android - Greenrobot 的 Eventbus：调用异步任务作业的两个片段让 Eventbus 感到困惑

Question

我目前正在研究Fragments是在 with 下创建Activities的FragmentPagerAdapter。我使用 GreenRobot 的 EventBus 3.0 返回一些我从服务类创建的 AsyncTask。然而，由于这两个片段是一个接一个地创建的，事件总线的帖子粘性的返回使订阅的片段混淆了。我已经浏览了stackoverflow，做了其他人所做的（例如将eventBus寄存器放到onStart和OnStop等），但我仍然看不到类似的问题。希望您能够帮助我。谢谢！

这是我的两个片段：（我省略了一些不必要的代码）

1.状态片段

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    Log.e(TAG, "StatusFragment onCreateView");
    eventBus = EventBus.getDefault();
    eventBus.register(this);
    StatusService statusService = StatusService.newInstance(getContext());
    statusService.getStatusList(); //Async Task to call onReturnAdapter once finished
    return mRecyclerView;
}

@Subscribe(sticky = true, threadMode = ThreadMode.MAIN)
public void onReturnList(List<Status> statuses) {
    Log.e(TAG, "onReturnList");
    mAdapter = new StatusRecyclerAdapter(statuses);
    mRecyclerView.setAdapter(mAdapter);
    eventBus.removeStickyEvent(statuses);
}

@Override
public void onStop() {
    Log.e(TAG, "onStop");
    eventBus.unregister(this);
    super.onStop();
}

2. 状态服务——状态片段的服务类

public void getStatusList () {
    Log.e(LOG_TAG, "getStatusList");
    //do some async tasks here
    returnList(statuses);

}

private void returnList(List<Status> statuses) {
    Log.e(LOG_TAG, "returnList");
    eventBus.postSticky(statuses);
}

3.图表片段

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {

    Log.e(LOG_TAG, "onCreateView");

    eventBus = EventBus.getDefault();
    eventBus.register(this);

    chartService = ChartService.newInstance(getContext());
    chartService.getDateResult(new DbRequestFeelings());
    return view;
}

@Subscribe(sticky = true, threadMode = ThreadMode.MAIN)
public void onReturnResults(List<Result> results) {
    Log.e(LOG_TAG, "onReturnResults");

    chartService.setupPieChart(results, feelingsPieChart);
}

@Override
public void onStop() {
    eventBus.unregister(this);
    super.onStop();
}

4. 海图服务

public void getDateResult(final DbRequest dbRequest) {
    Log.e(LOG_TAG, "getDateResult");
    //do some async tasks
    returnResults(results);
}

private void returnResults(List<Result> results) {
    Log.e(LOG_TAG, "returnResults");
    eventBus.postSticky(results);
}

5.结果类

public class Result {
      ....
}

6.状态类

public class Status {
    ...
}

因此，每次创建片段时，它们都会调用其服务类，该服务类依次发布，List<Status>并且List<Results>几乎一个接一个地发布。因此，它在说

03-11 11:48:19.685  15148-15148/com.paularagones.moode E/EventBus﹕ Could not dispatch event: class java.util.ArrayList to subscribing class class com.paularagones.moode.Fragments.ChartFragment
    java.lang.ClassCastException: com.paularagones.moode.Models.Status cannot be cast to com.paularagones.moode.Models.Result

