更改片段后，ViewPager的内容消失 [英] Content of ViewPager disapear after changing fragments
本文介绍了更改片段后，ViewPager的内容消失的处理方法，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
我带着一个新问题回到这里.因此，目前我创建了一个应用程序，当您单击按钮时，它可以从一个片段切换到另一个片段.在这2个片段中，有2个viewPagers，它们创建了自定义数量的按钮.但是问题是，当我从一个片段切换到另一个片段，然后又切换回来时，第一个片段的内容不再在这里.我尝试了很多事情，没有任何真正的帮助.我希望你能帮助我.预先感谢.
i'm back here with a new Question. So at the moment i created an app , that can switch from a fragment to another fragment when you click on a button. And inside those 2 fragments there is 2 viewPagers, whose create a custom number of buttons. But the problem is that when i switch from a fragment to the other one, and then i switch back , the content of the first one is no longer here. I tried a lot of things and nothing really help me. And i hope you can help me. Thanks in advance.
主要活动:
public class MainActivity extends AppCompatActivity {
String identifiant=null;
BottomBar bottombar;
ProgressBar progressBar;
ImageButton imageButton;
TextView nomson;
RelativeLayout aaaa;
FragmentWhizz fragmentWhizz;
FragmentPlaylist fragmentPlaylist;
FragmentManager fm;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
autorisation();
fragmentWhizz = new FragmentWhizz();
fragmentPlaylist=new FragmentPlaylist();
Fragment fragment = new FragmentConnexion();
FragmentManager fm = getFragmentManager();
FragmentTransaction transaction = fm.beginTransaction();
transaction.replace(R.id.contentFragment, fragment);
transaction.commit();
bottombar = (BottomBar) findViewById(bottomBar);
aaaa = (RelativeLayout) findViewById(R.id.aaaa);
bottombar.setVisibility(View.INVISIBLE);
bottombar.setOnTabSelectListener(new OnTabSelectListener() {
@Override
public void onTabSelected(@IdRes int tabId) {
if (tabId == R.id.tab_whiz) {
if(identifiant !=null){
changementFragment(fragmentWhizz);
}
}
if (tabId == R.id.tab_playlist) {
if(identifiant !=null){
changementFragment(fragmentPlaylist);
}
}
if (tabId == R.id.tab_reveil) {
if(identifiant !=null){
changementFragment(new FragmentReveil());
}
}
if (tabId == R.id.tab_param) {
if(identifiant !=null){
changementFragment(new FragmentParam());
}
}
}
});
}
public void changementFragment(final Fragment fragment){
runOnUiThread(new Runnable() {
public void run() {
fm = getFragmentManager();
FragmentTransaction ft =fm.beginTransaction();
ft.setCustomAnimations(android.R.animator.fade_in,android.R.animator.fade_out);
ft.replace(R.id.contentFragment, fragment).commit();
}
});
}
}
具有ViewPager的2个片段之一:
One of the 2 fragments that have the ViewPager:
public class FragmentPlaylist extends Fragment {
SlideToutesPlaylist fragmentAllPlaylist = new SlideToutesPlaylist();
SlideUserPlaylist fragmentUserPlaylist = new SlideUserPlaylist();
ViewPager mViewPager;
FloatingActionButton floatbutton;
private FragmentActivity myContext;
@Override
public void onAttach(Activity activity) {
myContext=(FragmentActivity) activity;
super.onAttach(activity);
}
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setRetainInstance(true);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View myView = inflater.inflate(R.layout.playlist, container, false);
DeplacerBoutton deplacer = new DeplacerBoutton(getActivity(),2);
floatbutton = (FloatingActionButton) myView.findViewById(R.id.floatingActionButton);
floatbutton.setOnTouchListener(deplacer);
mViewPager = (ViewPager) myView.findViewById(R.id.slide);
mViewPager.setAdapter(new SamplePagerAdapter(myContext.getSupportFragmentManager()));
Log.i("test","test");
return myView;
}
public class SamplePagerAdapter extends FragmentStatePagerAdapter {
SamplePagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public android.support.v4.app.Fragment getItem(int position) {
/** Show a Fragment based on the position of the current screen */
if (position == 0) {
return fragmentAllPlaylist;
} else
return fragmentUserPlaylist;
}
@Override
public int getCount() {
// Show 2 total pages.
