API to set height of a half expanded sheet, in proportion to parent height

PiperOrigin-RevId: 239689682

Author: melaniegoetz

lib/java/com/google/android/material/bottomsheet/BottomSheetBehavior.java

@@ -195,6 +195,8 @@ public abstract static class BottomSheetCallback {
 
   int halfExpandedOffset;
 
+  float halfExpandedRatio = 0.5f;
+
   int collapsedOffset;
 
   boolean hideable;
@@ -261,6 +263,7 @@ public BottomSheetBehavior(Context context, AttributeSet attrs) {
     setSkipCollapsed(
         a.getBoolean(R.styleable.BottomSheetBehavior_Layout_behavior_skipCollapsed, false));
     setSaveFlags(a.getInt(R.styleable.BottomSheetBehavior_Layout_behavior_saveFlags, SAVE_NONE));
+    setHalfExpandedRatio(a.getFloat(R.styleable.BottomSheetBehavior_Layout_behavior_halfExpandedRatio, 0.5f));
     a.recycle();
     ViewConfiguration configuration = ViewConfiguration.get(context);
     maximumVelocity = configuration.getScaledMaximumFlingVelocity();
@@ -335,7 +338,7 @@ public boolean onLayoutChild(CoordinatorLayout parent, V child, int layoutDirect
     parentWidth = parent.getWidth();
     parentHeight = parent.getHeight();
     fitToContentsOffset = Math.max(0, parentHeight - child.getHeight());
-    halfExpandedOffset = parentHeight / 2;
+    calculateHalfExpandedOffset();
     calculateCollapsedOffset();
 
     if (state == STATE_EXPANDED) {
@@ -692,6 +695,32 @@ public final int getPeekHeight() {
     return peekHeightAuto ? PEEK_HEIGHT_AUTO : peekHeight;
   }
 
+  /**
+   * Determines the height of the BottomSheet in the {@link #STATE_HALF_EXPANDED} state. The
+   * material guidelines recommended a value of 0.5, which results in the sheet filling half of the
+   * parent. The height of the BottomSheet will be smaller as this ratio is decreased and taller as
+   * it is increased. The default value is 0.5.
+   *
+   * @param ratio a float between 0 and 1, representing the {@link #STATE_HALF_EXPANDED} ratio.
+   * @attr com.google.android.material.R.styleable#BottomSheetBehavior_Layout_behavior_halfExpandedRatio
+   */
+  public void setHalfExpandedRatio(float ratio) {
+
+    if ((ratio <= 0) || (ratio >= 1)) {
+      throw new IllegalArgumentException("ratio must be a float value between 0 and 1");
+    }
+    this.halfExpandedRatio = ratio;
+  }
+
+   /**
+   * Gets the ratio for the height of the BottomSheet in the {@link #STATE_HALF_EXPANDED} state.
+   *
+   * @attr com.google.android.material.R.styleable#BottomSheetBehavior_Layout_behavior_halfExpandedRatio
+   */
+  public float getHalfExpandedRatio() {
+    return halfExpandedRatio;
+  }
+
   /**
    * Sets whether this bottom sheet can hide when it is swiped down.
    *
@@ -895,6 +924,10 @@ private void calculateCollapsedOffset() {
     }
   }
 
+  private void calculateHalfExpandedOffset() {
+      this.halfExpandedOffset = (int) (parentHeight * halfExpandedRatio);
+  }
+
   private void reset() {
     activePointerId = ViewDragHelper.INVALID_POINTER;
     if (velocityTracker != null) {

lib/java/com/google/android/material/bottomsheet/res/values/attrs.xml

@@ -33,6 +33,11 @@
     <attr name="behavior_skipCollapsed" format="boolean"/>
     <!-- Whether height of expanded sheet wraps content or not -->
     <attr name="behavior_fitToContents" format="boolean"/>
+    <!-- The ratio to be used to set the height of half-expanded state in proportion to parent, when
+         fitToContents is false. Defaults to true half, 0.5, if not explicitly set. Ratio must be a
+         float value between 0 and 1 and produce a half-expanded state height larger than the
+         peek height for the half-expanded state to be operational -->
+    <attr name="behavior_halfExpandedRatio" format="reference|float"/>
     <!-- Shape appearance style reference for BottomSheet. Attribute declaration is in the shape
          package. -->
      <attr name="shapeAppearance"/>