Question

我使用FragmentStatePagerAdapter将视图分页器用于加载片段。当我第一次来它会工作，但如果我从寻呼机适配器重定向到其他片段并返回它将显示空白屏幕。

    **fragment_community.xml**

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

    <include
        android:id="@+id/includeTop"
        layout="@layout/layout_header"
        android:layout_width="match_parent"
        android:layout_height="50dp"
        />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_below="@+id/includeTop"
        android:orientation="vertical"
        >

        <android.support.design.widget.TabLayout
            android:id="@+id/tabAddFriend"
            android:layout_width="match_parent"
            android:layout_height="48dp"
            android:layout_alignParentTop="true"
            android:background="@drawable/tab_friend_selector"
            android:fadeScrollbars="false"
            app:tabGravity="fill"
            app:tabIndicatorHeight="4dp"
            app:tabMaxWidth="0dp"
            app:tabMode="fixed"
            app:tabSelectedTextColor="@color/colorDarkGray"
            app:tabTextColor="@color/colorGray">
        </android.support.design.widget.TabLayout>

        <android.support.v4.view.ViewPager
            android:id="@+id/pagerCommunity"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_below="@id/tabAddFriend"/>

    </LinearLayout>

</LinearLayout>

    **Community Fragment :**
    import android.os.Bundle;
    import android.support.design.widget.TabLayout;
    import android.support.v4.app.Fragment;
    import android.support.v4.app.FragmentActivity;
    import android.support.v4.app.FragmentManager;
    import android.support.v4.content.ContextCompat;
    import android.support.v4.view.ViewPager;
    import android.view.LayoutInflater;
    import android.view.View;
    import android.view.ViewGroup;
    import android.widget.ImageView;
    import android.widget.LinearLayout;    
    import com.****.app.R;
    import com.****.app.adapter.CommunityPagerAdapter;
    import com.****.app.customcontrol.CustomTextViewMedium;
    import com.****.app.customcontrol.CustomTextViewRegular;
    import com.****.app.utils.General;
    import com.****.app.utils.ManageFragment;

    public class CommunityFragment extends Fragment{

        public static final int FOLLOWERS = 0;
        public static final int FOLLOWING = 1;
        public static final int GROUPS = 2;
        public static String LOGTAG = CommunityFragment.class.getSimpleName ();
        // define activity layouts
        LinearLayout linearBack, linearAction;
        ImageView imgBack, imgAction;
        CustomTextViewRegular txtTitle;
        FragmentActivity activity;

        String[] tabList;
        //CustomViewPager pagerCommunity;
        ViewPager pagerCommunity;
        TabLayout tabAddFriend;

        FragmentManager manager;
        CommunityPagerAdapter communityPagerAdapter;
        String operation="";
        public CommunityFragment (){

        }

        @Override
        public void onCreate (Bundle savedInstanceState){
            super.onCreate (savedInstanceState);
            activity = this.getActivity ();
            tabList = activity.getResources ().getStringArray (R.array.communityArray);
             //Bundle bundle=activity.getIntent ().getExtr
            if(getArguments ()!=null){
                operation= getArguments ().getString (General.REQUEST_TYPE);
            }
        }

        @Override
        public View onCreateView (LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){
            View view = inflater.inflate (R.layout.fragment_community, container, false);

            linearAction = (LinearLayout) view.findViewById (R.id.linearAction);
            linearAction.setVisibility (View.VISIBLE);
            linearBack = (LinearLayout) view.findViewById (R.id.linearBack);
            imgBack = (ImageView) view.findViewById (R.id.imgBack);
            imgAction = (ImageView) view.findViewById (R.id.imgAction);
            imgAction.setImageResource (R.drawable.ic_block);

            txtTitle = (CustomTextViewRegular) view.findViewById (R.id.txtTitle);
            txtTitle.setText (getString (R.string.community));

            tabAddFriend = (TabLayout) view.findViewById (R.id.tabAddFriend);

            pagerCommunity = (ViewPager) view.findViewById (R.id.pagerCommunity);


            linearBack.setOnClickListener (new View.OnClickListener (){
                @Override
                public void onClick (View v){
                    ManageFragment.back (activity);
                }
            });

            imgBack.setOnClickListener (new View.OnClickListener (){
                @Override
                public void onClick (View v){
                    ManageFragment.back (activity);
                }
            });

            pagerCommunity.addOnPageChangeListener (new ViewPager.OnPageChangeListener (){
                @Override
                public void onPageScrolled (int position, float positionOffset, int positionOffsetPixels){

                }

                @Override
                public void onPageSelected (int position){

                    if (position == FOLLOWERS){
                        imgAction.setImageResource (R.drawable.ic_block);
                    } else if (position == FOLLOWING){
                        imgAction.setImageResource (R.drawable.ic_plus);
                    } else if (position == GROUPS){
                        imgAction.setImageResource (R.drawable.ic_plus);
                    }
                    updateCustomTabTextView (position);
                }

                @Override
                public void onPageScrollStateChanged (int state){

                }
            });
            linearAction.setOnClickListener (new View.OnClickListener (){
                @Override
                public void onClick (View v){

                    int position = pagerCommunity.getCurrentItem ();
                    if (position == FOLLOWERS){
                        imgAction.setImageResource (R.drawable.ic_block);
                        ManageFragment.replace (activity, R.id.content_frame, new BlockedUsersFragment (), BlockedUsersFragment.LOGTAG, BlockedUsersFragment.LOGTAG);

