我的印象是，如果片段放在onStart（）和onResume方法中，一旦片段启动就可以触发onEvent。请看下面我的片段。这个方法prepareListData是在我显示它之前对列表进行排序但是onEvent（包含来自另一个片段的列表数据）由于某种原因在prepareListData（）之后被调用，这意味着没有实际列表，因此我得到一个空指针。如何在prepareListData
之前调用onEvent import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import android.content.Context;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.view.ViewPager;
import android.util.Log;
import android.view.View;
//import android.widget.ExpandableListAdapter;
import android.widget.ExpandableListView;
import android.widget.Toast;
import android.support.annotation.Nullable;
import android.view.LayoutInflater;
import android.view.ViewGroup;
import com.androidquery.AQuery;
import com.xera.deviceinsight.Errors;
import com.xera.deviceinsight.Globals;
import com.xera.deviceinsight.R;
import com.xera.deviceinsight.api.OrganisationDeviceSensorsResult;
import com.xera.deviceinsight.api.Results;
import com.xera.deviceinsight.net.Claritech;
import com.xera.deviceinsight.net.ClaritechClient;
import com.xera.deviceinsight.receivers.IEvent;
import com.xera.deviceinsight.sensors.IotTabFragment;
import com.xera.deviceinsight.sensors.ItemClickedEvent;
import com.xera.deviceinsight.structs.DistanceUpdatedEvent;
import com.xera.deviceinsight.structs.HelloWorldEvent;
import com.xera.deviceinsight.structs.OrganisationDeviceSensorsEvent;
public class CostCentreListFragment extends Fragment {
public static final String TAG = Globals.TAG + ".ALF";
ViewPager mViewPager;
ExpandableListAdapter listAdapter;
ExpandableListView expListView;
List<String> listDataHeader;
HashMap<String, List<String>> listDataChild;
public static List<OrganisationDeviceSensorsResult> Items;
public String currentReportingGroup;
private ViewPager viewPager;
private IEvent onDeviceSensorsObtained;
private IEvent event;
public List sensorList;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
//EventBus eventBus = EventBus.getDefault();
//if (!eventBus.isRegistered(this)) eventBus.register(this);
View view = inflater.inflate(R.layout.layout_expandable, container, false);
AQuery aq = new AQuery(view);
expListView = (ExpandableListView) view.findViewById(R.id.lvExp);
//prepareListData();
prepareSensorListData();
listAdapter = new ExpandableListAdapter(this.getActivity(), listDataHeader, listDataChild);
// setting list adapter
listAdapter = new ExpandableListAdapter(this.getActivity(), listDataHeader, listDataChild);
expListView.setAdapter(listAdapter);
expListView.setOnChildClickListener(new ExpandableListView.OnChildClickListener() {
@Override
public boolean onChildClick(ExpandableListView parent, View v, int groupPosition, int childPosition, long id) {
//Nothing here ever fires
System.err.println("child clicked");
Toast.makeText(getActivity(), "child clicked", Toast.LENGTH_SHORT).show();
// Navigate to second tab
EventBus.getDefault().post(new ItemClickedEvent(IotTabFragment.TAB_SENSOR));
return true;
}
});
return view;
}
@Override
public void onStart() {
super.onStart();
EventBus.getDefault().register(this);
}
@Override
public void onPause() {
EventBus.getDefault().unregister(this);
super.onPause();
}
private void getDeviceSensorCostCentres() {
//int costCentreID =0
final Context context = this.getActivity();
ClaritechClient client = new ClaritechClient(context);
Claritech.api(context).getDeviceSensorCostCentres(client.getCostCentreID()).enqueue(new Callback<Results<OrganisationDeviceSensorsResult>>() {
@Override
public void onResponse(Call<Results<OrganisationDeviceSensorsResult>> call, Response<Results<OrganisationDeviceSensorsResult>> response) {
if (response.isSuccessful()) {
// Reload data source
Items.clear();
Items.addAll(response.body());
//ItemsAdapter.notifyDataSetChanged();
Log.i(TAG, "onResponse: ");
}
}
@Override
public void onFailure(Call<Results<OrganisationDeviceSensorsResult>> call, Throwable t) {
Errors.handleException(t);
}
});
}
public void onEvent(OrganisationDeviceSensorsEvent event){
String Tag ="";
sensorList = event.deviceSensors;
Log.i("EventBus",Tag);
//prepareSensorListData();
//Toast.makeText(getActivity(), event.deviceSensors, Toast.LENGTH_SHORT).show();
};
private void prepareSensorListData() {
final Context context = this.getActivity();
ClaritechClient client = new ClaritechClient(context);
Claritech.api(context).getDeviceSensorCostCentres(client.getCostCentreID()).enqueue(new Callback<Results<OrganisationDeviceSensorsResult>>() {
@Override
public void onResponse(Call<Results<OrganisationDeviceSensorsResult>> call, Response<Results<OrganisationDeviceSensorsResult>> response) {
if (response.isSuccessful()) {
// Reload data source
Items.clear();
Items.addAll(response.body());
//ItemsAdapter.notifyDataSetChanged();
Log.i(TAG, "onResponse: ");
String Tag ="";
listDataHeader = new ArrayList<String>();
listDataChild = new HashMap<String, List<String>>();
Log.i("EventBus",Tag);
//List sensorList = event.deviceSensors;
int check = sensorList.size();
int check2 = Items.size();
List<String> top250 = new ArrayList<String>();
for (int i = 1; i < Items.size(); i++) {
//if(i!=1 && sensorList.get(i).= currentReportingGroup)
// do a check here to see if the reporting group has changed or not
{
listDataHeader.add(Items.get(i).ReportingGroup);
top250.add(Items.get(i).SensorLocation);
// top250.add(String.valueOf(Items.get(i).SensorID));
}
}
listDataChild.put(listDataHeader.get(0), top250);
}
}
@Override
public void onFailure(Call<Results<OrganisationDeviceSensorsResult>> call, Throwable t) {
Errors.handleException(t);
}
});
};
}
答案 0 :(得分：1)
onEvent
EventBus.getDefault（）后（organisationDeviceSensorsEvent）;
IFF EventBus已注册，因此，如果您的片段已启动并正在运行。 不，恢复片段时不会调用它。当您恢复片段时，您注册EventBus侦听器以等待事件。何时发布事件＆＃34; onEvent（）{}＆＃34;正在被召唤。
如果发布粘性事件，您可以执行类似的操作（在EventBut文档中阅读如何发布以及如何获取它）。在这种情况下，您可以在某个随机时间点发布事件，如果您的片段正在运行或注册了侦听器，您的片段将同时接收它。但是，再次，
正在onCreateView上调用prepareSensorListData（）;
，因此在EventBus注册之前将调用它。