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POViewPager inside Tab doesn't display items properly
 

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  1. POViewPager inside Tab doesn't display items properly
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    <p>I have a FragmentActivity that sets up a tabhost. Each tab is a simple Fragment called TabFragment. TabFragment has a ViewPager, in this case it is an InfiniteViewPager by <a href="https://stackoverflow.com/questions/7546224/viewpager-as-a-circular-queue-wrapping/9656874">antonyt</a> (discussed here: <a href="https://stackoverflow.com/questions/7546224/viewpager-as-a-circular-queue-wrapping/9656874">ViewPager as a circular queue / wrapping</a>).</p> <p>The (main) problems are the following:</p> <ol> <li><p>I start up the application. I click on the second tab. There is only a blank screen when I should see identical things as in the first tab. After scrolling right a few times I do see my TextViews.</p></li> <li><p>Scrolling fragments in ViewPagers and changing tabs eventually leads to a halt and FC with no clear Exception being thrown.</p></li> </ol> <p>This is my first take on Fragments and, I must confess, I do not understand the observed behaviour.</p> <p>Any hints would be greatly appreciated.</p> <p>The whole project is <a href="http://www.sendspace.com/file/rtguqq" rel="nofollow noreferrer">here</a>.</p> <p>The code:</p> <p>FragmentActivity with TabHost:</p> <pre><code> package com.example.viewpagerintab; import java.util.HashMap; import android.content.Context; import android.os.Bundle; import android.support.v4.app.Fragment; import android.support.v4.app.FragmentActivity; import android.support.v4.app.FragmentTransaction; import android.view.View; import android.widget.TabHost; import android.widget.TabHost.TabContentFactory; public class TabsFragmentActivity extends FragmentActivity implements TabHost.OnTabChangeListener { private TabHost mTabHost; private HashMap mapTabInfo = new HashMap(); private TabInfo mLastTab = null; public TabsFragmentActivity() { } private class TabInfo { private String tag; private Class clss; private Bundle args; private Fragment fragment; TabInfo(String tag, Class classObject, Bundle args) { this.tag = tag; this.clss = classObject; this.args = args; } } class TabFactory implements TabContentFactory { private final Context mContext; /** * @param context */ public TabFactory(Context context) { mContext = context; } /** * (non-Javadoc) * * @see android.widget.TabHost.TabContentFactory#createTabContent(java.lang.String) */ public View createTabContent(String tag) { View v = new View(mContext); v.setMinimumWidth(0); v.setMinimumHeight(0); return v; } } /** * (non-Javadoc) * * @see android.support.v4.app.FragmentActivity#onCreate(android.os.Bundle) */ protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.tabs); initialiseTabHost(savedInstanceState); if (savedInstanceState != null) { mTabHost.setCurrentTabByTag(savedInstanceState.getString("tab")); } } /** * (non-Javadoc) * * @see android.support.v4.app.FragmentActivity#onSaveInstanceState(android.os.Bundle) */ protected void onSaveInstanceState(Bundle outState) { outState.putString("tab", mTabHost.getCurrentTabTag()); super.onSaveInstanceState(outState); } private void initialiseTabHost(Bundle args) { mTabHost = (TabHost) findViewById(android.R.id.tabhost); mTabHost.setup(); TabInfo tabInfo = null; tabInfo = new TabInfo("Discover", TabFragmentD.class, args); TabsFragmentActivity.addTab(this, mTabHost, mTabHost.newTabSpec("Discover").setIndicator("Discover"), tabInfo); mapTabInfo.put(tabInfo.tag, tabInfo); tabInfo = new TabInfo("Friends", TabFragmentF.class, args); TabsFragmentActivity .addTab(this, mTabHost, mTabHost.newTabSpec("Friends") .setIndicator("Friends"), tabInfo); mapTabInfo.put(tabInfo.tag, tabInfo); onTabChanged("Discover"); mTabHost.setOnTabChangedListener(this); } /** * @param activity * @param tabHost * @param tabSpec * @param clss * @param args */ private static void addTab(TabsFragmentActivity activity, TabHost tabHost, TabHost.TabSpec tabSpec, TabInfo tabInfo) { // Attach a Tab view factory to the spec tabSpec.setContent(activity.new TabFactory(activity)); String tag = tabSpec.getTag(); // Check to see if we already have a fragment for this tab, probably // from a previously saved state. If so, deactivate it, because our // initial state is that a tab isn't shown. tabInfo.fragment = activity.getSupportFragmentManager() .findFragmentByTag(tag); if (tabInfo.fragment != null && !tabInfo.fragment.isDetached()) { FragmentTransaction ft = activity.getSupportFragmentManager() .beginTransaction(); ft.detach(tabInfo.fragment); ft.commit(); activity.getSupportFragmentManager().executePendingTransactions(); } tabHost.addTab(tabSpec); } /** * (non-Javadoc) * * @see