广播

• 标准广播
  异步、效率高
• 有序广播
  同步执行，优先级高的 BroadcastReceiver 先收到广播信息，调用 abortBroadcast() 截断正在传递的广播

注册广播

• 动态注册

class MainActivity : AppCompatActivity() {

    lateinit var timeChangeReceiver: TimeChangeReceiver

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        val intentFilter = IntentFilter()
        intentFilter.addAction("android.intent.action.TIME_TICK")
        timeChangeReceiver = TimeChangeReceiver()
        registerReceiver(timeChangeReceiver, intentFilter)
    }

    override fun onDestroy() {
        super.onDestroy()
        unregisterReceiver(timeChangeReceiver)
    }

    inner class TimeChangeReceiver : BroadcastReceiver() {
        override fun onReceive(context: Context, intent: Intent) {
            Toast.makeText(context, "Time has changed", Toast.LENGTH_SHORT).show()
        }
    }
}

• 静态注册
  →New→Other→Broadcast Receiver

Exported属性表示是否允许这个BroadcastReceiver 接收本程序以外的广播
Enabled属性表示是否启用这个BroadcastR eceiver

Android Studio 自动在 ANdroidManifest.xml文件中完成注册

发送广播

1. 发送标准广播

val intent = Intent("com.example.broadcasttest.MY_BROADCAST")
intent.setPackage(packageName) 
sendBroadcast(intent)

默认发送隐式广播，调用 setPackage() 传入要接收广播的应用程序包名，从而将它变成了显式广播，否则静态注册的BroadcastReceiver将无法接到这条广播。

2. 发送有序广播

sendOrderedBroadcast(intent, null)