什么是Service

Service又称服务,是一种可在后台执行长耗时操作的无操作界面组件.Service可以被像Activity这样的组件启动,启动后,就在后台一直运行,即使启动它的组件销毁了也不影响Service的运行.启动Service的组件可以和Service进行绑定来进行通信,如播放音乐等.

创建Service

1. 在工程目录中单击右键,选择“New>Service>Service”

   
   

2. 在窗口中设置Service名称(其他设置保持默认即可)

   
   
3. 创建后的Service如下

class MyService : Service() {
    override fun onBind(intent: Intent): IBinder {
        TODO("Return the communication channel to the service.")
    }
}

4. 查看AndroidManifest.xml文件,里面应该已经增加了如下Service配置.

<manifest ...>
    <application ...>
        <service
            android:name=".MyService"
            android:enabled="true"
            android:exported="true"></service>
      ...
    </application>
</manifest>

使用Service

Service有两种使用方式:

1. 通过startService启动Service
   一旦启动后,服务就在后台执行,即使启动它的组件已销毁也不受影响,除非调用stopService来停止它.
2. 通过bindService绑定Service
   Service被绑定后,一样可以在后台执行,同时还可以和绑定它的组件通信.一个Service可以被多个组件绑定.当所有组件都和它解绑后,那Service就会销毁.

启动Service样例

1. Service代码:MyService.kt

class MyService : Service() {

    override fun onCreate() {
        Log.d("MyService", "onCreate")
        super.onCreate()
    }

    override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
        Log.d("MyService", "onStartCommand")
        thread {
            study()
        }
        return super.onStartCommand(intent, flags, startId)
    }

    private fun study() {
        for (index in 1..10) {
            Log.d("MyService", "我在学习，我在学习，没偷懒")
            Thread.sleep(2000)
        }
    }

    override fun onDestroy() {
        Log.d("MyService", "onDestroy")
        super.onDestroy()
    }

    override fun onBind(intent: Intent?): IBinder? {
        return null
    }
}

2. 调用代码

class MainActivity : AppCompatActivity() {

    private lateinit var serviceIntent: Intent
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        //启动Service
        serviceIntent = Intent(this, MyService::class.java)
        startService(serviceIntent)
    }

    override fun onDestroy() {
        super.onDestroy()
        //停止Service
        stopService(serviceIntent)
    }
}

绑定Service样例

1. Service代码:MyService.kt

class MyService : Service() {
    inner class MyBinder : Binder() {

        fun study() {
            Log.d("MyService", "开始学习")
        }

        fun getProgress() {
            Log.d("MyService", "当前进度：50%")
        }
    }

    private val binder = MyBinder()
    override fun onBind(intent: Intent?): IBinder? {
        return binder
    }
}

2. 调用代码

class MainActivity : AppCompatActivity() {
    var myBinder: MyService.MyBinder? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        initListeners()
    }

    private fun initListeners() {
        //绑定Service
        bindBtn.setOnClickListener {
            val intent = Intent(this, MyService::class.java)
            bindService(intent, serviceConnection, BIND_AUTO_CREATE)
        }
        
        //解绑Service
        unBindBtn.setOnClickListener { unbindService(serviceConnection) }

        //通过绑定关系和Service通信，调用Service里的方法
        studyBtn.setOnClickListener { myBinder?.study() }
        progressBtn.setOnClickListener { myBinder?.getProgress() }
    }

    /**
     * 创建Service绑定连接
     */
    private val serviceConnection = object : ServiceConnection {
        override fun onServiceConnected(name: ComponentName, binder: IBinder) {
            myBinder = binder as MyService.MyBinder
        }

        override fun onServiceDisconnected(name: ComponentName) {}
    }
}

完整源代码

https://gitee.com/cxyzy1/AndroidServiceDemo