如何在 FragmentPagerAdapter 中添加片段标签以便稍后引用片段？

Posted 2023-04-13

【中文标题】如何在 FragmentPagerAdapter 中添加片段标签以便稍后引用片段？

【英文标题】：How to add fragment Tag in a FragmentPagerAdapter to reference the fragment later?

【发布时间】：2017-10-23 07:08:44

【问题描述】：

我尝试了以下方法，但没有帮助。如何从 FragmentPagerAdapter 设置片段的标签或访问标签？

        @Override
public Fragment getItem(int position) 

    MainActivity activity = (MainActivity)mcontext;

    if (position == 0) 
       Fragment discoverFragment =  new DiscoverFragment();
        activity.getSupportFragmentManager().beginTransaction().add(discoverFragment, "discover").commit();
        return discoverFragment;
     else if (position == 1)
        Fragment myFeedFragment =  new MyFeedFragment();
        activity.getSupportFragmentManager().beginTransaction().add(myFeedFragment, "myfeed").commit();
        return myFeedFragment;
     else 
        Fragment filterFragment =  new FilterFragment();
        activity.getSupportFragmentManager().beginTransaction().add(filterFragment, "filter").commit();
        return filterFragment;
    

【问题讨论】：

findFragmentByTag 函数可以使用This will be helpful

【参考方案1】：

您似乎正确设置了标签。无论如何，这种方式应该可行。

设置标签：

MyFeedFragment myFeedFragment= new MyFeedFragment();
getSupportFragmentManager().beginTransaction().add(R.id.fragmentContainer, myFeedFragment, "myfeed");
fragmentTransaction.commit();

然后你可以通过搜索标签得到它：

    List fragments = getSupportFragmentManager().getFragments();

    Fragment discoverFrag = null;
    Fragment myFeedFragment = null;
    Fragment filterFragment = null;

    for (int i = 0; i < fragments.size(); i++) 
        if (((Fragment) fragments.get(i)).getTag() == "discover")
            discoverFrag = (Fragment) fragments.get(i);

        if (((Fragment) fragments.get(i)).getTag() == "myfeed")
            myFeedFragment = (Fragment) fragments.get(i);

        if (((Fragment) fragments.get(i)).getTag() == "filter")
            filterFragment = (Fragment) fragments.get(i);
    

【讨论】：

当我使用我的代码 java.lang.IllegalStateException: Can not perform this action after onSaveInstanceState

然后在上面试试这个。

试过你的方法。得到错误 java.lang.IllegalStateException: Can't change tag of fragment DiscoverFragment1488c4bd id=0x7f0d00a8 myfeed: is myfeed now android:switcher:2131558536:0

您需要更具体。发布您的完整堆栈跟踪和发生崩溃的代码行。此外，您想要参考的适配器和片段/活动的发布代码

【参考方案2】：

使用这个类作为你的适配器

class SwipeAdapter extends FragmentPagerAdapter 
        private Map<Integer, String> mFragmentTags;
        private FragmentManager mFragmentManager;

        private String mPagetile[];

        public SwipeAdapter(FragmentManager fm, Context context) 
            super(fm);
            mPagetile = context.getResources().getStringArray(R.array.pageTitle);
            mFragmentManager = fm;
            mFragmentTags = new HashMap<>();
        

        @Override
        public Fragment getItem(int position) 
            switch (position) 
                case 0:
                    return new "Your_fragment";
                default:
                    break;
            
            return null;
        

        @Override
        public Object instantiateItem(ViewGroup container, int position) 
            Object obj = super.instantiateItem(container, position);
            if (obj instanceof Fragment) 
                Fragment f = (Fragment) obj;
                String tag = f.getTag();
                mFragmentTags.put(position, tag);
            
            return obj;
        

        public Fragment getFragment(int position) 
            String tag = mFragmentTags.get(position);
            if (tag == null)
                return null;
            return mFragmentManager.findFragmentByTag(tag);
        

        @Override
        public CharSequence getPageTitle(int position) 
            return mPagetile[position];
        

        @Override
        public int getCount() 
            return "Number of fragments";
        
    

现在使用 SwipeAdapter 的实例调用 getFrament(int "position of fragment"); 希望你能明白。

【讨论】：

gettag() 方法给出 null。我们应该在 fragmentpagerAdapter 中设置 Tag 值？

【参考方案3】：

要检索 FragmentPagerAdapter 中使用的片段，您可以在任何地方执行此操作 (Kotlin)：

for (fragment in supportFragmentManager.fragments) 
    if (fragment is YourFragment) 
        val yourFragment = fragment as YourFragment