Changing fragment from Navigation drawer

Question

I am basically having the exact same problem as OP here: How to change fragments using Android navigation drawer

Also using the Template for an navigation drawer activity in Android Studio.

I tried Dreagan's answer, but I am now stuck with a cycle of errors.

Here is my code

import android.app.Activity;
import android.app.ActionBar;
import android.app.Fragment;
import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.content.Context;
import android.os.Build;
import android.os.Bundle;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.support.v4.widget.DrawerLayout;
import android.widget.ArrayAdapter;
import android.widget.TextView;


public   class MainActivity extends Activity
        implements NavigationDrawerFragment.NavigationDrawerCallbacks {

    /**
     * Fragment managing the behaviors, interactions and presentation of the navigation drawer.
     */
    private NavigationDrawerFragment mNavigationDrawerFragment;

    /**
     * Used to store the last screen title. For use in {@link #restoreActionBar()}.
     */
    private CharSequence mTitle;

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

        mNavigationDrawerFragment = (NavigationDrawerFragment)
                getFragmentManager().findFragmentById(R.id.navigation_drawer);
        mTitle = getTitle();

        // Set up the drawer.
        mNavigationDrawerFragment.setUp(
                R.id.navigation_drawer,
                (DrawerLayout) findViewById(R.id.drawer_layout));
    }

    @Override
    public void onNavigationDrawerItemSelected(int position) {
        // update the main content by replacing fragments

        Fragment fragment = new NewsfeedFragment();
        FragmentManager fragmentManager = getFragmentManager();

        Bundle args = new Bundle();
        args.putInt(NewsfeedFragment.ARG_PLANET_NUMBER, position);
        fragment.setArguments(args);

        switch(position){
            case 0:
                fragment = new NewsfeedFragment();

                break;

            case 1:
                fragment = new NewsfeedFragment();
                break;
        }
        fragmentManager.beginTransaction()
                .replace(R.id.container, fragment)
                .commit();
    }

    public void onSectionAttached(int number) {

        switch (number) {
            case 1:
                mTitle = getString(R.string.title_section1);
                break;

            case 2:
                mTitle = getString(R.string.title_section2);
                break;

            case 3:
                mTitle = getString(R.string.title_section3);
                break;
        }
    }

    public void restoreActionBar() {
        ActionBar actionBar = getActionBar();
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_STANDARD);
        actionBar.setDisplayShowTitleEnabled(true);
        actionBar.setTitle(mTitle);
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        if (!mNavigationDrawerFragment.isDrawerOpen()) {
            // Only show items in the action bar relevant to this screen
            // if the drawer is not showing. Otherwise, let the drawer
            // decide what to show in the action bar.
            getMenuInflater().inflate(R.menu.main, menu);
            restoreActionBar();
            return true;
        }
        return super.onCreateOptionsMenu(menu);
    }

    @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();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    /**
     * 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_main, container, false);
            return rootView;
        }

        @Override
        public void onAttach(Activity activity) {
            super.onAttach(activity);
            ((MainActivity) activity).onSectionAttached(
                    getArguments().getInt(ARG_SECTION_NUMBER));
        }
    }

}

If I run the code as it is here I get following error:

java.lang.RuntimeException: Unable to start activity ComponentInfo{dk.gruppe2.jammerbugtevent/dk.gruppe2.jammerbugtevent.MainActivity}: java.lang.ClassCastException: dk.gruppe2.jammerbugtevent.MainActivity@429e4a70 must implement OnFragmentInteractionListener

When I implement OnFragmentInteractionListener, I get the following error:

Error:(22, 9) error: MainActivity is not abstract and does not override abstract method onFragmentInteraction(Uri) in OnFragmentInteractionListener

When i declare MainActivity as abstract, i get this error:

    java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{dk.gruppe2.jammerbugtevent/dk.gruppe2.jammerbugtevent.MainActivity}: java.lang.InstantiationException: can't instantiate class dk.gruppe2.jammerbugtevent.MainActivity

I am very new to android, and not exactly an expert regarding programming to begin with. Any help would be much appreciated. Thanks In advance.

Answer 1

I found that I only implemented the interfaces, but still needed to implement the methods from the interfaces

Answer 2

Here is an explanation of things!

Reading your code i did not see any class cast exception... You are casting your activity to the interface OnFragmentInteractionListener. Maybe in one of the fragments.

Also:

When I implement OnFragmentInteractionListener, I get the following error:

Error:(22, 9) error: MainActivity is not abstract and does not override abstract method onFragmentInteraction(Uri) in OnFragmentInteractionListener

When you implement the OnFragmentInteractionListener you must also Override the method: onFragmentInteraction(Uri).

Answer 3

It looks like you aren't setting the fragment's correctly:

@Override
    public void onNavigationDrawerItemSelected(int position) {
        FragmentManager fragmentManager = getSupportFragmentManager();
        switch(position)
        {
            case 0:
                fragmentManager.beginTransaction()
                        .replace(R.id.container, MainListFragment.newInstance())
                        .commit();
                break;
            case 1:
                fragmentManager.beginTransaction()
                        .replace(R.id.container, Fragment2.newInstance())
                        .commit();
            case 2:
                fragmentManager.beginTransaction()
                        .replace(R.id.container, Fragment3.newInstance())
                        .commit();
                break;
        }

    } 

Try using this format, as it stands, you aren't using the new instance method you've defined in the fragment.