android - 如何为 Spinner DropDown 设置圆角？

Question

我需要自定义微调器 DropDown。它应该是圆角。
现在看起来像这样:
Closed
Open
这个solution不起作用。
布局:

    <androidx.appcompat.widget.AppCompatSpinner
    android:id="@+id/messageSubject"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:textAppearance="@style/Text.Default.Normal"
    android:background="@color/transparent"
    android:minHeight="@dimen/grid_6_25"
    android:layout_marginTop="@dimen/grid_1_75"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/supportQuestion" />

分段:

class SupportFragment : Fragment(R.layout.fragment_support) {

private val viewBinding by viewBinding<FragmentSupportBinding>()

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)
    initView()
}

private fun initView() {
    val adapter = ArrayAdapter.createFromResource(
        requireContext(),
        R.array.message_subject,
        R.layout.spinner_selected
    ).also { adapter ->
        adapter.setDropDownViewResource(R.layout.spinner_dropdown)
    }

    viewBinding.messageSubject.adapter = NothingSelectedSpinnerAdapter(requireContext(), adapter, R.layout.spinner_hint)
}

companion object {
    fun newInstance() = SupportFragment()
}

}

Answer 1

创建圆形背景 spinnerbg.xml

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">
<solid android:color="#3B3B3B" />
<corners android:radius="@dimen/_4sdp" />
</shape>

将其添加到样式。

<style name="SpinnerTheme" parent="android:Widget.Material.Spinner.Underlined">
 <item name="android:background">@drawable/spinnerbg
 </item>
 <item name="android:popupBackground">@drawable/spinnerbg
 </item>

 <item name="android:textAlignment">textStart</item>
</style>

使用样式

<androidx.appcompat.widget.AppCompatSpinner
android:id="@+id/spinner_season"
style="@style/SpinnerTheme"
android:layout_width="@dimen/_100sdp"
android:layout_height="@dimen/_30sdp"
android:layout_alignParentEnd="true"
android:layout_gravity="end"
android:layout_marginEnd="@dimen/_10sdp"
android:spinnerMode="dropdown" />

如果需要，在 java 文件中添加自定义布局。

    ArrayAdapter aa = new ArrayAdapter(context, R.layout.item_spinner, R.id.textview, season1);
    aa.setDropDownViewResource(R.layout.item_spinner_dropdown);