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

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()。

其他回答

要替换ViewPager中的片段,你可以将ViewPager、PagerAdapter和FragmentStatePagerAdapter类的源代码移动到你的项目中,并添加以下代码。

分为:viewpage:

public void notifyItemChanged(Object oldItem, Object newItem) {
    if (mItems != null) {
            for (ItemInfo itemInfo : mItems) {
                        if (itemInfo.object.equals(oldItem)) {
                                itemInfo.object = newItem;
                        }
                    }
       }
       invalidate();
    }

FragmentStatePagerAdapter:

public void replaceFragmetns(ViewPager container, Fragment oldFragment, Fragment newFragment) {
       startUpdate(container);

       // remove old fragment

       if (mCurTransaction == null) {
            mCurTransaction = mFragmentManager.beginTransaction();
        }
       int position = getFragmentPosition(oldFragment);
        while (mSavedState.size() <= position) {
            mSavedState.add(null);
        }
        mSavedState.set(position, null);
        mFragments.set(position, null);

        mCurTransaction.remove(oldFragment);

        // add new fragment

        while (mFragments.size() <= position) {
            mFragments.add(null);
        }
        mFragments.set(position, newFragment);
        mCurTransaction.add(container.getId(), newFragment);

       finishUpdate(container);

       // ensure getItem returns newFragemtn after calling handleGetItemInbalidated()
       handleGetItemInbalidated(container, oldFragment, newFragment);

       container.notifyItemChanged(oldFragment, newFragment);
    }

protected abstract void handleGetItemInbalidated(View container, Fragment oldFragment, Fragment newFragment);
protected abstract int  getFragmentPosition(Fragment fragment);

handleGetItemInvalidated()确保下一次调用getItem()后返回newFragment getFragmentPosition()返回片段在适配器中的位置。

现在,替换片段调用

mAdapter.replaceFragmetns(mViewPager, oldFragment, newFragment);

如果你对一个示例项目感兴趣,请向我索取资源。

Works Great with AndroidTeam's solution, however I found that I needed the ability to go back much like FrgmentTransaction.addToBackStack(null) But merely adding this will only cause the Fragment to be replaced without notifying the ViewPager. Combining the provided solution with this minor enhancement will allow you to return to the previous state by merely overriding the activity's onBackPressed() method. The biggest drawback is that it will only go back one at a time which may result in multiple back clicks

private ArrayList<Fragment> bFragments = new ArrayList<Fragment>();
private ArrayList<Integer> bPosition = new ArrayList<Integer>();

public void replaceFragmentsWithBackOut(ViewPager container, Fragment oldFragment, Fragment newFragment) {
    startUpdate(container);

    // remove old fragment

    if (mCurTransaction == null) {
         mCurTransaction = mFragmentManager.beginTransaction();
     }
    int position = getFragmentPosition(oldFragment);
     while (mSavedState.size() <= position) {
         mSavedState.add(null);
     }

     //Add Fragment to Back List
     bFragments.add(oldFragment);

     //Add Pager Position to Back List
     bPosition.add(position);

     mSavedState.set(position, null);
     mFragments.set(position, null);

     mCurTransaction.remove(oldFragment);

     // add new fragment

     while (mFragments.size() <= position) {
         mFragments.add(null);
     }
     mFragments.set(position, newFragment);
     mCurTransaction.add(container.getId(), newFragment);

    finishUpdate(container);

    // ensure getItem returns newFragemtn after calling handleGetItemInbalidated()
    handleGetItemInvalidated(container, oldFragment, newFragment);

    container.notifyItemChanged(oldFragment, newFragment);
 }


public boolean popBackImmediate(ViewPager container){
    int bFragSize = bFragments.size();
    int bPosSize = bPosition.size();

    if(bFragSize>0 && bPosSize>0){
        if(bFragSize==bPosSize){
            int last = bFragSize-1;
            int position = bPosition.get(last);

            //Returns Fragment Currently at this position
            Fragment replacedFragment = mFragments.get(position);               
            Fragment originalFragment = bFragments.get(last);

            this.replaceFragments(container, replacedFragment, originalFragment);

            bPosition.remove(last);
            bFragments.remove(last);

            return true;
        }
    }

    return false;       
}

希望这能帮助到一些人。

同样,就getFragmentPosition()而言,它几乎是反向的getItem()。你知道哪些片段去哪里,只是确保你返回正确的位置它将在。这里有一个例子:

    @Override
    protected int getFragmentPosition(Fragment fragment) {
            if(fragment.equals(originalFragment1)){
                return 0;
            }
            if(fragment.equals(replacementFragment1)){
                return 0;
            }
            if(fragment.equals(Fragment2)){
                return 1;
            }
        return -1;
    }

