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史上最简洁Kotlin版EventBus的使用教程


EventBus简介

  • EventBus是一种用于Android的事件发布-订阅总线。他简化了应用程序内各个组件之间进行通信的复杂度。

​​GitHub - greenrobot/EventBus: Event bus for Android and Java that simplifies communication between Activities, Fragments, Threads, Services, etc. Less code, better quality.


https://github.com/greenrobot/EventBus​​

EventBus使用步骤 

        1、配置gradle,导入依赖

implementation 'org.greenrobot:eventbus:3.3.1'

非必须)

package com.example.eventbusdemo

data class MessageEvent(val name: String) {

}

        3、注册、注销EventBus

override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
//注册订阅者
//避免重复注册,重复注册会导致崩溃
if (!EventBus.getDefault().isRegistered(this)) { //这里的取反别忘记了
EventBus.getDefault().register(this)
} else {
println("请勿重复注册事件")
}
}

override fun onDestroy() {
super.onDestroy()
//注销订阅者
EventBus.getDefault().unregister(this)
}

        4、定义事件处理订阅者

//准备接受事件的订阅者
@Subscribe(threadMode = ThreadMode.MAIN)
fun onMessageEvent(event: MessageEvent) {
println(event.name)
}

        5、创建并发送消息

fun sendEvent(v: View) {
EventBus.getDefault().post(MessageEvent("我来自第二个页面"))
}

运行效果展示

史上最简洁Kotlin版EventBus的使用教程_android

常见问题总结

1、Caused by: org.greenrobot.eventbus.EventBusException: Subscriber class com.example.eventbusdemo.SecondActivity and its super classes have no public methods with the @Subscribe annotation

Caused by: org.greenrobot.eventbus.EventBusException: Subscriber class com.example.eventbusdemo.SecondActivity and its super classes have no public methods with the @Subscribe annotation
at org.greenrobot.eventbus.SubscriberMethodFinder.findSubscriberMethods(SubscriberMethodFinder.java:67)
at org.greenrobot.eventbus.EventBus.register(EventBus.java:150)
at com.example.eventbusdemo.SecondActivity.onCreate(SecondActivity.kt:20)
at android.app.Activity.performCreate(Activity.java:7893)
at android.app.Activity.performCreate(Activity.java:7880)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1306)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3313)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3487)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2071)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:224)
at android.app.ActivityThread.main(ActivityThread.java:7561)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:539)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:995)

问题原因:你这个类注册了 EventBus 可是这个类没有写带 @Subscribe 注解的方法

解决方法:补上该方法即可

2、D/EventBus: No subscribers registered for event class com.example.eventbusdemo.MessageEvent
      D/EventBus: No subscribers registered for event class org.greenrobot.eventbus.NoSubscriberEvent

D/EventBus: No subscribers registered for event class com.example.eventbusdemo.MessageEvent
D/EventBus: No subscribers registered for event class org.greenrobot.eventbus.NoSubscriberEvent

问题原因:EventBus没有被注册上,检查 EventBus 的注册代码

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