Incompatible types: Fragment cannot be converted to NavigationDrawerFragment

问题

I've been working on an app using API 14, but I had to downgrade to API 10. the app has fragments and activity fragments, I have imported the libraries and used the getFragmentSupportManager because it is v4. However, I have following error:

I created a dummy app with Drawer layout and fragments with API 10 from the beginning, it had the same line in MyActivity file and it was not an error. Here is my code:

package az.test2;

import android.app.Activity;
import android.os.Bundle;
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.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.view.Gravity;


public class MyActivity extends ActionBarActivity
    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_my);

        mNavigationDrawerFragment = (NavigationDrawerFragment)
           getSupportFragmentManager().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
        android.support.v4.app.FragmentManager lolo;

        FragmentManager FM = getSupportFragmentManager();
        FragAV fav = new FragAV();
        FragW fw = new FragW();

        switch (position){
            case 0:
                FM.beginTransaction()
                    .replace(R.id.container, fav).commit();
                break;
            case 1:
                FM.beginTransaction()
                    .replace(R.id.container, fw).commit();
                break;
            case 2: break;
        }


        //FM.beginTransaction().replace(R.id.container, PlaceholderFragment.newInstance(position + 1)).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 = getSupportActionBar();
        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.my, 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();
        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_my, container, false);
            return rootView;
        }

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

I did everything I could but this error seems to be very rare. any help would be much appreciated.

回答1:

When using the support pack, your fragments should extend android.support.v4.app.Fragment and not the regular Fragment class.

回答2:

make sure your drawer fragment class extend android.support.v4.app.Fragment not fragment.

回答3:

change this

NavigationDrawerFragment mNavigationDrawerFragment;
mNavigationDrawerFragment = (NavigationDrawerFragment)
getSupportFragmentManager().findFragmentById(R.id.navigation_drawer);

to

Fragment mNavigationDrawerFragment;
mNavigationDrawerFragment = (NavigationDrawerFragment)
getSupportFragmentManager().findFragmentById(R.id.navigation_drawer);

回答4:

in your mNavigationDrawerFragment class import "import android.support.v4.app.Fragment;" instead of "import android.app.Fragment;"

来源：https://stackoverflow.com/questions/26386320/incompatible-types-fragment-cannot-be-converted-to-navigationdrawerfragment