鸿蒙系统上悬浮窗里的Toast在应用程序外部不响应

a.md

权限：

<uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW"/>

长按按钮先同意悬浮窗权限，然后点击它，会出现一个通过WindowManager创建的悬浮按钮。悬浮按钮点击的时候会有Toast信息，但是到应用外部，比如说返回到桌面，再点悬浮按钮，Toast不显示。

MainActivity.kt

package com.example.test

import android.content.Context
import android.content.Intent
import android.graphics.PixelFormat
import android.net.Uri
import android.os.Bundle
import android.provider.Settings
import android.view.WindowManager
import android.view.WindowManager.LayoutParams.*
import android.widget.Button
import android.widget.Toast
import androidx.activity.result.contract.ActivityResultContract
import androidx.appcompat.app.AppCompatActivity

class OverlaySettingContract : ActivityResultContract<String, Unit>() {
    override fun createIntent(context: Context, input: String): Intent {
        return Intent(Settings.ACTION_MANAGE_OVERLAY_PERMISSION, Uri.parse("package:$input"))
    }

    override fun parseResult(resultCode: Int, intent: Intent?) {
    }
}

class MainActivity : AppCompatActivity() {
    private val overlaySettingLauncher = registerForActivityResult(OverlaySettingContract()) {}

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

        setContentView(R.layout.activity_main)

        val button = findViewById<Button>(R.id.button)
        button.setOnClickListener {
            createFloatingWindow()
        }
        button.setOnLongClickListener {
            overlaySettingLauncher.launch(this.packageName)
            return@setOnLongClickListener true
        }
    }

    private fun createFloatingWindow() {
        val wm = applicationContext.getSystemService(WindowManager::class.java)!!
        val lp = WindowManager.LayoutParams()
        lp.apply {
            type = TYPE_APPLICATION_OVERLAY
            format = PixelFormat.RGBA_8888
            flags = FLAG_NOT_FOCUSABLE
            width = WRAP_CONTENT
            height = WRAP_CONTENT
        }

        val button = Button(this)
        wm.addView(button, lp)

        button.setOnClickListener {
            /*val handler = Handler(Looper.getMainLooper())
            handler.post {
                Toast.makeText(this, "Test", Toast.LENGTH_SHORT).show()
            }*/
            Toast.makeText(this, "Test", Toast.LENGTH_SHORT).show()
        }
    }
}