在Kotlin中，你可以使用以下代码:

val dialog = Dialog(context)
dialog.window?.decorView?.background = null

如果你使用Kotlin，这段代码可以帮助你:

Objects.requireNonNull(dialog.window)
                ?.setBackgroundDrawable(ColorDrawable(Color.TRANSPARENT))

这就是我用AlertDialog实现半透明的方法。

创建自定义样式:

<style name="TranslucentDialog" parent="@android:style/Theme.DeviceDefault.Dialog.Alert">
    <item name="android:colorBackground">#32FFFFFF</item>
</style>

然后创建对话框:

AlertDialog.Builder builder = new AlertDialog.Builder(getActivity(), R.style.TranslucentDialog);
AlertDialog dialog = builder.create();

Kotlin创建透明背景对话框的方法:

 Dialog(activity!!, R.style.LoadingIndicatorDialogStyle)
            .apply {
                // requestWindowFeature(Window.FEATURE_NO_TITLE)
                setCancelable(true)
                setContentView(R.layout.define_your_custom_view_id_here)

                //access your custom view buttons/editText like below.z
                val createBt = findViewById<TextView>(R.id.clipboard_create_project)
                val cancelBt = findViewById<TextView>(R.id.clipboard_cancel_project)
                val clipboard_et = findViewById<TextView>(R.id.clipboard_et)
                val manualOption =
                    findViewById<TextView>(R.id.clipboard_manual_add_project_option)

                //if you want to perform any operation on the button do like this

                createBt.setOnClickListener {
                    //handle your button click here
                    val enteredData = clipboard_et.text.toString()
                    if (enteredData.isEmpty()) {
                        Utils.toast("Enter project details")
                    } else {
                        navigateToAddProject(enteredData, true)
                        dismiss()
                    }
                }

                cancelBt.setOnClickListener {
                    dismiss()
                }
                manualOption.setOnClickListener {
                    navigateToAddProject("", false)
                    dismiss()
                }
                show()
            }

在style.xml中创建LoadingIndicatorDialogStyle，如下所示:

<style name="LoadingIndicatorDialogStyle" parent="Theme.AppCompat.Light.Dialog.Alert">
    <item name="android:windowIsTranslucent">true</item>
    <item name="android:windowBackground">@android:color/transparent</item>
    <item name="android:windowContentOverlay">@null</item>
    <item name="android:windowNoTitle">true</item>
    <item name="android:statusBarColor">@color/black_transperant</item>
    <item name="android:layout_gravity">center</item>
    <item name="android:background">@android:color/transparent</item>
    <!--<item name="android:windowAnimationStyle">@style/MaterialDialogSheetAnimation</item>-->
</style>

不知何故，撒迦利亚的解决方案对我不起作用，所以我用下面的主题来解决这个问题…

<style name="DialogCustomTheme" parent="android:Theme.Holo.Dialog.NoActionBar">
    <item name="android:windowBackground">@android:color/transparent</item>
    <item name="android:colorBackgroundCacheHint">@null</item>
</style>

可以将此主题设置为对话框，如下所示

final Dialog dialog = new Dialog(this, R.style.DialogCustomTheme); 

享受! !

你可以使用:

setBackgroundDrawable(null);

方法。下面是文档:

  /**
    * Set the background to a given Drawable, or remove the background. If the
    * background has padding, this View's padding is set to the background's
    * padding. However, when a background is removed, this View's padding isn't
    * touched. If setting the padding is desired, please use
    * {@link #setPadding(int, int, int, int)}.
    *
    * @param d The Drawable to use as the background, or null to remove the
    *        background
    */