我试图使用片段与一个ViewPager使用FragmentPagerAdapter。 我想要实现的是替换一个片段,位于ViewPager的第一页,与另一个。

寻呼机由两个页面组成。第一个是FirstPagerFragment,第二个是SecondPagerFragment。点击第一页的一个按钮。我想用NextFragment替换FirstPagerFragment。

下面是我的代码。

public class FragmentPagerActivity extends FragmentActivity {

    static final int NUM_ITEMS = 2;

    MyAdapter mAdapter;
    ViewPager mPager;

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

        mAdapter = new MyAdapter(getSupportFragmentManager());

        mPager = (ViewPager) findViewById(R.id.pager);
        mPager.setAdapter(mAdapter);

    }


    /**
     * Pager Adapter
     */
    public static class MyAdapter extends FragmentPagerAdapter {
        public MyAdapter(FragmentManager fm) {
            super(fm);
        }

        @Override
        public int getCount() {
            return NUM_ITEMS;
        }

        @Override
        public Fragment getItem(int position) {

            if(position == 0) {
                return FirstPageFragment.newInstance();
            } else {
                return SecondPageFragment.newInstance();
            }

        }
    }


    /**
     * Second Page FRAGMENT
     */
    public static class SecondPageFragment extends Fragment {

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

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
            //Log.d("DEBUG", "onCreateView");
            return inflater.inflate(R.layout.second, container, false);

        }
    }

    /**
     * FIRST PAGE FRAGMENT
     */
    public static class FirstPageFragment extends Fragment {

        Button button;

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

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
            //Log.d("DEBUG", "onCreateView");
            View root = inflater.inflate(R.layout.first, container, false);
            button = (Button) root.findViewById(R.id.button);
            button.setOnClickListener(new OnClickListener() {

                @Override
                public void onClick(View v) {
                    FragmentTransaction trans = getFragmentManager().beginTransaction();
                                    trans.replace(R.id.first_fragment_root_id, NextFragment.newInstance());
                    trans.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
                    trans.addToBackStack(null);
                    trans.commit();

                }

            });

            return root;
        }

        /**
     * Next Page FRAGMENT in the First Page
     */
    public static class NextFragment extends Fragment {

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

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
            //Log.d("DEBUG", "onCreateView");
            return inflater.inflate(R.layout.next, container, false);

        }
    }
}

...这里是XML文件

fragment_pager.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:orientation="vertical" android:padding="4dip"
        android:gravity="center_horizontal"
        android:layout_width="match_parent" android:layout_height="match_parent">

    <android.support.v4.view.ViewPager
            android:id="@+id/pager"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_weight="1">
    </android.support.v4.view.ViewPager>

</LinearLayout>

first.xml

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

  <Button android:id="@+id/button"
     android:layout_width="wrap_content" android:layout_height="wrap_content"
     android:text="to next"/>

</LinearLayout>

现在的问题是……我应该使用哪个ID

trans.replace(R.id.first_fragment_root_id, NextFragment.newInstance());

?

如果我用r。id。first_fragment_root_id,替换工作,但Hierarchy Viewer显示一个奇怪的行为,如下所示。

一开始的情况是

更换后的情况是

正如你所看到的,有一些错误,我希望在替换片段后找到与第一张图片中相同的状态。


当前回答

这就是我实现目标的方法。

首先,在viewPager标签中添加Root_fragment,你想在其中实现按钮点击片段事件。例子;

@Override
public Fragment getItem(int position) {
  if(position==0)
      return RootTabFragment.newInstance();
  else
      return SecondPagerFragment.newInstance();
}

首先,RootTabFragment应该包含FragmentLayout来改变片段。

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
   xmlns:tools="http://schemas.android.com/tools"
   android:id="@+id/root_frame"
   android:layout_width="match_parent"
   android:layout_height="match_parent">
</FrameLayout>

然后,在RootTabFragment onCreateView内部,实现FirstPagerFragment的fragmentChange

getChildFragmentManager().beginTransaction().replace(R.id.root_frame, FirstPagerFragment.newInstance()).commit();

在那之后,实现onClick事件为您的按钮在FirstPagerFragment和使片段改变像那样再次。

getChildFragmentManager().beginTransaction().replace(R.id.root_frame, NextFragment.newInstance()).commit();

希望这对你们有帮助。

其他回答

Here's my relatively simple solution to this problem. The keys to this solution are to use FragmentStatePagerAdapter instead of FragmentPagerAdapter as the former will remove unused fragments for you while the later still retains their instances. The second is the use of POSITION_NONE in getItem(). I've used a simple List to keep track of my fragments. My requirement was to replace the entire list of fragments at once with a new list, but the below could be easily modified to replace individual fragments:

public class MyFragmentAdapter extends FragmentStatePagerAdapter {
    private List<Fragment> fragmentList = new ArrayList<Fragment>();
    private List<String> tabTitleList = new ArrayList<String>();

