Android EventBus的基本用法（kotlin版）

EventBus

https://github.com/greenrobot/EventBus

EventBus是一種用于Android的事件發布-訂閱總線，它簡化了應用程式內各個組件之間進行通信的復雜度，尤其是碎片之間進行通信的問題，可以避免由于使用廣播通信而帶來的諸多不便，

接收方

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        EventBus.getDefault().register(this)//注冊，重復注冊會導致崩潰
        MainActivity2.start(this)
    }

    override fun onDestroy() {
        super.onDestroy()
        EventBus.getDefault().unregister(this)//解綁
    }

    //接收訊息
    @Subscribe(threadMode = ThreadMode.MAIN)
    fun onMessageEvent(event: MessageEvent) {
        when (event.type) {
            MessageType.ShowLog -> {
                Log.e(TAG, "onMessageEvent: " + event.getString())
            }
            MessageType.ShowToast -> {
                Toast.makeText(this, "onMessageEvent: " + event.getString(), Toast.LENGTH_SHORT).show()
            }
        }
    }

}

發送方

    fun onClick(view: View) {
        when (view.id) {
            R.id.bt1 -> {
                EventBus.getDefault().post(MessageEvent(MessageType.ShowToast).put("hello"))
            }
            R.id.bt2 -> {
                EventBus.getDefault().post(MessageEvent(MessageType.ShowLog).put("你好"))
            }
        }
    }

發送的型別（封裝后只需要一個類即可，MessageType 來區分）

package maka.components.myeventbustest

import android.os.Bundle
import android.os.Parcelable
import java.io.Serializable

private const val KEY_INT = "key_int"
private const val KEY_STRING = "key_string"
private const val KEY_BOOL = "key_bool"
private const val KEY_SERIALIZABLE = "key_serializable"
private const val KEY_PARCELABLE = "key_parcelable"


data class MessageEvent(var type: MessageType) {

    var bundle = Bundle()

    fun put(value: Int): MessageEvent {
        bundle.putInt(KEY_INT, value)
        return this
    }

    fun put(value: String): MessageEvent {
        bundle.putString(KEY_STRING, value)
        return this
    }

    fun put(value: Boolean): MessageEvent {
        bundle.putBoolean(KEY_BOOL, value)
        return this
    }

    fun put(value: Serializable): MessageEvent {
        bundle.putSerializable(KEY_SERIALIZABLE, value)
        return this
    }

    fun put(value: Parcelable): MessageEvent {
        bundle.putParcelable(KEY_PARCELABLE, value)
        return this
    }

    fun put(key: String, value: Int): MessageEvent {
        bundle.putInt(key, value)
        return this
    }

    fun put(key: String, value: String): MessageEvent {
        bundle.putString(key, value)
        return this
    }

    fun put(key: String, value: Boolean): MessageEvent {
        bundle.putBoolean(key, value)
        return this
    }

    fun put(key: String, value: Serializable): MessageEvent {
        bundle.putSerializable(key, value)
        return this
    }

    fun put(key: String, value: Parcelable): MessageEvent {
        bundle.putParcelable(key, value)
        return this
    }

    //===============================================================

    fun getInt(): Int {
        return bundle.getInt(KEY_INT)
    }

    fun getString(): String? {
        return bundle.getString(KEY_STRING)
    }

    fun getBoolean(): Boolean {
        return bundle.getBoolean(KEY_BOOL)
    }

    fun <T : Serializable> getSerializable(): Serializable {
        return bundle.getSerializable(KEY_SERIALIZABLE) as T
    }

    fun <T : Parcelable> getParcelable(): T? {
        return bundle.getParcelable<T>(KEY_PARCELABLE)
    }

    fun getInt(key: String): Int {
        return bundle.getInt(key)
    }

    fun getString(key: String): String? {
        return bundle.getString(key)
    }

    fun getBoolean(key: String): Boolean {
        return bundle.getBoolean(key)
    }

    fun <T : Serializable> getSerializable(key: String): Serializable {
        return bundle.getSerializable(key) as T
    }

    fun <T : Parcelable> getParcelable(key: String): T? {
        return bundle.getParcelable<T>(key)
    }

}

enum class MessageType {
    ShowToast,
    ShowLog,
}

關于粘性事件的發送（先發送后注冊）

• 發送方，postSticky
• 接收方，sticky = true
• 先發送后注冊

接收（粘性事件）

    override fun onStart() {
        super.onStart()
        EventBus.getDefault().register(this)//注冊，重復注冊會導致崩潰
    }

    override fun onStop() {
        super.onStop()
        EventBus.getDefault().unregister(this)//解綁
    }

    //接收訊息
    @Subscribe(threadMode = ThreadMode.MAIN, sticky = true)
    fun onMessageEvent(event: MessageEvent) {
        when (event.type) {
            MessageType.ShowLog -> {
                viewBinding.tvShow.text = event.getString()
                Log.e(TAG, "onMessageEvent: " + event.getString())
            }
            MessageType.ShowToast -> {
                Toast.makeText(this, "onMessageEvent: " + event.getString(), Toast.LENGTH_SHORT)
                    .show()
            }
        }
    }

發送（粘性事件）

    fun onClick(view: View) {
        when (view.id) {
            R.id.bt1 -> {
                EventBus.getDefault().postSticky(MessageEvent(MessageType.ShowToast).put("hello"))
            }
            R.id.bt2 -> {
                EventBus.getDefault().postSticky(MessageEvent(MessageType.ShowLog).put("你好"))
            }
        }
    }