创建一个名为rounded_corners_shape的形状

<shape xmlns:android="http://schemas.android.com/apk/res/android"
       android:shape="rectangle">
    <corners
        android:topLeftRadius="8dp"
        android:topRightRadius="8dp"/>
    <solid android:color="@color/white"/>

</shape>

定义一个样式

  <style name="AppBottomSheetDialogTheme"
           parent="Theme.Design.Light.BottomSheetDialog">
        <item name="bottomSheetStyle">@style/AppModalStyle</item>
    </style>

    <style name="AppModalStyle" parent="Widget.Design.BottomSheet.Modal">
        <item name="android:background">@drawable/rounded_corners_shape</item>
    </style>

在你的自定义BottomSheetDialogFragment上使用这种风格，它会工作的!

 public class CustomDialogFragment extends BottomSheetDialogFragment {
      @Override
      public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setStyle(STYLE_NORMAL, R.style. AppBottomSheetDialogTheme);
      }

      ...
    }

简单的解决方案:

class TopRoundedCornersFragment : BottomSheetDialogFragment() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        setStyle(STYLE_NORMAL, R.style.AppBottomSheetDialogTheme)
    }
}

在styles.xml

<style name="BottomSheetStyle" parent="Widget.Design.BottomSheet.Modal">
    <item name="android:background">@drawable/bottom_sheet_dialog_bg</item>
</style>

<style name="AppBottomSheetDialogTheme" parent="Theme.Design.Light.BottomSheetDialog">
    <item name="bottomSheetStyle">@style/BottomSheetStyle</item>
</style>

最后，创建一个顶部圆角可绘制资源(bottom_sheet_dialog_bg.xml)

<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">

    <solid android:color="@android:color/white" />
    <corners
        android:topLeftRadius="4dp"
        android:topRightRadius="4dp" />

</shape>

Koma Yip回答的另一个问题对我有用，你应该试试。

在drawable中创建一个xml，比如dialog_bg.xml <？XML版本="1.0"编码="utf-8"?> <形状xmlns: android = " http://schemas.android.com/apk/res/android " > <固体android:颜色= " @color /白色" / > <corners android:半径="30dp" /> <填充 android:左= " 10 dp” android:顶级= " 10 dp” android:对= " 10 dp” android:底部= " 10 dp " / > < / >形状

把这个放在你的布局XML根节点中:

将其设置为布局XML中的背景 android:背景= " @drawable / dialog_bg”

在onCreateView()中放入:

将对话框的背景设置为透明 dialog.getWindow()。setBackgroundDrawable(新ColorDrawable (Color.TRANSPARENT));

完整的解决方案:

将下面的样式属性添加到style.xml。

<style name="AppBottomSheetDialogTheme"
    parent="Theme.Design.Light.BottomSheetDialog">
    <item name="bottomSheetStyle">@style/AppModalStyle</item>
</style>

<style name="AppModalStyle"
    parent="Widget.Design.BottomSheet.Modal">
    <item name="android:background">@drawable/bottom_sheet_background</item>
</style>

然后使用AppBottomSheetDialogTheme从您的代码创建一个底部表对话框。

private fun openBottomSheetTermsCondition() {
    val mBottomSheetDialog = BottomSheetDialog(requireContext(),R.style.AppBottomSheetDialogTheme)
    val sheetView = layoutInflater.inflate(R.layout.bottom_sheet_travel_advice_terms, null)
    mBottomSheetDialog.setContentView(sheetView)
    sheetView.tv_head.setOnClickListener {
        mBottomSheetDialog.dismiss()
    }

    sheetView.webView.loadDataWithBaseURL(null,getString(R.string.privacy_policy_body_html),"text/html", "utf-8", null)
    mBottomSheetDialog.show()
}

我使用下面的绘图来圆底稿背景。

    <?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <corners
        android:topLeftRadius="@dimen/bottom_sheet_corner_radius"
        android:topRightRadius="@dimen/bottom_sheet_corner_radius" />
    <solid android:color="@color/white" />
</shape>

底部表格xml

    <?xml version="1.0" encoding="utf-8"?>
<androidx.cardview.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:behavior_hideable="false"
    app:behavior_peekHeight="@dimen/bottom_sheet_peek_height"
    app:cardCornerRadius="@dimen/spacing_normal"
    app:layout_behavior="com.google.android.material.bottomsheet.BottomSheetBehavior">

    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:paddingBottom="@dimen/spacing_small">

        <androidx.constraintlayout.widget.Guideline
            android:id="@+id/begin_horizontal_guideline"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:orientation="horizontal"
            app:layout_constraintGuide_begin="@dimen/activity_vertical_margin" />

