Блог

Я использую метод обратного вызова для вызова метода из FragmentActivity в Fragment в проекте, который содержит также другой класс Activity.Я столкнулся с проблемой нулевого указателя из метода, вызываемого с помощью обратного вызова. Это трассировки logcat:

 06-19 05:36:42.090: I/Choreographer(888): Skipped 121 frames!  The application may be doing too much work on its main thread.
06-19 05:36:42.950: I/Choreographer(888): Skipped 60 frames!  The application may be doing too much work on its main thread.
06-19 05:36:43.230: D/gralloc_goldfish(888): Emulator without GPU emulation detected.
06-19 05:36:43.400: I/Choreographer(888): Skipped 39 frames!  The application may be doing too much work on its main thread.
06-19 05:37:06.300: I/Choreographer(888): Skipped 31 frames!  The application may be doing too much work on its main thread.
06-19 05:37:07.160: D/AndroidRuntime(888): Shutting down VM
06-19 05:37:07.160: W/dalvikvm(888): threadid=1: thread exiting with uncaught exception (group=0xb4af6ba8)
06-19 05:37:07.190: E/AndroidRuntime(888): FATAL EXCEPTION: main
06-19 05:37:07.190: E/AndroidRuntime(888): Process: info.androidhive.tabsswipe, PID: 888
06-19 05:37:07.190: E/AndroidRuntime(888): java.lang.NullPointerException
06-19 05:37:07.190: E/AndroidRuntime(888):  at info.androidhive.tabsswipe.MainFragment$1.onClick(MainFragment.java:48)
06-19 05:37:07.190: E/AndroidRuntime(888):  at android.view.View.performClick(View.java:4438)
06-19 05:37:07.190: E/AndroidRuntime(888):  at android.view.View$PerformClick.run(View.java:18422)
06-19 05:37:07.190: E/AndroidRuntime(888):  at android.os.Handler.handleCallback(Handler.java:733)
06-19 05:37:07.190: E/AndroidRuntime(888):  at android.os.Handler.dispatchMessage(Handler.java:95)
06-19 05:37:07.190: E/AndroidRuntime(888):  at android.os.Looper.loop(Looper.java:136)
06-19 05:37:07.190: E/AndroidRuntime(888):  at android.app.ActivityThread.main(ActivityThread.java:5017)
06-19 05:37:07.190: E/AndroidRuntime(888):  at java.lang.reflect.Method.invokeNative(Native Method)
06-19 05:37:07.190: E/AndroidRuntime(888):  at java.lang.reflect.Method.invoke(Method.java:515)
06-19 05:37:07.190: E/AndroidRuntime(888):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
06-19 05:37:07.190: E/AndroidRuntime(888):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
06-19 05:37:07.190: E/AndroidRuntime(888):  at dalvik.system.NativeStart.main(Native Method)
 

это мой фрагмент кода:

 package info.androidhive.tabsswipe;



import android.app.Activity;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.Toast;

public class MainFragment extends Fragment {

    public interface UiListener{
            public void onButtonClicked();
    }

     UiListener uiCallback;

    @Override
    public void onAttach(Activity activity) {               
            super.onAttach(activity);               
            try {
                //uiCallback = (UiListener) activity;
                uiCallback = (UiListener) getActivity().getSupportFragmentManager().findFragmentById(R.id.main_fragment);
            } catch (ClassCastException e) {
                throw new ClassCastException(activity.toString()
                          " must implement UiListener");
            }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                    Bundle savedInstanceState) {
            return inflater.inflate(R.layout.fragment_main, container, false);
    }

    @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
            super.onViewCreated(view, savedInstanceState);

            view.findViewById(R.id.button).setOnClickListener(new OnClickListener() {                       

                    public void onClick(View v) {

                            uiCallback.onButtonClicked();

                    }
            });
}
}
 

И это код действия фрагмента

 package info.androidhive.tabsswipe;

import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.widget.Toast;

   public  class TopRatedFragment extends FragmentActivity implements MainFragment.UiListener{
    private MainFragment fragment;
    @Override
    protected void onCreate(Bundle arg0) {
            super.onCreate(arg0);
            setContentView(R.layout.fragment_top_rated);
            fragment = (MainFragment) getSupportFragmentManager().findFragmentById(R.id.main_fragment);
    }
    public void onButtonClicked(){
          // handle button clicked
        Toast.makeText(getApplicationContext(), "helo from", Toast.LENGTH_SHORT).show();
    }
}