你必须改变底部的主题，以实现顶部圆形布局

创建一个自定义绘制background_bottom_sheet_dialog_fragment.xml:

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
   android:shape="rectangle">
    <corners
       android:topLeftRadius="8dp"
        android:topRightRadius="8dp" />
    <padding android:top="0dp" />
    <solid android:color="@color/white" />
</shape>

然后在styles.xml上使用drawable作为背景覆盖bottomSheetDialogTheme:

<!--Bottom sheet-->
<style name="BottomSheet" parent="@style/Widget.Design.BottomSheet.Modal">
    <item 
    name="android:background">@drawable/background_bottom_sheet_dialog_fragment
    </item>
</style>

<style name="BaseBottomSheetDialog" 
    parent="@style/Theme.Design.Light.BottomSheetDialog">
    <item name="android:windowIsFloating">false</item>
    <item name="bottomSheetStyle">@style/BottomSheet</item>
</style>

<style name="BottomSheetDialogTheme" parent="BaseBottomSheetDialog" />

这将改变你的底页的背景布局

BottomSheetDialog

class SheetFragment() : BottomSheetDialogFragment() {

    lateinit var binding: SheetFragmentBinding;

  override fun onCreateDialog(savedInstanceState: Bundle?): Dialog {
    val dialog = super.onCreateDialog(savedInstanceState) as BottomSheetDialog;
    val view = View.inflate(context, R.layout.fragment_bottom_sheet, null);

    binding = DataBindingUtil.bind(view)!!;
    binding.viewModel = SheetFragmentVM();

    dialog.setContentView(view);

    var bottomSheetBehavior = BottomSheetBehavior.from(view.parent as View);
    bottomSheetBehavior.setPeekHeight(BottomSheetBehavior.PEEK_HEIGHT_AUTO);

    bottomSheetBehavior.setBottomSheetCallback(object : 
     BottomSheetBehavior.BottomSheetCallback() {
        override fun onStateChanged(bottomSheet: View, newState: Int) {
            if (BottomSheetBehavior.STATE_EXPANDED == newState) {
               // do on STATE_EXPANDED
            }
            if (BottomSheetBehavior.STATE_COLLAPSED == newState) {
                // do on STATE_COLLAPSED
            }

            if (BottomSheetBehavior.STATE_HIDDEN == newState) {
                dismiss()

            }
        }

        override fun onSlide(bottomSheet: View, slideOffset: Float) {
           // do on slide
        }
    })

    return dialog
}

我今天也检查了同样的事情，是的，你是对的，下面的代码

this.getDialog().getWindow().setBackgroundDrawableResource(R.drawable.charge_layout_background);

这适用于片段背景，所以相反，你应该从对话框窗口获得底部表视图，并改变背景，这里是代码

 @SuppressLint("RestrictedApi")
    @Override
    public void setupDialog(Dialog dialog, int style) {
        super.setupDialog(dialog, style);
        View rootView = getActivity().getLayoutInflater().inflate(R.layout.view_member_info,null,false);
        unbinder = ButterKnife.bind(this, rootView);
        adjustUIComponents();
        dialog.setContentView(rootView);
        FrameLayout bottomSheet = (FrameLayout) dialog.getWindow().findViewById(android.support.design.R.id.design_bottom_sheet);
        bottomSheet.setBackgroundResource(R.drawable.container_background);
    }

这里的底部是你想要改变的实际视图。

创建一个自定义绘制的rounded_dialog.xml:

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <solid android:color="@android:color/white"/>
    <corners android:topLeftRadius="16dp"
        android:topRightRadius="16dp"/>

</shape>

然后在styles.xml上使用drawable作为背景覆盖bottomSheetDialogTheme:

<style name="AppTheme" parent="Theme.AppCompat.Light.NoActionBar">       
    <item name="bottomSheetDialogTheme">@style/AppBottomSheetDialogTheme</item>
</style>

<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_dialog</item>
</style>

这将改变你的应用程序的所有底部对话框。

这对我很管用。

创建一个背景绘图(例如命名为shape_rounded_dialog):

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

    <solid android:color="@color/color_white" />
    <corners android:topLeftRadius="16dp"
             android:topRightRadius="16dp" />
</shape>

添加下面的样式:

<style name="AppBottomSheetDialogTheme" 
       parent="Theme.MaterialComponents.Light.BottomSheetDialog">

    <item name="bottomSheetStyle">@style/CustomBottomSheetStyle</item>
</style>

<style name="CustomBottomSheetStyle" 
       parent="Widget.Design.BottomSheet.Modal">

    <item name="android:background">@drawable/shape_rounded_dialog</item>
</style>

在你的DialogFragment中，重写getTheme()方法来返回你的样式。

@Override
public int getTheme() {
    return R.style.AppBottomSheetDialogTheme;
}

首先，你应该创建一个可绘制的XML文件，其中包含一个顶部圆角的形状，任何你想要的名称。 我将其命名为bottom rounded_top_shape.xml

<shape
xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle"
>
<solid android:color="@android:color/white" />
<corners
    android:topLeftRadius="16dp"
    android:topRightRadius="16dp"
    />

然后在style.xml中添加这个

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

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

然后在你的应用主题中添加如下所示的行

 <style name="MyAppTheme" parent="Theme.MaterialComponents.Light.Bridge">
    <!-- this line -->
    <item name="bottomSheetDialogTheme">@style/AppBottomSheetDialogTheme</item>
</style>

正如在其他答案中指出的，当state为BottomSheetBehavior时。STATE_EXPANDED角将被压平。

你可以通过设置BottomSheetBehavior的peekHeight属性并使用自定义样式来克服这个问题。

abstract class BaseBottomSheetFragment : BottomSheetDialogFragment(){

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    
        if (state == BottomSheetBehavior.STATE_EXPANDED) {
            val displayMetrics = DisplayMetrics()
            requireActivity().windowManager!!.defaultDisplay!!.getMetrics(displayMetrics)
            (dialog as BottomSheetDialog).behavior.peekHeight = displayMetrics.heightPixels
        } else {
            (dialog as BottomSheetDialog).behavior.state = state
        }
    }

    override fun getTheme(): Int {
        return R.style.CustomBottomSheetDialog
    }
}

CustomBottomSheetDialog风格

<style name="CustomBottomSheetDialog" parent="@style/ThemeOverlay.MaterialComponents.BottomSheetDialog">
    <item name="bottomSheetStyle">@style/CustomBottomSheet</item>
    <item name="materialButtonStyle">@style/CustomMaterialButtonStyle</item>
</style>

<style name="CustomMaterialButtonStyle" parent="@style/Widget.MaterialComponents.Button">
    <item name="cornerRadius">@dimen/dialog_bottom_radius</item>
</style>

<style name="CustomBottomSheet" parent="Widget.MaterialComponents.BottomSheet">
    <item name="shapeAppearanceOverlay">@style/CustomShapeAppearanceBottomSheetDialog</item>
</style>

<style name="CustomShapeAppearanceBottomSheetDialog" parent="">
    <item name="android:background">@android:color/transparent</item>
    <item name="backgroundTint">@android:color/transparent</item>
    <item name="cornerFamily">rounded</item>
    <item name="cornerSizeTopRight">@dimen/dialog_bottom_radius</item>
    <item name="cornerSizeTopLeft">@dimen/dialog_bottom_radius</item>
    <item name="cornerSizeBottomRight">0dp</item>
    <item name="cornerSizeBottomLeft">0dp</item>
</style>