Question

我不熟悉Android开发和Java以外的简单JavaScripts网页。我创建了一个显示三个不同片段的视图寻呼机。对于第二个片段，BooksFragment，我使用网格视图来显示按钮网格，当用户按下时应将BooksFragment替换为另一个视图。

我遇到的问题是，尽管我使用 .replace（）来替换片段，但第二个片段只显示在原始片段之上。现在，我已经广泛搜索了我的问题，我相信通常发生的原因是原始片段未创建动态。作为我的菜鸟，看起来我似乎是动态创建片段，但我可能会弄错（我在任何XML文件中都没有使用任何标签）。有人可以帮帮我吗？我的代码如下：

MainActivity.java

import android.app.ActionBar.Tab;
import android.app.Activity;
import android.app.ActionBar;
import android.support.v4.app.Fragment;
import android.app.FragmentTransaction;
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.os.Build;
import android.support.v4.app.FragmentActivity;
import android.support.v4.view.ViewPager;
import android.support.v4.app.FragmentManager;

public class MainActivity extends FragmentActivity implements
ActionBar.TabListener {

    // strings for tabs
    private ViewPager viewPager;
    private TabsPagerAdapter mAdapter;
    private ActionBar actionBar;
    // tab titles
    private String[] tabs = {"Status",
                            "Schedule",
                            "Books"};



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


        // Initialization
        viewPager = (ViewPager) findViewById(R.id.pager);
        actionBar = getActionBar();
        mAdapter = new TabsPagerAdapter(getSupportFragmentManager());

        viewPager.setAdapter(mAdapter);
        //actionBar.setHomeButtonEnabled(false);
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

        // Adding Tabs
        for (String tab_name : tabs) {
            actionBar.addTab(actionBar.newTab().setText(tab_name).setTabListener(this));
        }

        viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {

            @Override
            public void onPageSelected(int position) {
                // on changing the page
                // make respected tab selected
                actionBar.setSelectedNavigationItem(position);
            }

            @Override
            public void onPageScrolled(int arg0, float arg1, int arg2) {

            }

            @Override
            public void onPageScrollStateChanged(int arg0) {

            }
        });


        if (savedInstanceState == null) {
            getSupportFragmentManager().beginTransaction()
                    .add(R.id.pager, new PlaceholderFragment()).commit();
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {

        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, 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);
    }

    public static class PlaceholderFragment extends 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 onTabSelected(Tab tab, FragmentTransaction ft) {
        // on tab selected
                // show respected fragment view
                viewPager.setCurrentItem(tab.getPosition());

    }

    @Override
    public void onTabUnselected(Tab tab, FragmentTransaction ft) {
        // TODO Auto-generated method stub
    }

    @Override
    public void onTabReselected(Tab tab, FragmentTransaction ft) {
        // TODO Auto-generated method stub
    }
}

TabsPagerAdapter.java

import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;


public class TabsPagerAdapter extends FragmentPagerAdapter{

     public TabsPagerAdapter(FragmentManager fm) {
        super(fm);
     }

     @Override
     public Fragment getItem(int index) {

         switch (index) {
         case 0:
             // First fragment activity
             return new StatusFragment();
         case 1:
             // Second fragment activity
             return new ScheduleFragment();
         case 2:
             // Third fragment activity
             return new BooksFragment();
         }

         return null;
     }

     @Override
     public int getCount() {
         // get item count - equal to number of tabs
         return 3;
     }
}

BooksFragment.java

import java.util.ArrayList;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentTransaction;
import android.view.LayoutInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.GridView;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.AdapterView.OnItemSelectedListener;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;


public class BooksFragment extends Fragment implements OnClickListener {

    // get database data
    private static final String DB_NAME = "bookReadingTracker";
    private static final String TABLE_NAME = "book_names";
    private static final String BOOK_NAME_ID = "_id";
    private static final String BOOKNAME = "bookname";
    private static final String BOOKABBR = "bookabbr";

    private SQLiteDatabase database;
    private ArrayList<String> allbooksabbr;

    private OnItemSelectedListener listener;

    GridView gridView;

    public static BooksFragment newInstance() {
        BooksFragment f = new BooksFragment();
        return f;
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

        ExternalDbOpenHelper dbOpenHelper = new ExternalDbOpenHelper(getActivity(), DB_NAME);
        database = dbOpenHelper.openDataBase();

        fillAllbooksabbr();

        View view = inflater.inflate(R.layout.books_fragment, container, false);

        gridView = (GridView) view.findViewById(R.id.gridviewBooks);

        gridView.setAdapter(new MyAdapter(getActivity(), allbooksabbr));

        gridView.setOnItemClickListener(new OnItemClickListener() {
            public void onItemClick(AdapterView<?> parent, View v,
                    int position, long id) {    


