不兼容类型：无法将Fragment转换为NavigationDrawerFragment

Question

我一直在使用API 14开发一个应用程序，但是我不得不降级到API 10。该应用程序具有片段和活动片段，我已经导入了库并使用了getFragmentSupportManager，因为它是v4。然而，我遇到了以下错误：

我从头开始创建了一个带有API 10的抽屉布局和片段的虚拟应用程序，它在MyActivity文件中有相同的行，但没有错误。这是我的代码：

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));
        }
    }
}

我尽力了，但这个错误似乎非常罕见。任何帮助都将不胜感激。

- Med Zamrik

---

我遇到了同样的问题。这个 stack-overflow 答案 解决了我的问题。 - Nadeesha Thilakarathne

Answer 1

在使用支持包时，您的片段应该扩展 android.support.v4.app.Fragment 而不是常规 Fragment 类。

- zmbq

---

在编程中，这段内容需要翻译成中文：它是在“import”部分。每次调用类时都要使用整行吗？ - Med Zamrik

不，只要确保您的NavigationDrawerFragment类继承它即可。你可能没有在它的声明中导入它。 - zmbq

请原谅我，我是Android开发的新手，我不太明白您所说的“extends it”的意思。 - Med Zamrik

这是他的意思，例如这段代码是你自己的：PlaceholderFragment扩展（Fragment），他的意思是确保该片段扩展了支持库的片段@EdZamrik - Elltz

我做了这个 private class NavigationDrawerFragment extends Fragment{} 然后 private NavigationDrawerFragment mNavigationDrawerFragment; 但是在 mNavigationDrawerFragment.setUp 那行，它说无法解决 setUp() 方法。我认为它现在将其视为一个片段而不是 NavigationDrawerFragment。我做对了吗？ @Elltz @zmbq - Med Zamrik

在包含此行的文件中，您是否有正确的使用行（带有android.support）？ - zmbq

Answer 2

请确保您的抽屉Fragment类扩展自android.support.v4.app.Fragment而不是Fragment。

- Setmax

Answer 3

改变这个

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

到

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

- Elltz

---

然后尝试Zmbq的方法，从正确的包中扩展片段。 - Elltz

Answer 4

在你的mNavigationDrawerFragment类中，导入“import android.support.v4.app.Fragment;”，而不是“import android.app.Fragment;”。

- user2035257