这是完整的堆栈跟踪：

03-11 11:48:19.589  15148-15148/com.paularagones.moode E/Moode-StatusFragment﹕ StatusFragment onCreate
03-11 11:48:19.589  15148-15148/com.paularagones.moode E/Moode-StatusFragment﹕ StatusFragment onCreateView
03-11 11:48:19.605  15148-15148/com.paularagones.moode E/StatusService﹕ getStatusList
03-11 11:48:19.609  15148-15148/com.paularagones.moode E/ChartFragment﹕ onCreateView
03-11 11:48:19.613  15148-15148/com.paularagones.moode E/ChartService﹕ newInstance
03-11 11:48:19.621  15148-15148/com.paularagones.moode E/ChartService﹕ getDateResult
03-11 11:48:19.681  15148-15148/com.paularagones.moode E/RecyclerView﹕ No adapter attached; skipping layout
03-11 11:48:19.681  15148-15148/com.paularagones.moode E/StatusService﹕ returnList
03-11 11:48:19.681  15148-15148/com.paularagones.moode E/Moode-StatusFragment﹕ onReturnList
03-11 11:48:19.681  15148-15148/com.paularagones.moode E/ChartFragment﹕ onReturnResults
03-11 11:48:19.685  15148-15148/com.paularagones.moode E/EventBus﹕ Could not dispatch event: class java.util.ArrayList to subscribing class class com.paularagones.moode.Fragments.ChartFragment
    java.lang.ClassCastException: com.paularagones.moode.Models.Status cannot be cast to com.paularagones.moode.Models.Result
            at com.paularagones.moode.Services.ChartService.getData(ChartService.java:147)
            at com.paularagones.moode.Services.ChartService.setupPieChart(ChartService.java:129)
            at com.paularagones.moode.Fragments.ChartFragment.onReturnResults(ChartFragment.java:116)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at org.greenrobot.eventbus.EventBus.invokeSubscriber(EventBus.java:485)
            at org.greenrobot.eventbus.EventBus.postToSubscription(EventBus.java:420)
            at org.greenrobot.eventbus.EventBus.postSingleEventForEventType(EventBus.java:397)
            at org.greenrobot.eventbus.EventBus.postSingleEvent(EventBus.java:370)
            at org.greenrobot.eventbus.EventBus.post(EventBus.java:251)
            at org.greenrobot.eventbus.EventBus.postSticky(EventBus.java:292)
            at com.paularagones.moode.Services.StatusService.returnList(StatusService.java:80)
            at com.paularagones.moode.Services.StatusService.access$100(StatusService.java:24)
            at com.paularagones.moode.Services.StatusService$2.onNext(StatusService.java:72)
            at com.paularagones.moode.Services.StatusService$2.onNext(StatusService.java:59)
            at rx.Observable$30.onNext(Observable.java:8069)
            at rx.observers.SafeSubscriber.onNext(SafeSubscriber.java:139)
            at rx.internal.operators.OperatorObserveOn$ObserveOnSubscriber.pollQueue(OperatorObserveOn.java:202)
            at rx.internal.operators.OperatorObserveOn$ObserveOnSubscriber$2.call(OperatorObserveOn.java:162)
            at rx.internal.schedulers.ScheduledAction.run(ScheduledAction.java:55)
            at android.os.Handler.handleCallback(Handler.java:615)
            at android.os.Handler.dispatchMessage(Handler.java:92)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:4745)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
            at dalvik.system.NativeStart.main(Native Method)
03-11 11:48:19.685  15148-15148/com.paularagones.moode E/ChartService﹕ returnResults
03-11 11:48:19.685  15148-15148/com.paularagones.moode E/Moode-StatusFragment﹕ onReturnList
03-11 11:48:19.685  15148-15148/com.paularagones.moode E/ChartFragment﹕ onReturnResults
03-11 11:48:19.693  15148-15148/com.paularagones.moode E/StatusRecyclerAdapter﹕ onCreateViewHolder
03-11 11:48:19.697  15148-15148/com.paularagones.moode E/StatusRecyclerAdapter﹕ onBindViewHolder
03-11 11:48:19.709  15148-15148/com.paularagones.moode E/AndroidRuntime﹕ FATAL EXCEPTION: main
    java.lang.ClassCastException: com.paularagones.moode.Models.Result cannot be cast to com.paularagones.moode.Models.Status
            at com.paularagones.moode.Adapters.StatusRecyclerAdapter.onBindViewHolder(StatusRecyclerAdapter.java:101)
            at com.paularagones.moode.Adapters.StatusRecyclerAdapter.onBindViewHolder(StatusRecyclerAdapter.java:28)
            at android.support.v7.widget.RecyclerView$Adapter.onBindViewHolder(RecyclerView.java:5277)
            at android.support.v7.widget.RecyclerView$Adapter.bindViewHolder(RecyclerView.java:5310)
            at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:4568)
            at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:4461)
            at android.support.v7.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:1962)
            at android.support.v7.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1371)
            at android.support.v7.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1334)
            at android.support.v7.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:563)
            at android.support.v7.widget.RecyclerView.dispatchLayout(RecyclerView.java:2847)
            at android.support.v7.widget.RecyclerView.onLayout(RecyclerView.java:3145)
            at android.view.View.layout(View.java:13754)
            at android.view.ViewGroup.layout(ViewGroup.java:4362)
            at android.support.v4.view.ViewPager.onLayout(ViewPager.java:1627)
            at android.view.View.layout(View.java:13754)
            at android.view.ViewGroup.layout(ViewGroup.java:4362)
            at android.support.design.widget.CoordinatorLayout.layoutChild(CoordinatorLayout.java:1034)
            at android.support.design.widget.CoordinatorLayout.onLayoutChild(CoordinatorLayout.java:744)
            at android.support.design.widget.ViewOffsetBehavior.onLayoutChild(ViewOffsetBehavior.java:42)
            at android.support.design.widget.AppBarLayout$ScrollingViewBehavior.onLayoutChild(AppBarLayout.java:1180)
            at android.support.design.widget.CoordinatorLayout.onLayout(CoordinatorLayout.java:757)
            at android.view.View.layout(View.java:13754)
            at android.view.ViewGroup.layout(ViewGroup.java:4362)
            at android.widget.FrameLayout.onLayout(FrameLayout.java:448)
            at android.view.View.layout(View.java:13754)
            at android.view.ViewGroup.layout(ViewGroup.java:4362)
            at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1649)
            at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1507)
            at android.widget.LinearLayout.onLayout(LinearLayout.java:1420)
            at android.view.View.layout(View.java:13754)
            at android.view.ViewGroup.layout(ViewGroup.java:4362)
            at android.widget.FrameLayout.onLayout(FrameLayout.java:448)
            at android.view.View.layout(View.java:13754)
            at android.view.ViewGroup.layout(ViewGroup.java:4362)
            at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1649)
            at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1507)
            at android.widget.LinearLayout.onLayout(LinearLayout.java:1420)
            at android.view.View.layout(View.java:13754)
            at android.view.ViewGroup.layout(ViewGroup.java:4362)
            at android.widget.FrameLayout.onLayout(FrameLayout.java:448)
            at android.view.View.layout(View.java:13754)
            at android.view.ViewGroup.layout(ViewGroup.java:4362)
            at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:1866)
            at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1687)
            at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:998)
            at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4212)
            at android.view.Choreographer$CallbackRecord.run(Choreographer.java:725)
            at android.view.Choreographer.doCallbacks(Choreographer.java:555)
            at android.view.Choreographer.doFrame(Choreographer.java:525)
            at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:711)
            at android.os.Handler.handleCallback(Handler.java:615)
            at android.os.Handler.dispatchMessage(Handler.java:92)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:4745)
            at java.lang.reflect.Method.invokeNative(Native Method)

