使用新的Material Component库，您可以使用样式中的属性来自定义组件的形状shapeAppearanceOverlay（注意：它需要版本1.1.0）
只需使用BottomSheetDialogFragment覆盖onCreateView方法，然后为“底表对话框”定义自定义样式。
在您的应用主题中定义bottomSheetDialogTheme属性styles.xml：
<style name="AppTheme" parent="Theme.MaterialComponents.Light">
<item name="colorPrimary">@color/colorPrimary</item>
....
<item name="bottomSheetDialogTheme">@style/CustomBottomSheetDialog</item>
</style>
然后只需定义您喜欢的形状 shapeAppearanceOverlay
<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>
您可以在您的应用程序中获得相同的行为来替代此方法BottomSheetDialogFragment（而不是bottomSheetDialogTheme在应用程序主题中添加）：
@Override public int getTheme() {
return R.style.CustomBottomSheetDialog;
}
在这种情况下，您仅在单个BottomSheetDialogFragment应用程序中而不是在所有应用程序中都使用此themeOverlay 。
关于扩展状态的重要说明：
在扩展状态下，BottomSheet具有平角。您可以在github repo中查看官方评论：
我们的设计团队强烈认为，圆角表示可滚动的内容，而平角表示没有其他内容。因此，他们不希望我们使用fitToContents添加此更改。
此行为由提供，BottomSheetBehavior并且无法覆盖它。
但是，有一种解决方法->免责声明：它可能会在下一版本中停止工作！
您可以添加BottomSheetCallback在BottomSheetDialogFragment：
@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) {
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 =
ShapeAppearanceModel.builder(getContext(), 0, R.style.CustomShapeAppearanceBottomSheetDialog)
.build();
MaterialShapeDrawable currentMaterialShapeDrawable = (MaterialShapeDrawable) bottomSheet.getBackground();
MaterialShapeDrawable newMaterialShapeDrawable = new MaterialShapeDrawable((shapeAppearanceModel));
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;
}