android.widget.TabHost.OnTabChangeListener#onTabChanged(java.lang.String) */ public void onTabChanged(String tag) { TabInfo newTab = mapTabInfo.get(tag); if (mLastTab != newTab) { FragmentTransaction ft = getSupportFragmentManager() .beginTransaction(); if (mLastTab != null) { if (mLastTab.fragment != null) { ft.detach(mLastTab.fragment); } } if (newTab != null) { if (newTab.fragment == null) { newTab.fragment = Fragment.instantiate(this, newTab.clss.getName(), newTab.args); ft.add(R.id.realtabcontent, newTab.fragment, newTab.tag); } else { ft.attach(newTab.fragment); } } mLastTab = newTab; ft.commit(); getSupportFragmentManager().executePendingTransactions(); } } } </code></pre> <p>TabFragment containing InfiniteViewPager:</p> <pre><code> package com.example.viewpagerintab; import java.util.List; import java.util.Vector; import android.os.AsyncTask; import android.os.Bundle; import android.support.v4.app.Fragment; import android.support.v4.app.FragmentPagerAdapter; import android.support.v4.view.ViewPager; import android.support.v4.view.ViewPager.OnPageChangeListener; import android.util.Log; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.LinearLayout; import com.antonyt.infiniteviewpager.InfinitePagerAdapter; import com.example.viewpagerintab.pager.SimpleAdapter; public class TabFragment extends Fragment { private static final String TAG = TabFragment.class.getSimpleName(); protected View mView; ViewPager mViewPager; private InfinitePagerAdapter mPagerAdapter; PageListener pageListener; public TabFragment() { } /** * (non-Javadoc) * * @see android.support.v4.app.Fragment#onCreateView(android.view.LayoutInflater, * android.view.ViewGroup, android.os.Bundle) */ public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { Log.d(TAG, "onCreateView - called"); if (container == null) { // We have different layouts, and in one of them this // fragment's containing frame doesn't exist. The fragment // may still be created from its saved state, but there is // no reason to try to create its view hierarchy because it // won't be displayed. Note this is not needed -- we could // just run the code below, where we would create and return // the view hierarchy; it would just never be used. return null; } pageListener = new PageListener(); mView = (LinearLayout) inflater.inflate(R.layout.tab, container, false); List fragments = new Vector(); fragments.add(DayFragment.newInstance("one")); fragments.add(DayFragment.newInstance("two")); fragments.add(DayFragment.newInstance("three")); fragments.add(DayFragment.newInstance("four")); mPagerAdapter = new InfinitePagerAdapter( new com.example.viewpagerintab.PagerAdapter( getFragmentManager(), fragments)); mViewPager = (ViewPager) mView.findViewById(R.id.viewpager); mViewPager.setOnPageChangeListener(pageListener); new setAdapterTask().execute(); Log.d(TAG, "onCreateView - finished"); return mView; } private class setAdapterTask extends AsyncTask { protected Void doInBackground(Void... params) { return null; } @Override protected void onPostExecute(Void result) { mViewPager.setAdapter(mPagerAdapter); } } class PageListener implements OnPageChangeListener { private final String TAG = PageListener.class.getSimpleName(); @Override public void onPageScrollStateChanged(int arg0) { Log.d(TAG, "onPageScrollStateChanged(..) to: " + arg0); } @Override public void onPageScrolled(int arg0, float arg1, int arg2) { // Log.d(TAG, "onPageScrolled(..) - called"); } @Override public void onPageSelected(int arg0) { Log.d(TAG, "onPageSelected(..) selected: " + arg0); } } } </code></pre> <p>TabFragmentD and TabFragmentF are near identical:</p> <pre><code> public class TabFragmentD extends TabFragment { public TabFragmentD() { } } </code></pre> <p>DayFragment containing just one TextView:</p> <pre><code> package com.example.viewpagerintab; import android.os.Bundle; import android.support.v4.app.Fragment; import android.util.Log; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.LinearLayout; import android.widget.TextView; public class DayFragment extends Fragment { private static final String TAG = DayFragment.class.getSimpleName(); protected View mView; protected TextView tvDay; public DayFragment() { } /** * (non-Javadoc) * * @see android.support.v4.app.Fragment#onCreateView(android.view.LayoutInflater, * android.view.ViewGroup, android.os.Bundle) */ public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { if (container == null) { // We have different layouts, and in one of them this // fragment's containing frame doesn't exist. The fragment // may still be created from its saved state, but there is // no reason to try to create its view hierarchy because it // won't be displayed. Note this is not needed -- we could // just run the code below, where we would create and return // the view