鑄造錯誤？從片段打開對話框片段

Question

我在嘗試從片段中打開timepicker或datepicker時出現此錯誤。我知道這是一個背景問題，但我不知道如何解決它。

05-11 13:56:12.026 18397-18397/com.victor.martin.agenda.app E/AndroidRuntime﹕ FATAL EXCEPTION: main 
    java.lang.ClassCastException: com.victor.martin.agenda.app.AgendaActivity cannot be cast to com.victor.martin.agenda.app.TimePickerFragment$TimePickerFragmentListener 
      at com.victor.martin.agenda.app.TimePickerFragment.onTimeSet(TimePickerFragment.java:39) 
      at android.app.TimePickerDialog.tryNotifyTimeSet(TimePickerDialog.java) 
      at android.app.TimePickerDialog.onClick(TimePickerDialog.java) 
      at com.android.internal.app.AlertController$ButtonHandler.handleMessage(AlertController.java) 
      at android.os.Handler.dispatchMessage(Handler.java) 
      at android.os.Looper.loop(Looper.java) 
      at android.app.ActivityThread.main(ActivityThread.java) 
      at java.lang.reflect.Method.invokeNative(Native Method) 
      at java.lang.reflect.Method.invoke(Method.java) 
      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java) 
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java) 
      at de.robv.android.xposed.XposedBridge.main(XposedBridge.java:133) 
      at dalvik.system.NativeStart.main(Native Method) 

源代碼

AgendaActivity.java < - 主要

package com.victor.martin.agenda.app; 

import android.os.Bundle; 
import android.support.v4.app.Fragment; 
import android.support.v4.app.FragmentManager; 
import android.support.v4.app.FragmentPagerAdapter; 
import android.support.v4.app.FragmentTransaction; 
import android.support.v4.view.ViewPager; 
import android.support.v7.app.ActionBar; 
import android.support.v7.app.ActionBarActivity; 
import android.view.LayoutInflater; 
import android.view.Menu; 
import android.view.MenuItem; 
import android.view.View; 
import android.view.ViewGroup; 

import com.victor.martin.agenda.app.fragments.HistoryFragment; 
import com.victor.martin.agenda.app.fragments.NewEventFragment; 

import java.util.Locale; 


public class AgendaActivity extends ActionBarActivity implements ActionBar.TabListener { 

    /** 
    * The {@link android.support.v4.view.PagerAdapter} that will provide 
    * fragments for each of the sections. We use a 
    * {@link FragmentPagerAdapter} derivative, which will keep every 
    * loaded fragment in memory. If this becomes too memory intensive, it 
    * may be best to switch to a 
    * {@link android.support.v4.app.FragmentStatePagerAdapter}. 
    */ 
    SectionsPagerAdapter mSectionsPagerAdapter; 

    /** 
    * The {@link ViewPager} that will host the section contents. 
    */ 
    ViewPager mViewPager; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_agenda); 

     // Set up the action bar. 
     final ActionBar actionBar = getSupportActionBar(); 
     actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS); 

     // Create the adapter that will return a fragment for each of the three 
     // primary sections of the activity. 
     mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager()); 

     // Set up the ViewPager with the sections adapter. 
     mViewPager = (ViewPager) findViewById(R.id.pager); 
     mViewPager.setAdapter(mSectionsPagerAdapter); 

     // When swiping between different sections, select the corresponding 
     // tab. We can also use ActionBar.Tab#select() to do this if we have 
     // a reference to the Tab. 
     mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() { 
      @Override 
      public void onPageSelected(int position) { 
       actionBar.setSelectedNavigationItem(position); 
      } 
     }); 

     // For each of the sections in the app, add a tab to the action bar. 
     for (int i = 0; i < mSectionsPagerAdapter.getCount(); i++) { 
      // Create a tab with text corresponding to the page title defined by 
      // the adapter. Also specify this Activity object, which implements 
      // the TabListener interface, as the callback (listener) for when 
      // this tab is selected. 
      actionBar.addTab(
        actionBar.newTab() 
          .setText(mSectionsPagerAdapter.getPageTitle(i)) 
          .setTabListener(this)); 
     } 
    } 