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

    public void addFragments(List<Fragment> fragments, List<String> titles) {
        fragmentList.clear();
        tabTitleList.clear();
        fragmentList.addAll(fragments);
        tabTitleList.addAll(titles);
        notifyDataSetChanged();
    }

    @Override
    public int getItemPosition(Object object) {
        if (fragmentList.contains(object)) {
            return POSITION_UNCHANGED;
        }
        return POSITION_NONE;
    }

    @Override
    public Fragment getItem(int item) {
        if (item >= fragmentList.size()) {
            return null;
        }
        return fragmentList.get(item);
    }

    @Override
    public int getCount() {
        return fragmentList.size();
    }

    @Override
    public CharSequence getPageTitle(int position) {
        return tabTitleList.get(position);
    }
}

从2012年11月13日起,在ViewPager中重新调整片段似乎变得容易多了。谷歌发布的Android 4.2支持嵌套片段,在新的Android支持库v11中也支持它,所以这将一直工作到1.6

It's very similiar to the normal way of replacing a fragment except you use getChildFragmentManager. It seems to work except the nested fragment backstack isn't popped when the user clicks the back button. As per the solution in that linked question, you need to manually call the popBackStackImmediate() on the child manager of the fragment. So you need to override onBackPressed() of the ViewPager activity where you'll get the current fragment of the ViewPager and call getChildFragmentManager().popBackStackImmediate() on it.

获取当前正在显示的片段也有点棘手,我使用了这个肮脏的“android:switcher:VIEWPAGER_ID:INDEX”解决方案,但你也可以跟踪ViewPager的所有片段,正如本页上第二个解决方案所解释的那样。

这是我的代码,当用户单击一行时,ViewPager会显示一个详细的视图,后退按钮工作。为了简洁起见,我尝试只包括相关代码,所以如果你想要完整的应用程序上传到GitHub,请留下评论。

HomeActivity.java

 public class HomeActivity extends SherlockFragmentActivity {
FragmentAdapter mAdapter;
ViewPager mPager;
TabPageIndicator mIndicator;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    mAdapter = new FragmentAdapter(getSupportFragmentManager());
    mPager = (ViewPager)findViewById(R.id.pager);
    mPager.setAdapter(mAdapter);
    mIndicator = (TabPageIndicator)findViewById(R.id.indicator);
    mIndicator.setViewPager(mPager);
}

// This the important bit to make sure the back button works when you're nesting fragments. Very hacky, all it takes is some Google engineer to change that ViewPager view tag to break this in a future Android update.
@Override
public void onBackPressed() {
    Fragment fragment = (Fragment) getSupportFragmentManager().findFragmentByTag("android:switcher:" + R.id.pager + ":"+mPager.getCurrentItem());
    if (fragment != null) // could be null if not instantiated yet
    {
        if (fragment.getView() != null) {
            // Pop the backstack on the ChildManager if there is any. If not, close this activity as normal.
            if (!fragment.getChildFragmentManager().popBackStackImmediate()) {
                finish();
            }
        }
    }
}

class FragmentAdapter extends FragmentPagerAdapter {        
    public FragmentAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int position) {
        switch (position) {
        case 0:
            return ListProductsFragment.newInstance();
        case 1:
            return ListActiveSubstancesFragment.newInstance();
        case 2:
            return ListProductFunctionsFragment.newInstance();
        case 3:
            return ListCropsFragment.newInstance();
        default:
            return null;
        }
    }

    @Override
    public int getCount() {
        return 4;
    }

 }
}

ListProductsFragment.java

public class ListProductsFragment extends SherlockFragment {
private ListView list;

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

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View V = inflater.inflate(R.layout.list, container, false);
    list = (ListView)V.findViewById(android.R.id.list);
    list.setOnItemClickListener(new OnItemClickListener() {
        public void onItemClick(AdapterView<?> parent, View view,
            int position, long id) {
          // This is important bit
          Fragment productDetailFragment = FragmentProductDetail.newInstance();
          FragmentTransaction transaction = getChildFragmentManager().beginTransaction();
          transaction.addToBackStack(null);
          transaction.replace(R.id.products_list_linear, productDetailFragment).commit();
        }
      });       
    return V;
}
}

我找到了一个简单的解决方案,即使你想在中间添加新的片段或替换当前片段,它也能很好地工作。在我的解决方案中,您应该重写getItemId(),它应该为每个片段返回唯一的id。不是默认的位置。

就是这样:

public class DynamicPagerAdapter extends FragmentPagerAdapter {

private ArrayList<Page> mPages = new ArrayList<Page>();
private ArrayList<Fragment> mFragments = new ArrayList<Fragment>();

