Error on cast? Opening a dialogfragment from fragment

Question

I'm getting this error when I trying to open a timepicker or datepicker from a fragment. I know that it is a context problem, but I don't know how to solve it.

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)

SOURCE CODE

AgendaActivity.java <-- Main

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();

The problem is that your Activity does not implement TimePickerFragmentListener. You implement it in your NewEventFragment, so you could alternatively start your dialog this way:

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

and access the parent fragment with getTargetFragment:

TimePickerFragmentListener listener = (TimePickerFragmentListener) getTargetFragment();