                ///////////////////

                Fragment chapterDetailFragment = ChaptersFragment.newInstance();
                FragmentTransaction transaction = getChildFragmentManager().beginTransaction();
                transaction.addToBackStack(null);
                transaction.replace(R.id.booksFragmentHolder, chapterDetailFragment).commit();

                /////////////////////


            }
        });
        return view;
    }


    private void fillAllbooksabbr() {
        allbooksabbr = new ArrayList<String>();

        Cursor allbooksabbrCursor = database.query(TABLE_NAME, new String[] {BOOK_NAME_ID, BOOKABBR}, 
                                                    null, null, null, null, "CAST (" + BOOK_NAME_ID + " AS INTEGER)");
        allbooksabbrCursor.moveToFirst();
        if(!allbooksabbrCursor.isAfterLast()) {
            do {
                String bookabbr_array = allbooksabbrCursor.getString(1);
                allbooksabbr.add(bookabbr_array);
            } while (allbooksabbrCursor.moveToNext());
        }
        allbooksabbrCursor.close();
    }


    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub

    }
}

MyAdapter.java

import java.util.ArrayList;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;


public class MyAdapter extends BaseAdapter {

    private Context context;
    private ArrayList<String> allbooksabbr;

    public MyAdapter(Context context, ArrayList<String> allbooksabbr) {
        this.context = context;
        this.allbooksabbr = allbooksabbr;
    }
    public View getView(int position, View convertView, ViewGroup parent) {

        View gridView;

        if (convertView == null) {
            LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            gridView = inflater.inflate(R.layout.books_button, null);
        } else {
            gridView = (View) convertView;
        }

        //gridView = new View(context);
        gridView.setBackgroundColor(0xff645C69);
        TextView bookButton = (TextView) gridView.findViewById(R.id.bookbutton);
        bookButton.setText(allbooksabbr.get(position));

        return gridView;
    }

    @Override
    public int getCount() {
        // TODO Auto-generated method stub
        return allbooksabbr.size();
    }

    @Override
    public Object getItem(int position) {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public long getItemId(int position) {
        // TODO Auto-generated method stub
        return 0;
    }
}

以下是我的XML文件：

fragment_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.gclapps.bookreadingscheduletracker.MainActivity$PlaceholderFragment" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" />

</RelativeLayout>

books_fragment.xml

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/booksFragmentHolder"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="10dp" >

    <TextView
        android:id="@+id/textViewBooks"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Books" 
        android:textAppearance="?android:attr/textAppearanceSmall"
        android:textColor="#666666"
        android:paddingTop="10dp"
        android:paddingBottom="5dp" />

     <GridView
         android:id="@+id/gridviewBooks"
         android:layout_width="fill_parent"
         android:layout_height="fill_parent"
         android:columnWidth="60dp"
         android:gravity="center"
         android:numColumns="auto_fit"
         android:stretchMode="columnWidth"
         android:verticalSpacing="2dp"
         android:horizontalSpacing="2dp" >
     </GridView>
</FrameLayout>

请帮我查一下我的BooksFragment视图没有被我的ChaptersFragment视图替换的原因。如果BooksFragment视图确实不是动态创建的，请帮助我这样做。我已经阅读了有关如何操作的文档，但是在使用viewpager的情况下我无法弄清楚如何做到这一点。谢谢！

Answer 1

好的，快速查看代码后，我注意到您在这里使用了getChildFragmentManager()：

FragmentTransaction transaction = getChildFragmentManager().beginTransaction();

getChildFragmentManager()管理当前片段的子片段。因此，当您调用replace()时，它实际上并不会删除显示的BookFragment，因为它不是当前片段的子节点（当前片段是BookFragment）。

通常情况下，要替换片段，我会调用getSupportFragmentManager()来获得正确的经理，但由于您使用的是ViewPager，因此会让事情变得更加困难。您可能需要以某种方式更改gridview项目上的ViewPager适配器，并使用在其ChapterDetailFragment方法中返回getItem()的新适配器。

你可能会做这样的事情：

public class TabsPagerAdapter extends FragmentPagerAdapter{
    private boolean isChapterDetailShowing;
    private int chapter;

    public TabsPagerAdapter(FragmentManager fm) {
       super(fm);
    }

    @Override
    public Fragment getItem(int index) {

        switch (index) {
        case 0:
            // First fragment activity
            return new StatusFragment();
        case 1:
            // Second fragment activity
            return new ScheduleFragment();
         case 2:
             // Third fragment activity
             if (isChapterDetailShowing)
                 return new ChapterDetailFragment();
             else
                 return new BooksFragment();
         }

         return null;
     }

    public void showChapter(int chapter) {
        this.chapter = chapter;
        isChapterDetailShowing = true;
        notifyDataSetChanged();
    }

然后在Activity中创建一个方法，该方法调用适配器上的showChapter（）。这个方法将在BookFragment的GridView onItemClickListener中调用（使用getActivity（）并将其强制转换为MainActivity）。

免责声明：不是100％确定这会起作用

Android在View Pager中替换片段

1 个答案: