Update BottomAppBar hideOnScroll offset to account for the shadow drawn at the top of the view.

PiperOrigin-RevId: 250562675

Author: cketcham

lib/java/com/google/android/material/behavior/HideBottomViewOnScrollBehavior.java

@@ -43,6 +43,7 @@ public class HideBottomViewOnScrollBehavior<V extends View> extends CoordinatorL
 
   private int height = 0;
   private int currentState = STATE_SCROLLED_UP;
+  private int additionalHiddenOffsetY = 0;
   private ViewPropertyAnimator currentAnimator;
 
   public HideBottomViewOnScrollBehavior() {}
@@ -59,6 +60,15 @@ public boolean onLayoutChild(CoordinatorLayout parent, V child, int layoutDirect
     return super.onLayoutChild(parent, child, layoutDirection);
   }
 
+  /** Sets an additional offset for the y position used to hide the view. */
+  public void setAdditionalHiddenOffsetY(V child, int offset) {
+    additionalHiddenOffsetY = offset;
+
+    if (currentState == STATE_SCROLLED_DOWN) {
+      child.setTranslationY(height + additionalHiddenOffsetY);
+    }
+  }
+
   @Override
   public boolean onStartNestedScroll(
       CoordinatorLayout coordinatorLayout,
@@ -78,9 +88,9 @@ public void onNestedScroll(
       int dyConsumed,
       int dxUnconsumed,
       int dyUnconsumed) {
-    if (currentState != STATE_SCROLLED_DOWN && dyConsumed > 0) {
+    if (dyConsumed > 0) {
       slideDown(child);
-    } else if (currentState != STATE_SCROLLED_UP && dyConsumed < 0) {
+    } else if (dyConsumed < 0) {
       slideUp(child);
     }
   }
@@ -90,6 +100,10 @@ public void onNestedScroll(
    * screen.
    */
   public void slideUp(V child) {
+    if (currentState == STATE_SCROLLED_UP) {
+      return;
+    }
+
     if (currentAnimator != null) {
       currentAnimator.cancel();
       child.clearAnimation();
@@ -104,13 +118,20 @@ public void slideUp(V child) {
    * screen.
    */
   public void slideDown(V child) {
+    if (currentState == STATE_SCROLLED_DOWN) {
+      return;
+    }
+
     if (currentAnimator != null) {
       currentAnimator.cancel();
       child.clearAnimation();
     }
     currentState = STATE_SCROLLED_DOWN;
     animateChildTo(
-        child, height, EXIT_ANIMATION_DURATION, AnimationUtils.FAST_OUT_LINEAR_IN_INTERPOLATOR);
+        child,
+        height + additionalHiddenOffsetY,
+        EXIT_ANIMATION_DURATION,
+        AnimationUtils.FAST_OUT_LINEAR_IN_INTERPOLATOR);
   }
 
   private void animateChildTo(V child, int targetY, long duration, TimeInterpolator interpolator) {

lib/java/com/google/android/material/bottomappbar/BottomAppBar.java

@@ -369,9 +369,23 @@ public void setHideOnScroll(boolean hide) {
     hideOnScroll = hide;
   }
 
+  /** Animates the {@link BottomAppBar} so it hides off the screen. */
+  public void performHide() {
+    getBehavior().slideDown(this);
+  }
+
+  /** Animates the {@link BottomAppBar} so it is shown on the screen. */
+  public void performShow() {
+    getBehavior().slideUp(this);
+  }
+
   @Override
   public void setElevation(float elevation) {
     materialShapeDrawable.setElevation(elevation);
+    // Make sure the shadow isn't shown if this view slides down with hideOnScroll.
+    int topShadowHeight =
+        materialShapeDrawable.getShadowRadius() - materialShapeDrawable.getShadowOffsetY();
+    getBehavior().setAdditionalHiddenOffsetY(this, topShadowHeight);
   }
 
   /**
@@ -788,7 +802,7 @@ public void setSubtitle(CharSequence subtitle) {
 
   @NonNull
   @Override
-  public CoordinatorLayout.Behavior<BottomAppBar> getBehavior() {
+  public Behavior getBehavior() {
     if (behavior == null) {
       behavior = new Behavior();
     }

lib/java/com/google/android/material/shape/MaterialShapeDrawable.java

@@ -745,12 +745,10 @@ public void setShadowCompatRotation(int shadowRotation) {
   }
 
   /**
-   * Get the shadow radius rendered by the path.
-   *
-   * @return the shadow radius rendered by the path.
-   * @deprecated use {@link #getElevation()} instead.
+   * Get the shadow radius rendered by the path in pixels. This method should be used only when the
+   * actual size of the shadow is required. Usually {@link getElevation()} should be used instead to
+   * get the actual elevation of this view as it might be different.
    */
-  @Deprecated
   public int getShadowRadius() {
     return drawableState.shadowCompatRadius;
   }
@@ -990,14 +988,8 @@ private void drawStrokeShape(Canvas canvas) {
 
   private void prepareCanvasForShadow(Canvas canvas) {
     // Calculate the translation to offset the canvas for the given offset and rotation.
-    int shadowOffsetX =
-        (int)
-            (drawableState.shadowCompatOffset
-                * Math.sin(Math.toRadians(drawableState.shadowCompatRotation)));
-    int shadowOffsetY =
-        (int)
-            (drawableState.shadowCompatOffset
-                * Math.cos(Math.toRadians(drawableState.shadowCompatRotation)));
+    int shadowOffsetX = getShadowOffsetX();
+    int shadowOffsetY = getShadowOffsetY();
 
     // We only handle clipping as a convenience for older apis where we are trying to seamlessly
     // provide fake shadows. On newer versions of android, we require that the parent is set so that
@@ -1034,20 +1026,28 @@ private void drawCompatShadow(Canvas canvas) {
       edgeShadowOperation[index].draw(shadowRenderer, drawableState.shadowCompatRadius, canvas);
     }
 
-    int shadowOffsetX =
-        (int)
-            (drawableState.shadowCompatOffset
-                * Math.sin(Math.toRadians(drawableState.shadowCompatRotation)));
-    int shadowOffsetY =
-        (int)
-            (drawableState.shadowCompatOffset
-                * Math.cos(Math.toRadians(drawableState.shadowCompatRotation)));
+    int shadowOffsetX = getShadowOffsetX();
+    int shadowOffsetY = getShadowOffsetY();
 
     canvas.translate(-shadowOffsetX, -shadowOffsetY);
     canvas.drawPath(path, clearPaint);
     canvas.translate(shadowOffsetX, shadowOffsetY);
   }
 
+  /** Returns the X offset of the shadow from the bounds of the shape. */
+  public int getShadowOffsetX() {
+    return (int)
+        (drawableState.shadowCompatOffset
+            * Math.sin(Math.toRadians(drawableState.shadowCompatRotation)));
+  }
+
+  /** Returns the Y offset of the shadow from the bounds of the shape. */
+  public int getShadowOffsetY() {
+    return (int)
+        (drawableState.shadowCompatOffset
+            * Math.cos(Math.toRadians(drawableState.shadowCompatRotation)));
+  }
+
   /** @deprecated see {@link ShapeAppearancePathProvider} */
   @Deprecated
   public void getPathForSize(int width, int height, Path path) {

tests/javatests/com/google/android/material/bottomappbar/AndroidManifest.xml

@@ -0,0 +1,32 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  Copyright (C) 2019 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.
+-->
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+  xmlns:tools="http://schemas.android.com/tools"
+  package="com.google.android.material.bottomappbar">
+
+  <uses-sdk
+    tools:overrideLibrary="androidx.test, android.app, androidx.test.rule,
+        androidx.test.espresso, androidx.test.espresso.idling"/>
+
+  <application>
+    <uses-library android:name="android.test.runner"/>
+  </application>
+
+  <instrumentation
+    android:name="androidx.test.runner.AndroidJUnitRunner"
+    android:targetPackage="com.google.android.material.testapp"/>
+</manifest>

tests/javatests/com/google/android/material/bottomappbar/BottomAppBarBehaviorTest.java

@@ -0,0 +1,57 @@
+/*
+ * Copyright (C) 2019 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 com.google.android.material.bottomappbar;
+
+import static org.junit.Assert.assertTrue;
+
+import androidx.appcompat.app.AppCompatActivity;
+import androidx.test.filters.SmallTest;
+import androidx.test.rule.ActivityTestRule;
+import androidx.test.runner.AndroidJUnit4;
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+@SmallTest
+@RunWith(AndroidJUnit4.class)
+public class BottomAppBarBehaviorTest {
+
+  @Rule
+  public final ActivityTestRule<AppCompatActivity> activityTestRule =
+      new ActivityTestRule<>(AppCompatActivity.class);
+
+  BottomAppBar bar;
+
+  @Before
+  public void createBottomAppBar() {
+    bar = new BottomAppBar(activityTestRule.getActivity());
+  }
+
+  @Test
+  public void testMovedDown_elevationIncreasedWhileHidden() throws Throwable {
+    bar.setElevation(10);
+    bar.performHide();
+    float originalYTranslation = bar.getTranslationY();
+
+    bar.setElevation(30);
+
+    assertTrue(
+        "The bar should have bee moved further down to hide the larger shadow.",
+        bar.getTranslationY() > originalYTranslation);
+  }
+}