChange(
+      ExpandableWidget dependency, View child, boolean expanded, boolean animated) {
     if (currentAnimation != null) {
       currentAnimation.cancel();
     }
 
-    currentState = expanded ? STATE_EXPANDED : STATE_COLLAPSED;
-    currentAnimation = createAnimation(dep, child);
+    currentAnimation = onCreateExpandedStateChangeAnimation(dependency, child, expanded);
     currentAnimation.addListener(
         new AnimatorListenerAdapter() {
-          @Override
-          public void onAnimationStart(Animator animation) {
-            if (expanded) {
-              child.setVisibility(View.VISIBLE);
-            }
-          }
-
           @Override
           public void onAnimationEnd(Animator animation) {
-            if (!expanded) {
-              child.setVisibility(View.INVISIBLE);
-            }
             currentAnimation = null;
           }
         });
+
     currentAnimation.start();
+    if (!animated) {
+      // Synchronously end the animation, jumping to the end state.
+      currentAnimation.end();
+    }
+
     return true;
   }
-
-  protected void jumpToState(ExpandableWidget dep, View child) {
-    boolean expanded = dep.isExpanded();
-    if (!didStateChange(expanded)) {
-      return;
-    }
-
-    currentState = expanded ? STATE_EXPANDED : STATE_COLLAPSED;
-
-    if (expanded) {
-      child.setVisibility(View.VISIBLE);
-    } else {
-      child.setVisibility(View.INVISIBLE);
-    }
-  }
-
-  protected abstract Animator createAnimation(ExpandableWidget dep, View child);
-
-  private ExpandableWidget findExpandableWidget(List<View> dependencies) {
-    for (int i = 0, size = dependencies.size(); i < size; i++) {
-      View dependency = dependencies.get(i);
-      if (dependency instanceof ExpandableWidget) {
-        return (ExpandableWidget) dependency;
-      }
-    }
-    return null;
-  }
-
-  private boolean didStateChange(boolean expanded) {
-    return (expanded && ((currentState == STATE_UNKNOWN) || (currentState == STATE_COLLAPSED)))
-        || (!expanded && ((currentState == STATE_UNKNOWN) || (currentState == STATE_EXPANDED)));
-  }
-
-  /**
-   * A utility function to get the {@link ExpandableTransformationBehavior} attached to the {@code
-   * view}.
-   *
-   * @param view The {@link View} that the {@link ExpandableTransformationBehavior} is attached to.
-   * @param klass The expected {@link Class} of the attached {@link
-   *     ExpandableTransformationBehavior}.
-   * @return The {@link ExpandableTransformationBehavior} attached to the {@code view}.
-   */
-  public static <T extends ExpandableTransformationBehavior> T from(View view, Class<T> klass) {
-    ViewGroup.LayoutParams params = view.getLayoutParams();
-    if (!(params instanceof CoordinatorLayout.LayoutParams)) {
-      throw new IllegalArgumentException("The view is not a child of CoordinatorLayout");
-    }
-    CoordinatorLayout.Behavior<?> behavior =
-        ((CoordinatorLayout.LayoutParams) params).getBehavior();
-    if (!(behavior instanceof ExpandableTransformationBehavior)) {
-      throw new IllegalArgumentException(
-          "The view is not associated with ExpandableTransformationBehavior");
-    }
-    return klass.cast(view);
-  }
 }

lib/src/android/support/design/widget/transformation/FabTransformationScrimBehavior.java

@@ -17,9 +17,11 @@
 package android.support.design.widget.transformation;
 
 import android.animation.Animator;
+import android.animation.AnimatorListenerAdapter;
 import android.animation.AnimatorSet;
 import android.animation.ObjectAnimator;
 import android.content.Context;
+import android.support.annotation.NonNull;
 import android.support.design.widget.CoordinatorLayout;
 import android.support.design.widget.FloatingActionButton;
 import android.support.design.widget.expandable.ExpandableWidget;
@@ -30,8 +32,8 @@ import java.util.ArrayList;
 import java.util.List;
 
 /**
- * Behavior that should be attached to a scrim that should appear when a {@link ExpandableWidget} is
- * {@link ExpandableWidget#setExpanded(boolean)} expanded}.
+ * Behavior that should be attached to a scrim that should appear when a {@link
+ * FloatingActionButton} is {@link FloatingActionButton#setExpanded(boolean)} expanded}.
  */
 public class FabTransformationScrimBehavior extends ExpandableTransformationBehavior {
 
@@ -44,8 +46,7 @@ public class FabTransformationScrimBehavior extends ExpandableTransformationBeha
 
   @Override
   public boolean layoutDependsOn(CoordinatorLayout parent, View child, View dependency) {
-    return super.layoutDependsOn(parent, child, dependency)
-        && dependency instanceof FloatingActionButton;
+    return dependency instanceof FloatingActionButton;
   }
 
   @Override
@@ -54,17 +55,35 @@ public class FabTransformationScrimBehavior extends ExpandableTransformationBeha
     return super.onTouchEvent(parent, child, ev);
   }
 