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

    @Override 
    public boolean onOptionsItemSelected(MenuItem item) { 
     // Handle action bar item clicks here. The action bar will 
     // automatically handle clicks on the Home/Up button, so long 
     // as you specify a parent activity in AndroidManifest.xml. 
     int id = item.getItemId(); 
     if (id == R.id.action_settings) { 
      return true; 
     } 
     return super.onOptionsItemSelected(item); 
    } 

    @Override 
    public void onTabSelected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) { 
     // When the given tab is selected, switch to the corresponding page in 
     // the ViewPager. 
     mViewPager.setCurrentItem(tab.getPosition()); 
    } 

    @Override 
    public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) { 
    } 

    @Override 
    public void onTabReselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) { 
    } 

    /** 
    * A {@link FragmentPagerAdapter} that returns a fragment corresponding to 
    * one of the sections/tabs/pages. 
    */ 
    public class SectionsPagerAdapter extends FragmentPagerAdapter { 

     public SectionsPagerAdapter(FragmentManager fm) { 
      super(fm); 
     } 

     @Override 
     public Fragment getItem(int position) { 
      // getItem is called to instantiate the fragment for the given page. 
      // Return a PlaceholderFragment (defined as a static inner class below). 
      switch(position) { 

       case 0: return HistoryFragment.newInstance("History" + position + 1); 
       case 1: return NewEventFragment.newInstance("New Event" + position + 1); 

       default: return HistoryFragment.newInstance("History, Default" + position + 1); 
      } 
     } 

     @Override 
     public int getCount() { 
      // Show 2 total pages. 
      return 2; 
     } 

     @Override 
     public CharSequence getPageTitle(int position) { 
      Locale l = Locale.getDefault(); 
      switch (position) { 
       case 0: 
        return getString(R.string.str_history).toUpperCase(l); 
       case 1: 
        return getString(R.string.str_new_event).toUpperCase(l); 
       //case 2: 
       // return getString(R.string.title_section3).toUpperCase(l); 
      } 
      return null; 
     } 
    } 

    /** 
    * A placeholder fragment containing a simple view. 
    */ 
    public static class PlaceholderFragment extends Fragment { 
     /** 
     * The fragment argument representing the section number for this 
     * fragment. 
     */ 
     private static final String ARG_SECTION_NUMBER = "section_number"; 

     /** 
     * Returns a new instance of this fragment for the given section 
     * number. 
     */ 
     public static PlaceholderFragment newInstance(int sectionNumber) { 
      PlaceholderFragment fragment = new PlaceholderFragment(); 
      Bundle args = new Bundle(); 
      args.putInt(ARG_SECTION_NUMBER, sectionNumber); 
      fragment.setArguments(args); 
      return fragment; 
     } 

     public PlaceholderFragment() { 
     } 


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



} 

NewEventFragment.java

package com.victor.martin.agenda.app.fragments; 

import android.content.Context; 
import android.os.Bundle; 
import android.support.v4.app.Fragment; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.Button; 
import android.widget.EditText; 

import com.victor.martin.agenda.app.DatePickerFragment; 
import com.victor.martin.agenda.app.R; 
import com.victor.martin.agenda.app.TimePickerFragment; 

/** 
* Created by McFly on 11/05/2014. 
*/ 
public class NewEventFragment extends Fragment implements TimePickerFragment.TimePickerFragmentListener,DatePickerFragment.DatePickerFragmentListener { 

    Button bt_date, bt_time, bt_clear, bt_save; 
    EditText et_description, et_location; 
    Context _c; 

    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 
     View v = inflater.inflate(R.layout.fragment_new_event, container, false); 