你们知道我的代码有什么问题吗？谢谢。

Answer 1

我注意到的第一件事是你没有去除你的onReturnResults(List<Result> results)方法中的粘性......不确定这是否是故意的......但认为应该提到它。

我想强调的主要一点是关于有两个 onEvent() 方法利用同一个泛型类List<>- 这很可能是问题 - 一个小的代码更改和快速测试可以验证这一点

class为每个创建一个List<>

public class Statuses
{
    List<Status> list;
    public Statuses(List<Status> data) { list = data; }
}

public class Results
{
    List<Result> list;
    public Results(List<Result> data) { list = data; }
}

更新您的 onEvent() 方法签名：

public void onReturnList(Statuses statuses)
public void onReturnResults(Results results)

更新您的 .postSticky() 方法调用：

eventBus.postSticky(new Statuses(statuses));
eventBus.postSticky(new Results(results));

当然，您需要从他们的班级成员访问列表（例如）：

foreach (var status in statuses.list)

和

foreach (var result in results.list)

如果您看到的问题在进行这些更改后就消失了 - 那么假设 greenrobot 的 EventBus 在调用堆栈中看到的反射调用期间没有考虑通用 List 类中包含的类型是有意义的。它可能只是寻找包含 List 参数的第一个匹配签名；当有 2 个或更多匹配时，正确的匹配可能不会被调用。

这是猜测；所以你必须尝试一下，看看它是否有帮助——但是当我需要类的 List<> 以避免歧义时，我已经在使用这种类型的实现的项目中成功使用了 greenrobot 的 EventBus。