Android导航抽屉中的片段错误

Question

您好，我多次遇到表达式预期错误，而且我不知道我在做什么错，如果有人可以帮助我，那会很棒。 谢谢。

import android.support.v4.app.Fragment;
import android.app.Activity;
import android.app.ActionBar;
import android.app.FragmentManager;
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
    FragmentManager fragmentManager = getFragmentManager();
    fragmentManager.beginTransaction()
           .replace(R.id.container, Fragment) //expression expected error on "Fragment"
                .commit();
}

public void onSectionAttached(int position) {
    switch (position) {
        case 1:
            Fragment = new Welcome(); //expression expected error on "Fragment"
            break;
        case 2:
            Fragment = new Tutorials(); //expression expected error on "Fragment"
            break;
        case 3:
            Fragment = new Blueprints(); //expression expected error on "Fragment"
            break;
        case 4:
            Fragment = new Wiki(); //expression expected error on "Fragment"
            break;
        case 5:
            Fragment = new Chat(); //expression expected error on "Fragment"
            break;
        case 6:
            Fragment = new Item_Search(); //expression expected error on "Fragment"
            break;
        case 7:
            Fragment = new Recipes(); //expression expected error on "Fragment"
            break;
        case 8:
            Fragment = new Wallpaper(); //expression expected error on "Fragment"
            break;
        case 9:
            Fragment = new Maps_Mods(); //expression expected error on "Fragment"
            break;
        default :
            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();
    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);
        TextView textView = (TextView) rootView.findViewById(R.id.section_label);
        textView.setText(Integer.toString(getArguments().getInt(ARG_SECTION_NUMBER)));
        return rootView;
    }

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

}

该错误强调“片段”。 我正在尝试将导航抽屉缝到不同的片段。

Answer 1

它应该是

fragmentManager.beginTransaction()
       .replace(R.id.container,new Welcome())

和

Welcome fragment = new Welcome(); 

其他人也一样。

由于您正在使用基于支持的片段。 你需要改变这个

public class MainActivity extends Activity

至

public class MainActivity extends ActionBarActivity

如果需要ActionBar 。 您还需要使用AppCompat 。

检查一下

具有Backword兼容android的导航抽屉

Answer 2

片段是一个关键词。 您需要的是Fragment类型的变量。 因此，例如，将其与mTitle放在同一部分：

Fragment mFragment = null; 

在您的switch语句中，例如，输入：

mFragment = new Welcome();

然后，在设置交易时，您可以输入：

fragmentManager.beginTransaction()
   .replace(R.id.container, mFragment)

这可能无法解决您所有的问题，但是应该使您克服这些编译错误。