hierarchy; it would just never be used. return null; } mView = (LinearLayout) inflater.inflate(R.layout.day, container, false); tvDay = (TextView) mView.findViewById(R.id.tvText); String text = getArguments().getString("text"); Log.d(TAG, "creating view with text: " + text); tvDay.setText(text); return mView; } public static DayFragment newInstance(String text) { Log.d(TAG, "newInstance with text: " + text); DayFragment f = new DayFragment(); // Supply text input as an argument. Bundle args = new Bundle(); args.putString("text", text); f.setArguments(args); return f; } } </code></pre> <p>PagerAdapter:</p> <pre><code> package com.example.viewpagerintab; import java.util.List; import android.support.v4.app.Fragment; import android.support.v4.app.FragmentManager; import android.support.v4.app.FragmentPagerAdapter; public class PagerAdapter extends FragmentPagerAdapter { private List fragments; public PagerAdapter(FragmentManager fm, List fragments) { super(fm); this.fragments = fragments; } /* * (non-Javadoc) * * @see android.support.v4.app.FragmentPagerAdapter#getItem(int) */ @Override public Fragment getItem(int position) { return fragments.get(position); } /* * (non-Javadoc) * * @see android.support.v4.view.PagerAdapter#getCount() */ @Override public int getCount() { return this.fragments.size(); } } </code></pre> <p>InfiniteViewPager and InfinitePageAdapter are on <a href="https://github.com/antonyt/InfiniteViewPager" rel="nofollow noreferrer">antonyt's github</a>.</p> <p>tabs.xml:</p> <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt; &lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" &gt; &lt;TabHost android:id="@android:id/tabhost" android:layout_width="fill_parent" android:layout_height="fill_parent" &gt; &lt;LinearLayout android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" &gt; &lt;TabWidget android:id="@android:id/tabs" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_weight="0" android:orientation="horizontal" /&gt; &lt;FrameLayout android:id="@android:id/tabcontent" android:layout_width="0dp" android:layout_height="0dp" android:layout_weight="0" /&gt; &lt;FrameLayout android:id="@+android:id/realtabcontent" android:layout_width="fill_parent" android:layout_height="0dp" android:layout_weight="1" /&gt; &lt;/LinearLayout&gt; &lt;/TabHost&gt; &lt;/LinearLayout&gt; </code></pre> <p>tab.xml:</p> <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt; &lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:background="@android:color/black" &gt; &lt;com.antonyt.infiniteviewpager.InfiniteViewPager android:id="@+android:id/viewpager" android:layout_width="fill_parent" android:layout_height="fill_parent" /&gt; &lt;/LinearLayout&gt; </code></pre> <p>day.xml:</p> <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt; &lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:background="@android:color/black" android:gravity="center" &gt; &lt;TextView android:id="@+id/tvText" android:layout_width="wrap_content" android:layout_height="wrap_content" android:textColor="@android:color/white" /&gt; &lt;/LinearLayout&gt; </code></pre> <p><strong>UPDATE</strong></p> <p>As pointed out by CommonsWare, Android has problems with Fragments within Fragments.</p> <p>I modified tabs.xml to:</p> <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt; &lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" &gt; &lt;TabHost android:id="@android:id/tabhost" android:layout_width="fill_parent" android:layout_height="fill_parent" &gt; &lt;LinearLayout android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" &gt; &lt;TabWidget android:id="@android:id/tabs" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_weight="0" android:orientation="horizontal" /&gt; &lt;FrameLayout android:id="@android:id/tabcontent" android:layout_width="0dp" android:layout_height="0dp" android:layout_weight="0" /&gt; &lt;FrameLayout android:id="@+android:id/realtabcontent" android:layout_width="fill_parent" android:layout_height="0dp" android:layout_weight="0" /&gt; &lt;com.antonyt.infiniteviewpager.InfiniteViewPager android:id="@+android:id/viewpager" android:layout_width="fill_parent" android:layout_height="0dp" android:layout_weight="1" /&gt; &lt;/LinearLayout&gt; &lt;/TabHost&gt; &lt;/LinearLayout&gt; </code></pre> <p>and created empty TabFragments (tab.xml):</p> <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt; &lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="0dp" android:layout_height="0dp" &gt; &lt;/LinearLayout&gt; </code></pre> <p>So now switching tabs is nearly independent of swiping.</p> <p>Only drawback is that there was a very annoying problem with any attempts to set current position of the ViewPager to 0 after changing tabs (app just crashed with no exception).</p>
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