windowManager.addView(view, layoutParams)

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

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content">
 
    <ImageView
        android:layout_width="200dp"
        android:layout_height="100dp"
        android:src="@drawable/huge"></ImageView>
 
    <ImageView
        android:id="@+id/close"
        android:src="@drawable/close"
        android:layout_width="30dp"
        android:layout_height="30dp"
        android:layout_marginLeft="170dp">
 
    </ImageView>
 
</FrameLayout>

package com.example.floatingwindow
 
import android.annotation.SuppressLint
import android.app.Service
import android.content.Context
import android.content.Intent
import android.os.Build
import android.os.IBinder
import android.view.*
import android.widget.ImageView
import android.widget.Toast
 
 
class FloatingWindowService : Service(){
 
    private lateinit var layoutParams: WindowManager.LayoutParams
    private lateinit var windowManager: WindowManager
 
    override fun onBind(intent: Intent): IBinder? {
        // TODO: Return the communication channel to the service.
        throw UnsupportedOperationException("Not yet implemented")
    }
 
    override fun onStartCommand(intent: Intent, flags: Int, startId: Int): Int {
        showFloatingWindow()
        return super.onStartCommand(intent, flags, startId)
    }
 
    @SuppressLint("ClickableViewAccessibility")
    private fun showFloatingWindow() {
        // 獲取WindowManager服務(wù)
        windowManager = getSystemService(Context.WINDOW_SERVICE) as WindowManager
 
        // 新建懸浮窗控件
        val view = LayoutInflater.from(this).inflate(R.layout.window, null)
 
        // 設(shè)置LayoutParam
        layoutParams = WindowManager.LayoutParams()
 
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            layoutParams.type = WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY
        } else {
            layoutParams.type = WindowManager.LayoutParams.TYPE_PHONE
        }
 
        //設(shè)置位置
        layoutParams.gravity = Gravity.LEFT or Gravity.TOP
 
        layoutParams.x = windowManager.defaultDisplay.width
        layoutParams.y = 200
 
        //設(shè)置flag
        layoutParams.flags =
            WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE or WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL or
                    WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN or WindowManager.LayoutParams.FLAG_LAYOUT_INSET_DECOR or
                    WindowManager.LayoutParams.FLAG_WATCH_OUTSIDE_TOUCH
        //設(shè)置view的寬高
        layoutParams.width = WindowManager.LayoutParams.WRAP_CONTENT
        layoutParams.height = WindowManager.LayoutParams.WRAP_CONTENT
 
        //添加拖拽事件
        view.setOnTouchListener(FloatingOnTouchListener())
 
        val close = view.findViewById<ImageView>(R.id.close)
 
        close.setOnClickListener {
            stopSelf()
            windowManager.removeView(view)
            Toast.makeText(this,"close",Toast.LENGTH_SHORT).show()
        }
 
        // 將懸浮窗控件添加到WindowManager
        windowManager.addView(view, layoutParams)
    }
 
    override fun onDestroy() {
        super.onDestroy()
        Toast.makeText(this,"onDestroy",Toast.LENGTH_SHORT).show()
    }
 
    inner class FloatingOnTouchListener : View.OnTouchListener {
 
        private var x = 0f
        private var y = 0f
 
        @SuppressLint("ClickableViewAccessibility")
        override fun onTouch(v: View?, event: MotionEvent?): Boolean {
            when(event?.action){
 
                MotionEvent.ACTION_DOWN ->{
                    x = event.rawX
                    y = event.rawY
                }
 
                MotionEvent.ACTION_MOVE ->{
                    val nowX = event.rawX
                    val nowY = event.rawY
                    val movedX = nowX - x
                    val movedY = nowY - y
                    x = nowX
                    y = nowY
                    layoutParams.x = (layoutParams.x + movedX).toInt()
                    layoutParams.y = (layoutParams.y + movedY).toInt()
                    windowManager.updateViewLayout(v, layoutParams)
                }
 
                MotionEvent.ACTION_UP ->{
 
                }
 
            }
            return false
        }
    }
}

package com.example.floatingwindow
 
import android.content.Intent
import android.net.Uri
import android.os.Build
import android.os.Bundle
import android.provider.Settings
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
 
 
class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        startFloatingService()
    }
 
    private fun startFloatingService() {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            if (!Settings.canDrawOverlays(this)) {
                startActivityForResult(Intent(Settings.ACTION_MANAGE_OVERLAY_PERMISSION, Uri.parse("package:$packageName")), 0)
            } else {
                startService(Intent(this@MainActivity, FloatingWindowService::class.java))
            }
        }
    }
 
    override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
        super.onActivityResult(requestCode, resultCode, data)
        if (requestCode == 0) {
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                if (!Settings.canDrawOverlays(this)) {
                    Toast.makeText(this, "授權(quán)失敗", Toast.LENGTH_SHORT).show()
                } else {
                    Toast.makeText(this, "授權(quán)成功", Toast.LENGTH_SHORT).show()
                    startService(Intent(this@MainActivity, FloatingWindowService::class.java))
                }
            }
        }
    }
}