                    } else if (position == FOLLOWING){
                        imgAction.setImageResource (R.drawable.ic_plus);
                        ManageFragment.replace (activity, R.id.content_frame, new FollowingAddFragment (), FollowingAddFragment.LOGTAG, FollowingAddFragment.LOGTAG);
                    } else if (position == GROUPS){
                        imgAction.setImageResource (R.drawable.ic_plus);
                        ManageFragment.replace (activity, R.id.content_frame, new NewGroupFragment (), NewGroupFragment.LOGTAG, NewGroupFragment.LOGTAG);
                    }

                }
            });
            setTabLayout ();
            return view;
        }

        private void setTabLayout (){
            manager = activity.getSupportFragmentManager ();
            communityPagerAdapter = new CommunityPagerAdapter (activity, manager);
            pagerCommunity.setAdapter (communityPagerAdapter);
            tabAddFriend.setupWithViewPager (pagerCommunity);
            setCustomTabTextView ();

            if(!operation.equalsIgnoreCase ("")){
                int type=Integer.parseInt (operation);
                if(type==FOLLOWERS){
                    imgAction.setImageResource (R.drawable.ic_block);
                }else if(type==FOLLOWING){
                    imgAction.setImageResource (R.drawable.ic_plus);
                }
                pagerCommunity.setCurrentItem (type);
            }
        }

        public void updateCustomTabTextView (int position){
            for (int i = 0; i < tabAddFriend.getTabCount (); i++){
                View view = tabAddFriend.getTabAt (i).getCustomView ();
                CustomTextViewMedium textTabTitle = (CustomTextViewMedium) view.findViewById (R.id.textTabTitle);
                if (i == position){
                    textTabTitle.setTextColor (ContextCompat.getColor (activity, R.color.colorDarkGray));
                } else{
                    textTabTitle.setTextColor (ContextCompat.getColor (activity, R.color.colorGray));
                }
            }
        }

        private void setCustomTabTextView (){
            for (int i = 0; i < tabAddFriend.getTabCount (); i++){
                TabLayout.Tab tab = tabAddFriend.getTabAt (i);
                View view = LayoutInflater.from (activity).inflate (R.layout.layout_add_friend_tab, null);
                CustomTextViewMedium textTabTitle = (CustomTextViewMedium) view.findViewById (R.id.textTabTitle);
                textTabTitle.setText (tabList[i]);
                textTabTitle.setTextSize (12);
                if (pagerCommunity.getCurrentItem () == i){
                    textTabTitle.setTextColor (ContextCompat.getColor (activity, R.color.colorDarkGray));
                } else{
                    textTabTitle.setTextColor (ContextCompat.getColor (activity, R.color.colorGray));
                }
                tab.setCustomView (view);
            }
        }
    }

    **CommunityPagerAdapter.java**

    import android.app.Activity;
    import android.support.v4.app.Fragment;
    import android.support.v4.app.FragmentManager;
    import android.support.v4.app.FragmentStatePagerAdapter;

    import com.****.app.R;
    import com.****.app.fragment.ActivityFragment;
    import com.****.app.fragment.FollowingFragment;
    import com.****.app.fragment.GroupFragment;

    public class CommunityPagerAdapter extends FragmentStatePagerAdapter{

        Activity activity;

        public CommunityPagerAdapter (Activity activity, FragmentManager fm){
            super (fm);
            this.activity = activity;
        }

        @Override
        public Fragment getItem (int position){
            switch (position){
                case 0:
                    return new ActivityFragment ();
                case 1:
                    return new FollowingFragment ();
                case 2:
                    return new GroupFragment ();
            }
            return null;
        }

        @Override
        public int getCount (){
            return 3;
        }

        @Override
        public CharSequence getPageTitle (int position){
            String title = " ";
            switch (position){
                case 0:
                    title = activity.getResources ().getString (R.string.followers);
                    break;
                case 1:
                    title = activity.getResources ().getString (R.string.following);
                    break;
                case 2:
                    title = activity.getResources ().getString (R.string.groups);
                    break;
            }
            return title;
        }

    }

Answer 1

为从其他帖子中提供解决方案而投票否决？谢谢！

好的，我再次尝试描述发生了什么以及为什么Fragment没有重新连接：

已恢复的Fragment（从又一次弹出后堆栈开始）是完全按照View层次结构而不是弹出状态的View层次结构重新创建的。一种解决方法是，确保已还原的Fragment的{{1}}被重新附加，其中之一是编写View的另一种实现方式，以确保使用了原始代码，并且进行了以下更改：

FragmentStatePagerAdapter

稍作修改为：

@NonNull
@Override
public Object instantiateItem(@NonNull ViewGroup container, int position) {
    // If we already have this item instantiated, there is nothing
    // to do.  This can happen when we are restoring the entire pager
    // from its saved state, where the fragment manager has already
    // taken care of restoring the fragments we previously had instantiated.
    if (mFragments.size() > position) {
        Fragment f = mFragments.get(position);
        if (f != null) {
            return f;
        }
    }
...
}

请查看我最近的帖子，了解一个非常相似的情况以及解决方法。

https://stackoverflow.com/a/52661538/6391598

Answer 2

我遇到了viewpager的这个问题，最后通过删除片段并再次加载相同的片段来解决以下是代码

FragmentManager fm = getSupportFragmentManager();
Fragment f = fm.findFragmentById(R.id.fragments);
FragmentManager fragmentManager = getSupportFragmentManager();
android.support.v4.app.FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();

fragmentTransaction.remove(fragment); // here fragment is 
fragmentTransaction.commit();

Answer 3

在面对问题的3天后，对我有用的是 onCreateView 方法，检查列表大小是否大于零，然后再次设置其适配器

if (list.size() > 0) {
    viewpager.setAdapter(viewPagerAdapter);
}

当我们回来时，视图寻呼机片段状态寻呼机适配器中的白色屏幕？

3 个答案: