使用新的 Material Component 库，您可以在您的样式中使用 shapeAppearanceOverlay 属性 customize the shape 组件（注意：它至少需要版本1.1.0)
只需使用 BottomSheetDialogFragment 覆盖 onCreateView 方法，然后为底部工作表对话框定义您的自定义样式。
在您的应用主题的styles.xml 中定义bottomSheetDialogTheme 属性：
<!-- Base application theme. -->
<style name="AppTheme" parent="Theme.MaterialComponents.Light">
<!-- Customize your theme here. -->
<item name="colorPrimary">@color/colorPrimary</item>
....
<item name="bottomSheetDialogTheme">@style/CustomBottomSheetDialog</item>
</style>
然后用shapeAppearanceOverlay定义你最喜欢的形状
<style name="CustomBottomSheetDialog" parent="@style/ThemeOverlay.MaterialComponents.BottomSheetDialog">
<item name="bottomSheetStyle">@style/CustomBottomSheet</item>
</style>
<style name="CustomBottomSheet" parent="Widget.MaterialComponents.BottomSheet">
<item name="shapeAppearanceOverlay">@style/CustomShapeAppearanceBottomSheetDialog</item>
</style>
<style name="CustomShapeAppearanceBottomSheetDialog" parent="">
<item name="cornerFamily">rounded</item>
<item name="cornerSizeTopRight">16dp</item>
<item name="cornerSizeTopLeft">16dp</item>
<item name="cornerSizeBottomRight">0dp</item>
<item name="cornerSizeBottomLeft">0dp</item>
</style>
您可以在您的BottomSheetDialogFragment 中获得覆盖此方法的相同行为（而不是在您的应用主题中添加bottomSheetDialogTheme）：
@Override public int getTheme() {
return R.style.CustomBottomSheetDialog;
}
在这种情况下，您仅在单个 BottomSheetDialogFragment 中使用此 themeOverlay，而不是在所有应用中。
关于扩展状态的重要说明：
在展开状态下，BottomSheet 有平角。可以在github repo查看官方评论：
我们的设计团队强烈认为圆角表示可滚动的内容，而平角表示没有额外的内容。因此，他们不希望我们使用 fitToContents 添加此更改。
此行为由BottomSheetBehavior 提供，无法覆盖它。
但是有一个解决方法 -> 免责声明： 它可能会在下一个版本中停止工作！！
您可以在BottomSheetDialogFragment 中添加BottomSheetCallback：
@NonNull @Override public Dialog onCreateDialog(@Nullable Bundle savedInstanceState) {
Dialog dialog = super.onCreateDialog(savedInstanceState);
((BottomSheetDialog)dialog).getBehavior().addBottomSheetCallback(new BottomSheetBehavior.BottomSheetCallback() {
@Override public void onStateChanged(@NonNull View bottomSheet, int newState) {
if (newState == BottomSheetBehavior.STATE_EXPANDED) {
//In the EXPANDED STATE apply a new MaterialShapeDrawable with rounded cornes
MaterialShapeDrawable newMaterialShapeDrawable = createMaterialShapeDrawable(bottomSheet);
ViewCompat.setBackground(bottomSheet, newMaterialShapeDrawable);
}
}
@Override public void onSlide(@NonNull View bottomSheet, float slideOffset) {
}
});
return dialog;
}
@NotNull private MaterialShapeDrawable createMaterialShapeDrawable(@NonNull View bottomSheet) {
ShapeAppearanceModel shapeAppearanceModel =
//Create a ShapeAppearanceModel with the same shapeAppearanceOverlay used in the style
ShapeAppearanceModel.builder(getContext(), 0, R.style.CustomShapeAppearanceBottomSheetDialog)
.build();
//Create a new MaterialShapeDrawable (you can't use the original MaterialShapeDrawable in the BottoSheet)
MaterialShapeDrawable currentMaterialShapeDrawable = (MaterialShapeDrawable) bottomSheet.getBackground();
MaterialShapeDrawable newMaterialShapeDrawable = new MaterialShapeDrawable((shapeAppearanceModel));
//Copy the attributes in the new MaterialShapeDrawable
newMaterialShapeDrawable.initializeElevationOverlay(getContext());
newMaterialShapeDrawable.setFillColor(currentMaterialShapeDrawable.getFillColor());
newMaterialShapeDrawable.setTintList(currentMaterialShapeDrawable.getTintList());
newMaterialShapeDrawable.setElevation(currentMaterialShapeDrawable.getElevation());
newMaterialShapeDrawable.setStrokeWidth(currentMaterialShapeDrawable.getStrokeWidth());
newMaterialShapeDrawable.setStrokeColor(currentMaterialShapeDrawable.getStrokeColor());
return newMaterialShapeDrawable;
}