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;
}
}

tl;dr:使用一个主机片段,负责替换其托管内容,并跟踪回溯导航历史(如在浏览器中)。

由于您的用例由固定数量的选项卡组成,我的解决方案工作得很好:想法是用自定义类HostFragment的实例填充ViewPager,这能够替换其托管内容并保持自己的回溯导航历史。要替换托管的片段,你需要调用hostfragment.replaceFragment()方法:

public void replaceFragment(Fragment fragment, boolean addToBackstack) {
    if (addToBackstack) {
        getChildFragmentManager().beginTransaction().replace(R.id.hosted_fragment, fragment).addToBackStack(null).commit();
    } else {
        getChildFragmentManager().beginTransaction().replace(R.id.hosted_fragment, fragment).commit();
    }
}

该方法所做的就是用id R.id替换框架布局。Hosted_fragment和提供给方法的片段。

查看我关于这个主题的教程,了解更多细节和GitHub上完整的工作示例!

我已经实现了一个解决方案:

标签内的动态片段替换 维护每个选项卡的历史记录 处理方向变化

实现这一目标的技巧如下:

使用notifyDataSetChanged()方法来应用片段替换 片段管理器只用于后台,而不用于片段替换 使用纪念品模式(堆栈)维护历史记录

适配器代码如下:

public class TabsAdapter extends FragmentStatePagerAdapter implements ActionBar.TabListener, ViewPager.OnPageChangeListener {

/** The sherlock fragment activity. */
private final SherlockFragmentActivity mActivity;

/** The action bar. */
private final ActionBar mActionBar;

/** The pager. */
private final ViewPager mPager;

/** The tabs. */
private List<TabInfo> mTabs = new LinkedList<TabInfo>();

/** The total number of tabs. */
private int TOTAL_TABS;

private Map<Integer, Stack<TabInfo>> history = new HashMap<Integer, Stack<TabInfo>>();

/**
 * Creates a new instance.
 *
 * @param activity the activity
 * @param pager    the pager
 */
public TabsAdapter(SherlockFragmentActivity activity, ViewPager pager) {
    super(activity.getSupportFragmentManager());
    activity.getSupportFragmentManager();
    this.mActivity = activity;
    this.mActionBar = activity.getSupportActionBar();
    this.mPager = pager;
    mActionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
}

/**
 * Adds the tab.
 *
 * @param image         the image
 * @param fragmentClass the class
 * @param args          the arguments
 */
public void addTab(final Drawable image, final Class fragmentClass, final Bundle args) {
    final TabInfo tabInfo = new TabInfo(fragmentClass, args);
    final ActionBar.Tab tab = mActionBar.newTab();
    tab.setTabListener(this);
    tab.setTag(tabInfo);
    tab.setIcon(image);

    mTabs.add(tabInfo);
    mActionBar.addTab(tab);

    notifyDataSetChanged();
}

@Override
public Fragment getItem(final int position) {
    final TabInfo tabInfo = mTabs.get(position);
    return Fragment.instantiate(mActivity, tabInfo.fragmentClass.getName(), tabInfo.args);
}

@Override
public int getItemPosition(final Object object) {
    /* Get the current position. */
    int position = mActionBar.getSelectedTab().getPosition();

    /* The default value. */
    int pos = POSITION_NONE;
    if (history.get(position).isEmpty()) {
        return POSITION_NONE;
    }

    /* Checks if the object exists in current history. */
    for (Stack<TabInfo> stack : history.values()) {
        TabInfo c = stack.peek();
        if (c.fragmentClass.getName().equals(object.getClass().getName())) {
            pos = POSITION_UNCHANGED;
            break;
        }
    }
    return pos;
}

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

@Override
public void onPageScrollStateChanged(int arg0) {
}

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

@Override
public void onPageSelected(int position) {
    mActionBar.setSelectedNavigationItem(position);
}

@Override
public void onTabSelected(final ActionBar.Tab tab, final FragmentTransaction ft) {
    TabInfo tabInfo = (TabInfo) tab.getTag();
    for (int i = 0; i < mTabs.size(); i++) {
        if (mTabs.get(i).equals(tabInfo)) {
            mPager.setCurrentItem(i);
        }
    }
}

@Override
public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction ft) {
}

@Override
public void onTabReselected(ActionBar.Tab tab, FragmentTransaction ft) {
}

public void replace(final int position, final Class fragmentClass, final Bundle args) {
    /* Save the fragment to the history. */
    mActivity.getSupportFragmentManager().beginTransaction().addToBackStack(null).commit();

    /* Update the tabs. */
    updateTabs(new TabInfo(fragmentClass, args), position);

    /* Updates the history. */
    history.get(position).push(new TabInfo(mTabs.get(position).fragmentClass, mTabs.get(position).args));

    notifyDataSetChanged();
}

/**
 * Updates the tabs.
 *
 * @param tabInfo
 *          the new tab info
 * @param position
 *          the position
 */
private void updateTabs(final TabInfo tabInfo, final int position) {
    mTabs.remove(position);
    mTabs.add(position, tabInfo);
    mActionBar.getTabAt(position).setTag(tabInfo);
}

