[Docs][BottomSheet] Add more information to BottomSheetDialogFragment docs

PiperOrigin-RevId: 686706770

Author: imhappi

catalog/java/io/material/catalog/bottomsheet/BottomSheetScrollableContentDemoFragment.java

@@ -23,11 +23,11 @@
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
+import android.widget.FrameLayout;
 import androidx.annotation.LayoutRes;
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.core.view.WindowInsetsCompat;
-import com.google.android.material.bottomsheet.BottomSheetBehavior;
 import com.google.android.material.bottomsheet.BottomSheetDialog;
 import com.google.android.material.bottomsheet.BottomSheetDialogFragment;
 import com.google.android.material.internal.ViewUtils;
@@ -56,6 +56,7 @@ protected int getDemoContent() {
   /** A custom bottom sheet dialog fragment. */
   @SuppressWarnings("RestrictTo")
   public static class BottomSheet extends BottomSheetDialogFragment {
+
     @NonNull
     @Override
     public Dialog onCreateDialog(@Nullable Bundle savedInstanceState) {
@@ -64,11 +65,13 @@ public Dialog onCreateDialog(@Nullable Bundle savedInstanceState) {
           new BottomSheetDialog(
               getContext(), R.style.ThemeOverlay_Catalog_BottomSheetDialog_Scrollable);
       new WindowPreferencesManager(requireContext()).applyEdgeToEdgePreference(bottomSheetDialog.getWindow());
-      bottomSheetDialog.setContentView(R.layout.cat_bottomsheet_scrollable_content);
-      View bottomSheetInternal = bottomSheetDialog.findViewById(R.id.design_bottom_sheet);
-      BottomSheetBehavior.from(bottomSheetInternal).setPeekHeight(400);
+      View content =
+          LayoutInflater.from(getContext())
+              .inflate(R.layout.cat_bottomsheet_scrollable_content, new FrameLayout(getContext()));
+      bottomSheetDialog.setContentView(content);
+      bottomSheetDialog.getBehavior().setPeekHeight(400);
 
-      View bottomSheetContent = bottomSheetInternal.findViewById(R.id.bottom_drawer_2);
+      View bottomSheetContent = content.findViewById(R.id.bottom_drawer_2);
       ViewUtils.doOnApplyWindowInsets(bottomSheetContent, (v, insets, initialPadding) -> {
         // Add the inset in the inner NestedScrollView instead to make the edge-to-edge behavior
         // consistent - i.e., the extra padding will only show at the bottom of all content, i.e.,

docs/components/BottomSheet.md

@@ -405,6 +405,33 @@ you need to use `Activity.getSupportFragmentManager()`.
 `BottomSheetDialogFragment`. You can override
 `onCancel(DialogInterface)` or `onDismiss(DialogInterface)` if necessary.
 
+`BottomSheetDialogFragment` wraps the view in a `BottomSheetDialog`, which has
+its own `BottomSheetBehavior`. You can define your own `BottomSheetBehavior`
+through overriding `onCreateDialog`. Note that if overriding `onCreateDialog`,
+you should not override `onCreateView`.
+
+```kt
+
+import android.view.View
+import com.google.android.material.bottomsheet.BottomSheetBehavior
+
+class ModalBottomSheet : BottomSheetDialogFragment() {
+
+  override fun onCreateDialog(
+    savedInstanceState: Bundle?,
+  ): Dialog {
+    val bottomSheetDialog: BottomSheetDialog =
+      BottomSheetDialog(
+        getContext(), R.style.ThemeOverlay_Catalog_BottomSheetDialog_Scrollable
+      )
+    bottomSheetDialog.setContentView(R.layout.bottom_sheet_content)
+    // Set behavior attributes
+    bottomSheetDialog.getBehavior().setPeekHeight(123)
+    return bottomSheetDialog
+  }
+}
+```
+
 ## Anatomy and key properties
 
 Bottom sheets have a sheet, a drag handle, and, if modal, a scrim.