return 2;
}
}
}
最后一个片段显示在viewPager上:
And finally one fragment displayed on the viewPager:
public class SlideToutesPlaylist extends Fragment {
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setRetainInstance(true);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View myView = inflater.inflate(R.layout.playlistall, container, false);
AffichePlaylist(myView);
return myView;
}
public void AffichePlaylist(View myView){
ExecHttpGetRequest requete = new ExecHttpGetRequest();
requete.execute("an IP");
LinearLayout aaa = (LinearLayout) myView.findViewById(R.id.aaa);
try {
if (requete.get() != null) {
JSONObject jsonObj = new JSONObject(requete.get());
JSONArray jSon = jsonObj.getJSONArray("valeurs");
for (int i = 0; i < jSon.length(); i++) {
JSONObject c = jSon.getJSONObject(i);
final String nom_playlist = c.getString("nom_playlist");
final String id_playlist = c.getString("id_playlist");
final String id_createur = c.getString("id_createur");
final String nb_vote = c.getString("nb_vote");
Button bouton = new Button(getContext());
bouton.setText(nom_playlist);
aaa.addView(bouton);
}
}
} catch (InterruptedException | ExecutionException | JSONException e) {
e.printStackTrace();
}
}
}
编辑好吧，我终于用您的解决方案解决了我的问题，但是现在我遇到了这个问题:
EDIT Ok finally i solved my problem with your solution but now i have this problem :
java.lang.NullPointerException: Attempt to invoke virtual method 'int java.util.ArrayList.size()' on a null object reference
at android.support.v4.app.FragmentManagerImpl.getFragment(FragmentManager.java:873)
at android.support.v4.app.FragmentStatePagerAdapter.restoreState(FragmentStatePagerAdapter.java:215)
at android.support.v4.view.ViewPager.onRestoreInstanceState(ViewPager.java:1481)
at android.view.View.dispatchRestoreInstanceState(View.java:14762)
at android.view.ViewGroup.dispatchRestoreInstanceState(ViewGroup.java:3123)
at android.view.ViewGroup.dispatchRestoreInstanceState(ViewGroup.java:3129)
at android.view.View.restoreHierarchyState(View.java:14740)
at android.support.v4.app.Fragment.restoreViewState(Fragment.java:475)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1329)
at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1528)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1595)
at android.support.v4.app.BackStackRecord.executeOps(BackStackRecord.java:757)
at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2355)
at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2146)
at android.support.v4.app.FragmentManagerImpl.optimizeAndExecuteOps(FragmentManager.java:2098)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2008)
at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:710)
at android.os.Handler.handleCallback(Handler.java:746)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5443)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:728)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
推荐答案
要在另一个片段中填充片段，您需要使用getChildFragmentManager()而不是 myContext.getSupportFragmentManager().
To inflate fragments inside another fragment you need tu use getChildFragmentManager() instead of myContext.getSupportFragmentManager().
按以下方式使用FragmentStatePagerAdapter:
Use FragmentStatePagerAdapter as follows:
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentStatePagerAdapter;
import java.util.ArrayList;
import java.util.List;
public class ViewPagerAdapter extends FragmentStatePagerAdapter {
private List<Fragment> mFragmentList = new ArrayList<>();
private List<String> mFragmentTitleList = new ArrayList<>();
public ViewPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
return mFragmentList.get(position);
}
//Check if the list is empty before return the size
@Override
public int getCount() {
return mFragmentList != null ? mFragmentList.size() : 0;
}
public void addFragment(Fragment fragment, String title) {
mFragmentList.add(fragment);
mFragmentTitleList.add(title);
}
public void addFragment(Fragment fragment) {
mFragmentList.add(fragment);
}
@Override
public CharSequence getPageTitle(int position) {
if (!mFragmentTitleList.isEmpty()) {
return mFragmentTitleList.get(position);
}
return "";
}
}
然后在片段中添加要显示在viewPager中的片段:
Then in your fragment just add the fragments you want to show in the viewPager:
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.annotation.Nullable;
import android.support.design.widget.TabLayout;
import android.support.v4.content.ContextCompat;
import android.support.v4.view.ViewPager;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
...
viewPager = (ViewPager) view.findViewById(R.id.viewpager);
adapter = new ViewPagerAdapter(getChildFragmentManager());
adapter.addFragment(SlideToutesPlaylist.newInstance(), getString(R.string.title));
adapter.addFragment(SlideToutesPlaylist.newInstance(), getString(R.string.title));
viewPager.setAdapter(adapter);
viewPager.setOffscreenPageLimit(2);
这篇关于更改片段后，ViewPager的内容消失的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
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