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

public void replacePage(int position, Page page) {
    mPages.set(position, page);
    notifyDataSetChanged();
}

public void setPages(ArrayList<Page> pages) {
    mPages = pages;
    notifyDataSetChanged();
}

@Override
public Fragment getItem(int position) {
    if (mPages.get(position).mPageType == PageType.FIRST) {
        return FirstFragment.newInstance(mPages.get(position));
    } else {
        return SecondFragment.newInstance(mPages.get(position));
    }
}

@Override
public int getCount() {
    return mPages.size();
}

@Override
public long getItemId(int position) {
    // return unique id
    return mPages.get(position).getId();
}

@Override
public Object instantiateItem(ViewGroup container, int position) {
    Fragment fragment = (Fragment) super.instantiateItem(container, position);
    while (mFragments.size() <= position) {
        mFragments.add(null);
    }
    mFragments.set(position, fragment);
    return fragment;
}

@Override
public void destroyItem(ViewGroup container, int position, Object object) {
    super.destroyItem(container, position, object);
    mFragments.set(position, null);
}

@Override
public int getItemPosition(Object object) {
    PagerFragment pagerFragment = (PagerFragment) object;
    Page page = pagerFragment.getPage();
    int position = mFragments.indexOf(pagerFragment);
    if (page.equals(mPages.get(position))) {
        return POSITION_UNCHANGED;
    } else {
        return POSITION_NONE;
    }
}
}

注意:在这个例子中,FirstFragment和SecondFragment扩展了抽象类PageFragment,它有方法getPage()。

基于@wize的回答,我发现它很有用,也很优雅,我可以部分实现我想要的,因为我想要电缆在被替换后回到第一个片段。我稍微修改了一下他的代码就实现了。

这将是FragmentPagerAdapter:

public static class MyAdapter extends FragmentPagerAdapter {
    private final class CalendarPageListener implements
            CalendarPageFragmentListener {
        public void onSwitchToNextFragment() {
            mFragmentManager.beginTransaction().remove(mFragmentAtPos0)
                    .commit();
            if (mFragmentAtPos0 instanceof FirstFragment){
                mFragmentAtPos0 = NextFragment.newInstance(listener);
            }else{ // Instance of NextFragment
                mFragmentAtPos0 = FirstFragment.newInstance(listener);
            }
            notifyDataSetChanged();
        }
    }

    CalendarPageListener listener = new CalendarPageListener();;
    private Fragment mFragmentAtPos0;
    private FragmentManager mFragmentManager;

    public MyAdapter(FragmentManager fm) {
        super(fm);
        mFragmentManager = fm;
    }

    @Override
    public int getCount() {
        return NUM_ITEMS;
    }

    @Override
    public int getItemPosition(Object object) {
        if (object instanceof FirstFragment && mFragmentAtPos0 instanceof NextFragment)
            return POSITION_NONE;
        if (object instanceof NextFragment && mFragmentAtPos0 instanceof FirstFragment)
            return POSITION_NONE;
        return POSITION_UNCHANGED;
    }

    @Override
    public Fragment getItem(int position) {
        if (position == 0)
            return Portada.newInstance();
        if (position == 1) { // Position where you want to replace fragments
            if (mFragmentAtPos0 == null) {
                mFragmentAtPos0 = FirstFragment.newInstance(listener);
            }
            return mFragmentAtPos0;
        }
        if (position == 2)
            return Clasificacion.newInstance();
        if (position == 3)
            return Informacion.newInstance();

        return null;
    }
}

public interface CalendarPageFragmentListener {
    void onSwitchToNextFragment();
}

要执行替换,只需定义一个静态字段,类型为CalendarPageFragmentListener,并通过相应片段的newInstance方法初始化,并分别调用firstfragment . pagelister . onswitchtonextfragment()或nextfragment . pagelister . onswitchtonextfragment()。

这就是我实现目标的方法。

首先,在viewPager标签中添加Root_fragment,你想在其中实现按钮点击片段事件。例子;

@Override
public Fragment getItem(int position) {
  if(position==0)
      return RootTabFragment.newInstance();
  else
      return SecondPagerFragment.newInstance();
}

首先,RootTabFragment应该包含FragmentLayout来改变片段。

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
   xmlns:tools="http://schemas.android.com/tools"
   android:id="@+id/root_frame"
   android:layout_width="match_parent"
   android:layout_height="match_parent">
</FrameLayout>

然后,在RootTabFragment onCreateView内部,实现FirstPagerFragment的fragmentChange

getChildFragmentManager().beginTransaction().replace(R.id.root_frame, FirstPagerFragment.newInstance()).commit();

在那之后,实现onClick事件为您的按钮在FirstPagerFragment和使片段改变像那样再次。

getChildFragmentManager().beginTransaction().replace(R.id.root_frame, NextFragment.newInstance()).commit();

希望这对你们有帮助。