[Adaptive] [Side Sheets] Add SideSheetCallback listener to SideSheetBehavior to track @SheetState state change events.

Includes a fix for a really strange issue where setting the background color from the callback worked, but if setText was called, it would cause the sheet to flash off the screen when STATE_EXPANDED was reached.

PiperOrigin-RevId: 493409073
(cherry picked from commit 2468d6c)

Author: afohrman

lib/java/com/google/android/material/sidesheet/RightSheetDelegate.java

@@ -198,4 +198,12 @@ boolean isSettling(View child, int state, boolean isReleasingView) {
   <V extends View> int getOutwardEdge(@NonNull V child) {
     return child.getLeft();
   }
+
+  @Override
+  float calculateSlideOffsetBasedOnOutwardEdge(int left) {
+    float hiddenOffset = getHiddenOffset();
+    float sheetWidth = hiddenOffset - getExpandedOffset();
+
+    return (hiddenOffset - left) / sheetWidth;
+  }
 }

lib/java/com/google/android/material/sidesheet/SheetDelegate.java

@@ -93,4 +93,13 @@ abstract <V extends View> void setTargetStateOnNestedPreScroll(
    * this would return {@code child.getLeft()}.
    */
   abstract <V extends View> int getOutwardEdge(@NonNull V child);
+
+  /**
+   * Returns the calculated slide offset based on which edge of the screen the sheet is based on.
+   * The offset value increases as the sheet moves towards the outward edge.
+   *
+   * @return slide offset represented as a float value between 0 and 1. A value of 0 means that the
+   *     sheet is hidden and a value of 1 means that the sheet is fully expanded.
+   */
+  abstract float calculateSlideOffsetBasedOnOutwardEdge(int outwardEdge);
 }

lib/java/com/google/android/material/sidesheet/SideSheetBehavior.java

@@ -52,12 +52,15 @@
 import androidx.core.view.accessibility.AccessibilityViewCommand;
 import androidx.customview.view.AbsSavedState;
 import androidx.customview.widget.ViewDragHelper;
+import com.google.android.material.internal.ViewUtils;
 import com.google.android.material.resources.MaterialResources;
 import com.google.android.material.shape.MaterialShapeDrawable;
 import com.google.android.material.shape.ShapeAppearanceModel;
 import java.lang.ref.WeakReference;
 import java.util.HashMap;
+import java.util.LinkedHashSet;
 import java.util.Map;
+import java.util.Set;
 
 /**
  * An interaction behavior plugin for a child view of {@link CoordinatorLayout} to make it work as a
@@ -123,6 +126,8 @@ public class SideSheetBehavior<V extends View> extends CoordinatorLayout.Behavio
   private int initialX;
   private int initialY;
 
+  @NonNull private final Set<SideSheetCallback> callbacks = new LinkedHashSet<>();
+
   private boolean touchingScrollingChild;
 
   @Nullable private Map<View, Integer> importantForAccessibilityMap;
@@ -319,6 +324,11 @@ public boolean onLayoutChild(
     ViewCompat.offsetLeftAndRight(child, currentOffset);
 
     nestedScrollingChildRef = new WeakReference<>(findScrollingChild(child));
+
+    for (SideSheetCallback callback : callbacks) {
+      callback.onLayout(child);
+    }
+
     return true;
   }
 
@@ -335,7 +345,11 @@ private int calculateCurrentOffset(int savedOutwardEdge, V child) {
 
     switch (state) {
       case STATE_EXPANDED:
-        currentOffset = savedOutwardEdge;
+        // TODO (b/261619910): This is a workaround for a bug where the expanded offset was getting
+        // recalculated if onLayoutChild() was called while the sheet was in the process of
+        // expanding/offsetting. Revisit this and refactor if necessary when adding left based
+        // sheets.
+        currentOffset = ViewUtils.isLayoutRtl(child) ? getExpandedOffset() : 0;
         break;
       case STATE_DRAGGING:
       case STATE_SETTLING:
@@ -494,6 +508,7 @@ public void onNestedPreScroll(
     }
     sheetDelegate.setTargetStateOnNestedPreScroll(
         coordinatorLayout, child, target, dx, dy, consumed, type);
+    dispatchOnSlide(child, sheetDelegate.getOutwardEdge(child));
     lastNestedScrollDx = dx;
     nestedScrolled = true;
   }
@@ -601,6 +616,24 @@ float getHideThreshold() {
     return HIDE_THRESHOLD;
   }
 
+  /**
+   * Adds a callback to be notified of side sheet events.
+   *
+   * @param callback The callback to notify when side sheet events occur.
+   */
+  public void addCallback(@NonNull SideSheetCallback callback) {
+    callbacks.add(callback);
+  }
+
+  /**
+   * Removes a previously added callback.
+   *
+   * @param callback The callback to remove.
+   */
+  public void removeCallback(@NonNull SideSheetCallback callback) {
+    callbacks.remove(callback);
+  }
+
   /**
    * Sets the state of the sheet. The sheet will transition to that state with animation.
    *
@@ -679,6 +712,10 @@ void setStateInternal(@SheetState int state) {
       updateImportantForAccessibility(false);
     }
 
+    for (SideSheetCallback callback : callbacks) {
+      callback.onStateChanged(sheet, state);
+    }
+
     updateAccessibilityActions();
   }
 
@@ -794,6 +831,12 @@ public boolean tryCaptureView(@NonNull View child, int pointerId) {
           return viewRef != null && viewRef.get() == child;
         }
 
+        @Override
+        public void onViewPositionChanged(
+            @NonNull View changedView, int left, int top, int dx, int dy) {
+          dispatchOnSlide(changedView, left);
+        }
+
         @Override
         public void onViewDragStateChanged(@SheetState int state) {
           if (state == ViewDragHelper.STATE_DRAGGING && draggable) {
@@ -825,6 +868,15 @@ public int getViewHorizontalDragRange(@NonNull View child) {
         }
       };
 
+  private void dispatchOnSlide(@NonNull View child, int outwardEdge) {
+    if (!callbacks.isEmpty()) {
+      float slideOffset = sheetDelegate.calculateSlideOffsetBasedOnOutwardEdge(outwardEdge);
+      for (SideSheetCallback callback : callbacks) {
+        callback.onSlide(child, slideOffset);
+      }
+    }
+  }
+
   /**
    * Checks whether a nested scroll should be enabled. If {@code false} all nested scrolls will be
    * consumed by the side sheet.

lib/java/com/google/android/material/sidesheet/SideSheetCallback.java

@@ -0,0 +1,47 @@
+/*
+ * Copyright (C) 2022 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.sidesheet;
+
+import android.view.View;
+import androidx.annotation.NonNull;
+import com.google.android.material.sidesheet.Sheet.SheetState;
+
+/** Callback that monitors side sheet events. */
+public abstract class SideSheetCallback {
+
+  /**
+   * Called when the sheet changes its state.
+   *
+   * @param sheet The sheet view.
+   * @param newState The new state. This should be one of {@link SideSheetBehavior#STATE_DRAGGING},
+   *     {@link SideSheetBehavior#STATE_SETTLING}, {@link SideSheetBehavior#STATE_EXPANDED} or
+   *     {@link SideSheetBehavior#STATE_HIDDEN}.
+   */
+  public abstract void onStateChanged(@NonNull View sheet, @SheetState int newState);
+
+  /**
+   * Called when the sheet is being dragged.
+   *
+   * @param sheet The sheet view.
+   * @param slideOffset The new offset of this sheet within [0,1] range. Offset increases as this
+   *     sheet is moving towards the outward edge. A value of 0 means that the sheet is hidden, and
+   *     a value of 1 means that the sheet is fully expanded.
+   */
+  public abstract void onSlide(@NonNull View sheet, float slideOffset);
+
+  void onLayout(@NonNull View sheet) {}
+}

lib/javatests/com/google/android/material/sidesheet/SideSheetCallbackTest.java

@@ -0,0 +1,121 @@
+/*
+ * Copyright (C) 2022 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.sidesheet;
+
+import com.google.android.material.test.R;
+
+import static android.graphics.Color.RED;
+import static com.google.common.truth.Truth.assertThat;
+import static org.robolectric.Shadows.shadowOf;
+
+import android.graphics.drawable.ColorDrawable;
+import android.os.Bundle;
+import android.os.Looper;
+import androidx.appcompat.app.AppCompatActivity;
+import android.view.View;
+import androidx.annotation.NonNull;
+import androidx.coordinatorlayout.widget.CoordinatorLayout;
+import androidx.core.view.ViewCompat;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.robolectric.Robolectric;
+import org.robolectric.RobolectricTestRunner;
+
+/** Tests for {@link com.google.android.material.sidesheet.SideSheetBehavior}. */
+@RunWith(RobolectricTestRunner.class)
+public class SideSheetCallbackTest {
+
+  private View sideSheet;
+  private SideSheetBehavior<View> sideSheetBehavior;
+
+  @Before
+  public void setUp() throws Exception {
+    AppCompatActivity activity = Robolectric.buildActivity(TestActivity.class).setup().get();
+    CoordinatorLayout coordinatorLayout =
+        (CoordinatorLayout) activity.getLayoutInflater().inflate(R.layout.test_side_sheet, null);
+    sideSheet = coordinatorLayout.findViewById(R.id.test_side_sheet_container);
+    sideSheetBehavior = SideSheetBehavior.from(sideSheet);
+
+    activity.setContentView(coordinatorLayout);
+
+    // Wait until the layout is measured.
+    shadowOf(Looper.getMainLooper()).idle();
+  }
+
+  @Test
+  public void test_setSheetRedOnExpandWithCallback_sheetIsRedOnExpand() {
+    // Create a callback and add it to the side sheet behavior.
+    sideSheetBehavior.addCallback(
+        new SideSheetCallback() {
+          @Override
+          public void onStateChanged(@NonNull View sheet, int newState) {
+            if (newState == SideSheetBehavior.STATE_EXPANDED) {
+              ViewCompat.setBackground(sideSheet, new ColorDrawable(RED));
+            }
+          }
+
+          @Override
+          public void onSlide(@NonNull View sheet, float slideOffset) {}
+        });
+
+    sideSheetBehavior.expand();
+    shadowOf(Looper.getMainLooper()).idle();
+
+    assertThat(sideSheetBehavior.getState()).isEqualTo(SideSheetBehavior.STATE_EXPANDED);
+    assertThat(sideSheet.getBackground()).isInstanceOf(ColorDrawable.class);
+    assertThat(((ColorDrawable) sideSheet.getBackground()).getColor()).isEqualTo(RED);
+  }
+
+  @Test
+  public void test_removeCallback_callbackIsRemoved() {
+    SideSheetCallback sideSheetCallback = createExpandedRedSideSheetCallback();
+    // Ensure that side sheet doesn't already have a background.
+    ViewCompat.setBackground(sideSheet, null);
+
+    sideSheetBehavior.addCallback(sideSheetCallback);
+    sideSheetBehavior.removeCallback(sideSheetCallback);
+
+    sideSheetBehavior.expand();
+    shadowOf(Looper.getMainLooper()).idle();
+
+    assertThat(sideSheetBehavior.getState()).isEqualTo(SideSheetBehavior.STATE_EXPANDED);
+    assertThat(sideSheet.getBackground()).isNull();
+  }
+
+  private SideSheetCallback createExpandedRedSideSheetCallback() {
+    return new SideSheetCallback() {
+      @Override
+      public void onStateChanged(@NonNull View sheet, int newState) {
+        if (newState == SideSheetBehavior.STATE_EXPANDED) {
+          ViewCompat.setBackground(sideSheet, new ColorDrawable(RED));
+        }
+      }
+
+      @Override
+      public void onSlide(@NonNull View sheet, float slideOffset) {}
+    };
+  }
+
+  private static class TestActivity extends AppCompatActivity {
+    @Override
+    protected void onCreate(Bundle bundle) {
+      super.onCreate(bundle);
+      setTheme(R.style.Theme_Material3_Light_NoActionBar);
+    }
+  }
+}

lib/javatests/com/google/android/material/sidesheet/res/layout/test_side_sheet.xml

@@ -0,0 +1,39 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  Copyright 2022 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.
+  -->
+<androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
+  xmlns:app="http://schemas.android.com/apk/res-auto"
+  xmlns:tools="http://schemas.android.com/tools"
+  android:id="@+id/test_coordinator_layout"
+  android:layout_width="match_parent"
+  android:layout_height="match_parent"
+  android:fitsSystemWindows="true">
+
+  <LinearLayout
+    android:id="@+id/test_side_sheet_container"
+    style="@style/Widget.Material3.SideSheet"
+    android:layout_width="256dp"
+    android:layout_height="match_parent"
+    android:orientation="vertical"
+    app:layout_behavior="@string/side_sheet_behavior"
+    tools:targetApi="lollipop">
+    <TextView
+      android:layout_width="wrap_content"
+      android:layout_height="match_parent"
+      android:text="Test Side Sheet Content" />
+  </LinearLayout>
+
+</androidx.coordinatorlayout.widget.CoordinatorLayout>