        <androidx.constraintlayout.widget.Guideline
            android:id="@+id/begin_vertical_guideline"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:orientation="vertical"
            app:layout_constraintGuide_begin="@dimen/activity_horizontal_margin" />

        <androidx.constraintlayout.widget.Guideline
            android:id="@+id/end_vertical_guideline"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:orientation="vertical"
            app:layout_constraintGuide_end="@dimen/activity_horizontal_margin" />

        <View
            android:id="@+id/sheet_header_shadow"
            android:layout_width="match_parent"
            android:layout_height="@dimen/spacing_tiny"
            android:layout_marginStart="10dp"
            android:layout_marginEnd="10dp"
            android:background="@drawable/bottom_sheet_header_shadow"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent" />

        <androidx.appcompat.widget.AppCompatTextView
            android:id="@+id/tv_head"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:drawablePadding="@dimen/spacing_normal"
            android:fontFamily="sans-serif-medium"
            android:gravity="start"
            android:padding="@dimen/spacing_small"
            android:text="@string/term_and_condition"
            android:textColor="@color/greyish_brown"
            android:textSize="20sp"
            app:drawableLeftCompat="@drawable/ic_close_black_24dp"
            app:layout_constraintEnd_toEndOf="@id/end_vertical_guideline"
            app:layout_constraintStart_toStartOf="@id/begin_vertical_guideline"
            app:layout_constraintTop_toBottomOf="@+id/begin_horizontal_guideline" />

        <View
            android:id="@+id/line_separation"
            android:layout_width="match_parent"
            android:layout_height="1dp"
            android:layout_marginTop="@dimen/spacing_small"
            android:background="@color/blue_gray"
            app:layout_constraintTop_toBottomOf="@+id/tv_head" />

        <WebView
            android:id="@+id/webView"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            app:layout_constraintEnd_toEndOf="@id/end_vertical_guideline"
            app:layout_constraintStart_toStartOf="@id/begin_vertical_guideline"
            app:layout_constraintTop_toBottomOf="@id/line_separation" />

    </androidx.constraintlayout.widget.ConstraintLayout>

</androidx.cardview.widget.CardView>

底部对话框设置了默认的白色背景色，这就是为什么角落是不可见的，为了显示它们，你需要通过覆盖底部对话框的风格使对话框的背景透明。

在res/values/styles/styles.xml中定义此样式

<style name="BottomSheetDialog" parent="Theme.Design.Light.BottomSheetDialog">
    <item name="bottomSheetStyle">@style/bottomSheetStyleWrapper</item>
</style>

<style name="bottomSheetStyleWrapper" parent="Widget.Design.BottomSheet.Modal">
    <item name="android:background">@android:color/transparent</item>
</style>

并将此样式设置为您的BottomSheetDialog

View view = getLayoutInflater().inflate(R.layout.chooser_bottom_sheet, null);
BottomSheetDialog dialog = new BottomSheetDialog(this,R.style.BottomSheetDialog); // Style here
dialog.setContentView(view);
dialog.show();

我知道这个问题已经有了一个公认的答案。我想要记录我经历的问题，以及我最终是如何让它工作的，这样它对未来的人是有用的。

Firstly, I was using Theme.AppCompat.Light.DarkActionBar as the parent for our AppTheme. This meant @Gabriele Mariotti solution kept crashing with the error Could not inflate Behavior subclass com.google.android.material.bottomsheet.BottomSheetBehavior. I fixed this by simply changing the parent to Theme.MaterialComponents.Light.DarkActionBar. This did not affect our theme in any way but the RTE was gone. You can also fix this issue by simply including the require items to your style. But I didn't bother figuring out which styles were required by BottomSheetBehavior.

其次，尝试我可能，但我不能得到实际的框架布局(这是BottomSheetDialogFragment)使用圆角。我意识到，将此设置为图像Drawable工作，但不适用于形状或@null。事实证明，这是因为我使用的LinearLayout有一个定义的背景。这覆盖了样式中的任何背景。去掉它最终会产生圆角。

此外，我不需要设置任何背景形状来圆角。@Gabriele Mariotti的解决方案在我做出上述更改后立即起作用。然而，为了设置我想要的背景色，我必须覆盖“backgroundTint”项。

PS:我是Android开发的新手，我正在维护一个旧的应用程序，这是我们学院内部使用的。我不是很熟悉Android的布局系统或材料库。我想这就是为什么我花了3天时间才弄明白。我希望这对将来的人有用。