     _c = getActivity(); 

     bt_date = (Button)v.findViewById(R.id.bt_date); 
     bt_time = (Button)v.findViewById(R.id.bt_date); 
     bt_clear = (Button)v.findViewById(R.id.bt_clear); 
     bt_save = (Button)v.findViewById(R.id.bt_save); 
     et_description = (EditText)v.findViewById(R.id.et_description); 
     et_location = (EditText)v.findViewById(R.id.et_location); 

     bt_date.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
       showDatePickerDialog(); 
      } 
     }); 

     bt_time.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
       showTimePickerDialog(); 
      } 
     }); 

     return v; 
    } 

    public static NewEventFragment newInstance(String text) { 

     NewEventFragment f = new NewEventFragment(); 
     Bundle b = new Bundle(); 
     b.putString("msg", text); 

     f.setArguments(b); 

     return f; 
    } 

    // Methods 

    //Llamado cuando el usuario pulsa el botón de TimePicker 
    public void showTimePickerDialog() { 
     TimePickerFragment newFragment = new TimePickerFragment(); 
     newFragment.show(this.getFragmentManager(), "timePicker"); 
    } 

    //Llamado cuando el usuario pulsa el botón de DatePicker 
    public void showDatePickerDialog() { 
     DatePickerFragment newFragment = new DatePickerFragment(); 
     newFragment.show(this.getFragmentManager(), "datePicker"); 
    } 

    //Llamado cuando el usuario acaba la selección y los datos son enviados a la actividad 
    @Override 
    public void onFinishTimePickerDialog(int hourOfDay, int minute) { 
     // TODO Auto-generated method stub 
     //Toast.makeText(this, "Hora: " + hourOfDay + minute, Toast.LENGTH_SHORT).show(); 
     bt_time.setText(hourOfDay + ":" + minute); 
    } 

    //Llamado cuando el usuario acaba la selección y los datos son enviados a la actividad 
    @Override 
    public void onFinishDatePickerDialog(int year, int month, int day) { 
     // TODO Auto-generated method stub 
     //Toast.makeText(this, "Fecha: " + year + month + day, Toast.LENGTH_SHORT).show(); 
     bt_date.setText(day + "/" + month + "/" + year); 
    } 
} 

TimePickerFragment.java

package com.victor.martin.agenda.app; 

import android.app.Dialog; 
import android.app.TimePickerDialog; 
import android.os.Bundle; 
import android.support.v4.app.DialogFragment; 
import android.text.format.DateFormat; 
import android.widget.TimePicker; 

import java.util.Calendar; 

/** 
* Created by McFly on 10/05/2014. 
*/ 
public class TimePickerFragment extends DialogFragment implements TimePickerDialog.OnTimeSetListener { 
    //Interface creada para implementar un método que podamos utilizar como 
    //enlace de la actividad en curso y le enviemos la información 
    //seleccionada por el usuario. 

    public interface TimePickerFragmentListener{ 
     void onFinishTimePickerDialog(int hourOfDay, int minute); 
    } 

    @Override 
    public Dialog onCreateDialog(Bundle savedInstanceState) { 
     //Datos que seleccionara el usuario. 
     final Calendar c = Calendar.getInstance(); 
     int hour = c.get(Calendar.HOUR_OF_DAY); 
     int minute = c.get(Calendar.MINUTE); 

     // Creamos la insntacia del TimePicke para devolverla. 
     return new TimePickerDialog(getActivity(), this, hour, minute, DateFormat.is24HourFormat(getActivity())); 

    } 

    public void onTimeSet(TimePicker view, int hourOfDay, int minute) { 
     // Do something with the time chosen by the user 

     TimePickerFragmentListener activity = (TimePickerFragmentListener) getActivity(); 
     activity.onFinishTimePickerDialog(hourOfDay, minute); 
    } 

} 

Answer 1

TimePickerFragmentListener activity = (TimePickerFragmentListener) getActivity(); 

的問題是，你的活動不實現TimePickerFragmentListener。你在你的NewEventFragment實現它，所以你可以或者啓動對話是這樣的：

public void showTimePickerDialog() { 
    TimePickerFragment newFragment = new TimePickerFragment(); 
    // added request code also 
    newFragment.setTargetFragment(this, 0); 
    newFragment.show(this.getFragmentManager(), "timePicker"); 
} 

與getTargetFragment訪問父片段：

TimePickerFragmentListener listener = (TimePickerFragmentListener) getTargetFragment(); 

Answer 2

Kupsef回答解決了這個問題。