/**
 * Creates the history using the current state.
 */
public void createHistory() {
    int position = 0;
    TOTAL_TABS = mTabs.size();
    for (TabInfo mTab : mTabs) {
        if (history.get(position) == null) {
            history.put(position, new Stack<TabInfo>());
        }
        history.get(position).push(new TabInfo(mTab.fragmentClass, mTab.args));
        position++;
    }
}

/**
 * Called on back
 */
public void back() {
    int position = mActionBar.getSelectedTab().getPosition();
    if (!historyIsEmpty(position)) {
        /* In case there is not any other item in the history, then finalize the activity. */
        if (isLastItemInHistory(position)) {
            mActivity.finish();
        }
        final TabInfo currentTabInfo = getPrevious(position);
        mTabs.clear();
        for (int i = 0; i < TOTAL_TABS; i++) {
            if (i == position) {
                mTabs.add(new TabInfo(currentTabInfo.fragmentClass, currentTabInfo.args));
            } else {
                TabInfo otherTabInfo = history.get(i).peek();
                mTabs.add(new TabInfo(otherTabInfo.fragmentClass, otherTabInfo.args));
            }
        }
    }
    mActionBar.selectTab(mActionBar.getTabAt(position));
    notifyDataSetChanged();
}

/**
 * Returns if the history is empty.
 *
 * @param position
 *          the position
 * @return  the flag if empty
 */
private boolean historyIsEmpty(final int position) {
    return history == null || history.isEmpty() || history.get(position).isEmpty();
}

private boolean isLastItemInHistory(final int position) {
    return history.get(position).size() == 1;
}

/**
 * Returns the previous state by the position provided.
 *
 * @param position
 *          the position
 * @return  the tab info
 */
private TabInfo getPrevious(final int position) {
    TabInfo currentTabInfo = history.get(position).pop();
    if (!history.get(position).isEmpty()) {
        currentTabInfo = history.get(position).peek();
    }
    return currentTabInfo;
}

/** The tab info class */
private static class TabInfo {

    /** The fragment class. */
    public Class fragmentClass;

    /** The args.*/
    public Bundle args;

    /**
     * Creates a new instance.
     *
     * @param fragmentClass
     *          the fragment class
     * @param args
     *          the args
     */
    public TabInfo(Class fragmentClass, Bundle args) {
        this.fragmentClass = fragmentClass;
        this.args = args;
    }

    @Override
    public boolean equals(final Object o) {
        return this.fragmentClass.getName().equals(o.getClass().getName());
    }

    @Override
    public int hashCode() {
        return fragmentClass.getName() != null ? fragmentClass.getName().hashCode() : 0;
    }

    @Override
    public String toString() {
        return "TabInfo{" +
                "fragmentClass=" + fragmentClass +
                '}';
    }
}

第一次添加所有选项卡时,我们需要调用createHistory()方法来创建初始历史记录

public void createHistory() {
    int position = 0;
    TOTAL_TABS = mTabs.size();
    for (TabInfo mTab : mTabs) {
        if (history.get(position) == null) {
            history.put(position, new Stack<TabInfo>());
        }
        history.get(position).push(new TabInfo(mTab.fragmentClass, mTab.args));
        position++;
    }
}

每次你想要替换一个片段到一个特定的标签,你调用: replace(final int position, final Class fragmentClass, final Bundle args)

/* Save the fragment to the history. */
    mActivity.getSupportFragmentManager().beginTransaction().addToBackStack(null).commit();

    /* Update the tabs. */
    updateTabs(new TabInfo(fragmentClass, args), position);

    /* Updates the history. */
    history.get(position).push(new TabInfo(mTabs.get(position).fragmentClass, mTabs.get(position).args));

    notifyDataSetChanged();

在back被按下时,你需要调用back()方法:

public void back() {
    int position = mActionBar.getSelectedTab().getPosition();
    if (!historyIsEmpty(position)) {
        /* In case there is not any other item in the history, then finalize the activity. */
        if (isLastItemInHistory(position)) {
            mActivity.finish();
        }
        final TabInfo currentTabInfo = getPrevious(position);
        mTabs.clear();
        for (int i = 0; i < TOTAL_TABS; i++) {
            if (i == position) {
                mTabs.add(new TabInfo(currentTabInfo.fragmentClass, currentTabInfo.args));
            } else {
                TabInfo otherTabInfo = history.get(i).peek();
                mTabs.add(new TabInfo(otherTabInfo.fragmentClass, otherTabInfo.args));
            }
        }
    }
    mActionBar.selectTab(mActionBar.getTabAt(position));
    notifyDataSetChanged();
}

解决方案与夏洛克动作栏和滑动手势。