class MyService : Service() {

    val mBinder=DownLoadBinder()

    // 继承Binder,内部提供下载方法
    class DownLoadBinder:Binder(){

        fun startDownload(){
            Log.e("MYService", "startDownload: ", )
        }

        fun getProgress(){
            Log.e("MYService", "getProgress: ", )
        }
    }


    override fun onBind(intent: Intent): IBinder {

        return mBinder
    }


    // service创建时调用
    override fun onCreate() {
        Log.e("service", "onCreate: ")
        super.onCreate()
    }

    // 在每次service启动时调用
    override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
        Log.e("service", "onStartCommand: ", )
        return super.onStartCommand(intent, flags, startId)
    }

    // 在service销毁时调用
    override fun onDestroy() {
        Log.e("service", "onDestroy: ", )
        super.onDestroy()
    }
}

/**
 * 在activity中和service绑定
 * 1.创建类并继承自service
 * 2.在manifests中进行注册
 * 3.在service中定义类继承自binder
 * 3.1.           重写onbind方法返回binder类
 * 4、在activity中声明binder变量
 * 4.1在activity中声明一个实现了ServiceConnection对象
 * 4.1.1重写onServiceConnection方法 当activity和service绑定时调用
 * 4.1.2重写onServiceDisconnected方法 当service崩溃了或被强杀时调用
 * 5.启动，绑定service对象
 * 5.1.1 启动service ,使用Context对象的startService(Intent)
 * 5.1.2 关闭service stopSer(Intent) Intent(this:Context,MyService::class.java)
 * 5.2.1 绑定service 使用Context对象bindService(Intent,Connection,flag)
 * 5.2.2 解绑service unbindService(Connection)
 *
 * service生命周期 创建时调用onCreate
 *                启动时调用onStartCommand
 *                绑定时调用onBind
 *                销毁时调用onDestroy
 *  当service 启动并绑定 需关闭service并解绑才会 onDestroy
 */
class MainActivity : AppCompatActivity() {

    lateinit var binding:ActivityMainBinding

    // 声明binder变量
    lateinit var downloadBinder:MyService.DownLoadBinder

    // 创建一个匿名对象并实现ServiceConnection接口
    val connection = object : ServiceConnection {
        // service 绑定时调用
        override fun onServiceConnected(name: ComponentName?, service: IBinder?) {
            downloadBinder = service as MyService.DownLoadBinder
            downloadBinder.startDownload()
            downloadBinder.getProgress()
        }

        // service 崩溃或被强杀时调用
        override fun onServiceDisconnected(name: ComponentName?) {
            Log.e("activity", "onServiceDisconnected: ", )
        }
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding = ActivityMainBinding.inflate(layoutInflater)

        setContentView(binding.root)

        binding.btnStart.setOnClickListener {
            val intent:Intent = Intent(this,MyService::class.java)
            // 启动service
            startService(intent)
        }

        binding.btnStop.setOnClickListener {
            val intent=Intent(this,MyService::class.java)
            // 停止service
            stopService(intent)
        }

        binding.btnBind.setOnClickListener {
            val intent=Intent(this,MyService::class.java)
            // 绑定service
            bindService(intent,connection, Context.BIND_AUTO_CREATE)
        }

        binding.btnUnbind.setOnClickListener {
            // 解绑service
            unbindService(connection)
        }
    }
}

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/btn_start"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="56dp"
        android:layout_marginTop="308dp"
        android:text="启动service"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/btn_stop"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="256dp"
        android:layout_marginTop="308dp"
        android:text="关闭service"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />


    <Button
        android:id="@+id/btn_unbind"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="256dp"
        android:layout_marginTop="428dp"
        android:text="unbind"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/btn_bind"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="72dp"
        android:layout_marginTop="420dp"
        android:text="bind"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>