android - 带有Fragments和EventBus的空指针异常

我已经通过各种方法使这个项目的工作，并最终确定了从绿色机器人事件总线。关于这一点，我的第二个问题是：-Multiple Fragment to Activity communication。
我被引导到那里的活动巴士路线上。我已经加入了适当的图书馆，我想我已经很接近使它发挥作用。无论哪一行包含

eBus.post(Str);

我相当肯定，因为我没有正确注册ebus。我知道一个片段没有这样的上下文，但我也尝试过使用getActivity（）也没有用。我已经发布了下面的主要活动，corefragment和logcat。如果有人能帮忙，我将不胜感激。这已经持续了近一个月，断断续续！！

import de.greenrobot.event.EventBus;
import android.os.Bundle;
import android.app.Activity;
import android.util.Log;
import android.view.Menu;
import android.widget.EditText;

public class MainActivity extends Activity {

EditText editText1;
String Txt;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    editText1 = (EditText) findViewById(R.id.editText1);
    Txt = "";
    EventBus eBus = new EventBus();
    eBus.register(this);<--This I removed.
        eBus.getDefault().register(this);<--This is the new line you suggested
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.activity_main, menu);
    return true;
}

public void onEvent(String event){
    Txt = Txt + event;
    editText1.setText(Txt);<--Left this as it was,it worked
}


}//End

下面是片段代码：

import de.greenrobot.event.EventBus;
import android.app.Activity;
import android.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.os.Bundle;
import android.widget.Button;
import android.widget.RelativeLayout;
import android.view.View.OnClickListener;


public class CoreFragment extends Fragment{

int index;
Button Button1,Button2,Button3;
String Str,data;
EventBus eBus;


@Override
public void onAttach(Activity a) {
    super.onAttach(a);
    EventBus eBus = new EventBus();
    eBus.getDefault().register(this);
    }


public static CoreFragment newInstance(int index) {
    CoreFragment coreFragment = new CoreFragment();
    coreFragment.index = index;
    return coreFragment;
}

public void onEvent(String event){
// Crash Stopper
    }

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


    if (container == null) {
        // We have different layouts, and in one of them this
        // fragment's containing frame doesn't exist. The fragment
        // may still be created from its saved state, but there is
        // no reason to try to create its view hierarchy because it
        // won't be displayed. Note this is not needed -- we could
        // just run the code below, where we would create and return
        // the view hierarchy; it would just never be used.
        return null;
    }
    RelativeLayout mRelativeLayout = (RelativeLayout) inflater.inflate(R.layout.corefragment,
            container, false);

    Button Button1 = (Button) mRelativeLayout.findViewById(R.id.Button1);
    Button Button2 = (Button) mRelativeLayout.findViewById(R.id.Button2);
    Button Button3 = (Button) mRelativeLayout.findViewById(R.id.Button3);

    Button1.setOnClickListener(new OnClickListener() {
    @Override
    public void onClick(View v) {
    Str = "I ";
    eBus.post(Str);<--Old code, removed in working version
        eBus.getDefault().post(Str);<--Changed as suggested
    }

         });

    Button2.setOnClickListener(new OnClickListener() {
    @Override
    public void onClick(View v) {
        Str = "want ";
    eBus.post(Str);<--Old code, removed in working version
        eBus.getDefault().post(Str);<--Changed as suggested
    }

         });

    Button3.setOnClickListener(new OnClickListener() {
    @Override
    public void onClick(View v) {
        Str = "more ";
    eBus.post(Str);<--Old code, removed in working version
        eBus.getDefault().post(Str);<--Changed as suggested
    }

         });

    return mRelativeLayout;
}


}//end

我尝试过各种排列，例如ebus.register（this）；、ebus.register（this，string.class）；、ebus.register（getActivity（））；等等。
这是按下按钮1时的日志：

02-13 13:56:40.717: W/dalvikvm(26237): threadid=1: thread exiting with uncaught exception (group=0x40acf228)
02-13 13:56:40.747: E/AndroidRuntime(26237): FATAL EXCEPTION: main
02-13 13:56:40.747: E/AndroidRuntime(26237): java.lang.NullPointerException
02-13 13:56:40.747: E/AndroidRuntime(26237):    at com.epsilonitsystems.fragger.CoreFragment$1.onClick(CoreFragment.java:65)
02-13 13:56:40.747: E/AndroidRuntime(26237):    at android.view.View.performClick(View.java:3549)
02-13 13:56:40.747: E/AndroidRuntime(26237):    at android.view.View$PerformClick.run(View.java:14393)
02-13 13:56:40.747: E/AndroidRuntime(26237):    at android.os.Handler.handleCallback(Handler.java:605)
02-13 13:56:40.747: E/AndroidRuntime(26237):    at android.os.Handler.dispatchMessage(Handler.java:92)
02-13 13:56:40.747: E/AndroidRuntime(26237):    at android.os.Looper.loop(Looper.java:154)
02-13 13:56:40.747: E/AndroidRuntime(26237):    at android.app.ActivityThread.main(ActivityThread.java:4945)
02-13 13:56:40.747: E/AndroidRuntime(26237):    at java.lang.reflect.Method.invokeNative(Native Method)
02-13 13:56:40.747: E/AndroidRuntime(26237):    at java.lang.reflect.Method.invoke(Method.java:511)
02-13 13:56:40.747: E/AndroidRuntime(26237):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
02-13 13:56:40.747: E/AndroidRuntime(26237):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
02-13 13:56:40.747: E/AndroidRuntime(26237):    at dalvik.system.NativeStart.main(Native Method)

我试过的各种编译方法都很好，没有错误，但每次按下屏幕上的按钮都会强制关闭。
有什么想法吗？？谢谢。

最佳答案

尝试以下建议：
1。注册到事件总线的任何位置使用：

EventBus.getDefault().register(this);

2。当您要发布事件时，请使用：

EventBus.getDetault().post(new MyEvent(aString));

三.如果要更改UI，请确保将事件方法命名为：

 public void onEventMainThread(MyEvent event){
        editText1.setText(event.getString());
    }

4。定义一个事件类来保存结果：

public class MyEvent(){
  private mString;

  public MyEvent(String string){
    mString = string;
  }

  public getString(){
    return mString;
  }
}

5。不要忘记通过调用以下命令从EventBus注销组件：

EventBus.getDefault().unregister(this);