+  @NonNull
   @Override
-  protected Animator createAnimation(ExpandableWidget dep, View child) {
+  protected Animator onCreateExpandedStateChangeAnimation(
+      ExpandableWidget dep, View child, boolean expanded) {
     List<Animator> animations = new ArrayList<>();
 
-    if (dep.isExpanded()) {
+    if (expanded) {
       animations.add(ObjectAnimator.ofFloat(child, View.ALPHA, 0f, 1f));
     } else {
       animations.add(ObjectAnimator.ofFloat(child, View.ALPHA, 1f, 0f));
     }
 
     AnimatorSet set = new AnimatorSet();
+    set.addListener(
+        new AnimatorListenerAdapter() {
+          @Override
+          public void onAnimationStart(Animator animation) {
+            if (expanded) {
+              child.setVisibility(View.VISIBLE);
+            }
+          }
+
+          @Override
+          public void onAnimationEnd(Animator animation) {
+            if (!expanded) {
+              child.setVisibility(View.INVISIBLE);
+            }
+          }
+        });
     set.playTogether(animations);
     return set;
   }

lib/src/android/support/design/widget/transformation/FabTransformationSheetBehavior.java

@@ -32,8 +32,8 @@ import java.util.ArrayList;
 import java.util.List;
 
 /**
- * Behavior that should be attached to any sheet that should appear when a {@link ExpandableWidget}
- * is {@link ExpandableWidget#setExpanded(boolean)} expanded}.
+ * Behavior that should be attached to any sheet that should appear when a {@link
+ * FloatingActionButton} is {@link FloatingActionButton#setExpanded(boolean)} expanded}.
  *
  * <p>A sheet usually has some width and height that's smaller than the screen, has an elevation,
  * and may have a scrim underneath.
@@ -49,8 +49,7 @@ public class FabTransformationSheetBehavior extends ExpandableTransformationBeha
 
   @Override
   public boolean layoutDependsOn(CoordinatorLayout parent, View child, View dependency) {
-    return super.layoutDependsOn(parent, child, dependency)
-        && dependency instanceof FloatingActionButton;
+    return dependency instanceof FloatingActionButton;
   }
 
   @Override
@@ -62,32 +61,18 @@ public class FabTransformationSheetBehavior extends ExpandableTransformationBeha
     }
   }
 
+  @NonNull
   @Override
-  protected void jumpToState(ExpandableWidget dep, View child) {
-    super.jumpToState(dep, child);
-
-    View dependency = (View) dep;
-    if (dep.isExpanded()) {
-      // A bug exists in 4.4.4 where setVisibility() did not invalidate the view.
-      dependency.setAlpha(0f);
-      dependency.setVisibility(View.INVISIBLE);
-    } else {
-      // A bug exists in 4.4.4 where setVisibility() did not invalidate the view.
-      dependency.setAlpha(1f);
-      dependency.setVisibility(View.VISIBLE);
-    }
-  }
-
-  @Override
-  protected Animator createAnimation(ExpandableWidget dep, View child) {
+  protected Animator onCreateExpandedStateChangeAnimation(
+      ExpandableWidget dependency, View child, boolean expanded) {
     List<Animator> animations = new ArrayList<>();
 
-    View dependency = (View) dep;
-    if (dep.isExpanded()) {
-      animations.add(ObjectAnimator.ofFloat(dependency, View.ALPHA, 1f, 0f));
+    View dep = (View) dependency;
+    if (expanded) {
+      animations.add(ObjectAnimator.ofFloat(dep, View.ALPHA, 1f, 0f));
       animations.add(ObjectAnimator.ofFloat(child, View.ALPHA, 0f, 1f));
     } else {
-      animations.add(ObjectAnimator.ofFloat(dependency, View.ALPHA, 0f, 1f));
+      animations.add(ObjectAnimator.ofFloat(dep, View.ALPHA, 0f, 1f));
       animations.add(ObjectAnimator.ofFloat(child, View.ALPHA, 1f, 0f));
     }
 
@@ -97,19 +82,23 @@ public class FabTransformationSheetBehavior extends ExpandableTransformationBeha
         new AnimatorListenerAdapter() {
           @Override
           public void onAnimationStart(Animator animation) {
-            if (!dep.isExpanded()) {
+            if (expanded) {
+              child.setVisibility(View.VISIBLE);
+            } else {
               // A bug exists in 4.4.4 where setVisibility() did not invalidate the view.
-              dependency.setAlpha(1f);
-              dependency.setVisibility(View.VISIBLE);
+              dep.setAlpha(1f);
+              dep.setVisibility(View.VISIBLE);
             }
           }
 
           @Override
           public void onAnimationEnd(Animator animation) {
-            if (dep.isExpanded()) {
+            if (expanded) {
               // A bug exists in 4.4.4 where setVisibility() did not invalidate the view.
-              dependency.setAlpha(0f);
-              dependency.setVisibility(View.INVISIBLE);
+              dep.setAlpha(0f);
+              dep.setVisibility(View.INVISIBLE);
+            } else {
+              child.setVisibility(View.INVISIBLE);
             }
           }
         });