当我们回来时，视图寻呼机片段状态寻呼机适配器中的白屏? [英] White screen in view pager fragment state pager adapter when we come back?
本文介绍了当我们回来时，视图寻呼机片段状态寻呼机适配器中的白屏?的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我已经使用FragmentStatePagerAdapter将视图分页器用于加载片段. 当我第一次来时它将正常工作，但是如果我从寻呼机适配器重定向到其他片段并回来，它将显示空白屏幕.
I have used view pager for load fragments using FragmentStatePagerAdapter. when i will come first time it will working but if i am redirect to other fragment from pager adapter and come back it will display blank screen.
**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;
}
}
推荐答案
为从其他帖子中提供解决方案而投票否决?谢谢！
Down-voted for providing the solution from another post? Thanks!
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:
Alright, I give this another try to describe what happens and why Fragments aren't re-attached:
还原后的Fragment(从又回到弹出堆栈)是完全由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 s'View被重新附加，并且其中之一是在使用原始代码并进行以下更改的情况下编写FragmentStatePagerAdapter的另一种实现:
The restored Fragment (from going back a.k.a. popping the back-stack) is fully re-created with a View-hierarchy but not the View-hierarchy of the popped state. A workaround for this is to make sure that already restored Fragments' View is re-attached and one of doing it is to write another implementation of FragmentStatePagerAdapter were the original code is used and the following changes are made:
@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;
}
}
...
}
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) {
if (mCurTransaction == null) {
mCurTransaction = mFragmentManager.beginTransaction();
}
mCurTransaction.detach(f);
mCurTransaction.attach(f);
return f;
}
}
...
}
请查看我最近的帖子，了解一个非常相似的场景以及我的解决方法.
Please have a look at my recent post for a very similar scenario and the way I solved it.
https://stackoverflow.com/a/52661538/6391598
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