Develop Reference

Fragment in ViewPager using FragmentPagerAdapter is blank the first time activity is loaded

I'm creating an app with vertical page adapter using FragmentStatePagerAdapter. The big issue i'm facing is, data is not displayed on the textview on first app launch but is displayed on scrolling the page. I believe the fragment view is delaying to create textview because, on my LoadAlbumDataCompleted() function inside Fragmentone.class, i'm able to print the data returned or also output via toast but is not getting populated to the textview.
Kindly help.
MainActivity.class
public class MainActivity extends FragmentActivity implements LoadAalbumsTotalListener {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mAdapter = new MainActivityVSlideAdapter(this, getSupportFragmentManager(), NUMBER_OF_PAGES);
mPager.setAdapter(mAdapter);
LoadTotalAlbumsNum.BindAlbumsTotalListener(this);
}
#Override
public void OnLoadAlbumsCompleted(String total) {
if(total.trim().equalsIgnoreCase("")){
NUMBER_OF_PAGES=0;
}else{
NUMBER_OF_PAGES=Integer.parseInt(total.trim());
}
mAdapter = new MainActivityVSlideAdapter(this, getSupportFragmentManager(), NUMBER_OF_PAGES);
mPager.setAdapter(mAdapter);
}
}
MainActivityVSlideAdapter.class Adapter
public class MainActivityVSlideAdapter extends FragmentStatePagerAdapter {
static int NUMBER_OF_PAGES;
private Context con;
public MainActivityVSlideAdapter(Context con, FragmentManager fm, int NUMBER_OF_PAGES) {
super(fm);
this.con=con;
this.NUMBER_OF_PAGES=NUMBER_OF_PAGES;
}
#Override
public int getCount() {
return NUMBER_OF_PAGES;
}
#Override
public Fragment getItem(int position) {
return FragmentOne.newInstance(position);
}
}
Fragmentone.class
public class FragmentOne extends Fragment implements LoadAlbumDataListener {
private static final String MY_NUM_KEY = "num";
private int mNum;
private TextView SaloonName;
private TextView location;
// You can modify the parameters to pass in whatever you want
public static FragmentOne newInstance(int num) {
FragmentOne f = new FragmentOne();
Bundle args = new Bundle();
args.putInt(MY_NUM_KEY, num);
f.setArguments(args);
return f;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//get argument from
mNum = getArguments() != null ? getArguments().getInt(MY_NUM_KEY) : 0;
session=new Session(getActivity());
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment_one, container, false);
Methods methods=new Methods(getActivity());
// v.setBackgroundColor(mColor);
SaloonName = v.findViewById(R.id.SaloonName);
location=v.findViewById(R.id.location);
new LoadAlbumData(getActivity()).execute(getString(R.string.urlAddress)+"load-album-data.php", String.valueOf(mNum));
LoadAlbumData.BindLoadAlbumDataListener(this);
return v;
}
#Override
public void LoadAlbumDataCompleted(String s) {
JSONArray jsonPicsArray = null;
JSONObject jsonObj;
String BusinessLocation=null;
try {
jsonPicsArray = new JSONArray(s);
businessName = jsonObj.getString("businessName");
BusinessLocation = jsonObj.getString("location");;
}
Toast.makeText(getActivity(), businessName, Toast.LENGTH_LONG).show();
SaloonName.setText(businessName);
location.setText(BusinessLocation);
} catch (JSONException e) {
e.printStackTrace();
}
}
}

From your code, it looks like, you are not setting the LoadAlbumDataListener correctly. Instead of statically setting the listener. Pass reference in constructor of your LoadAlbumData Asynctask
remove this line
LoadAlbumData.BindLoadAlbumDataListener(this);
replace
new LoadAlbumData(getActivity()).execute(getString(R.string.urlAddress)+"load-album-data.php", String.valueOf(mNum));
with
new LoadAlbumData(getActivity(), this).execute(getString(R.string.urlAddress)+"load-album-data.php", String.valueOf(mNum));
Modify your asynctask to have reference of LoadAlbumDataListener
Also as a good practice, never store strong reference of activity or fragment in your asynctask. Use WeakReference.

False data in customList in a dynamically created fragment

I have an Activity with 2 fragments.
Declared a ParentTabFragment in my Activity in which there is a TabLayout and a ViewPager.
There's a method in my ParentTabFragment called addPage which gets called in the Activity.
The addPage has another method called addFrag which is called from a ViewPagerAdapter creating the views in the ChildTabFragment dynamically.
There is a for loop which runs in the Activity, so the Fragments are created according to the number of items in the customList, creating the amount of tabs and pages in the Fragments.
In my ChildTabFragment I load a customList on tab selection event,
when I select a Tab in the ParentTabFragment, I call a getTabID() method from the ChildTabFragment and send the id of the Tab due to which I load the customList according to the id in the ParentTabFragment.
Problem is when I swipe or select tabs, duplicate/false data gets created in the customList.
I get the proper Id of the selected tab but when I try to pass it in the method, random id is called.
In my Activity Class:
for (int j =0;j<it.size();j++){
parentTabFragment.addPage(it.get(j).getTabMenuItem(), it.get(j).getTabMenuId() , selectedMenu);
}
ParentTabFragment:
public void addPage(String pagename, String pageId, String selectedMenu) {
Bundle bundle = new Bundle();
bundle.putString("data", pagename);
//bundle.putString("pageID", pageId);
childTabFragment = new ChildTabFragment();
childTabFragment.setArguments(bundle);
adapter.addFrag(childTabFragment, pagename, pageId);
adapter.notifyDataSetChanged();
if (selectedMenu == null) {
viewPager.setCurrentItem(0);
} else {
for (int i = 0; i < tabLayout.getTabCount(); i++) {
if (tabLayout.getTabAt(i).getText().equals(selectedMenu)) {
viewPager.setCurrentItem(i);
}
}
}
if (adapter.getCount() > 0) tabLayout.setupWithViewPager(viewPager);
setupTabLayout();
}
public void setupTabLayout() {
selectedTabPosition = viewPager.getCurrentItem();
for (int i = 0; i < tabLayout.getTabCount(); i++) {
tabLayout.getTabAt(i).setCustomView(adapter.getTabView(i));
}
}
ChildTabFragment:
public class ChildTabFragment extends Fragment {
String childname;
int menuItemId;
TextView textViewChildName, txtViewItemId;
ListView childTabMenuList;
private ArrayList<ChildTabMenu_POJO> childTabMenuPojoList = new ArrayList<>();
private ListView listView;
private ChildTabMenuAdapter childTabMenuAdapter;
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.child_tab_fragment, container, false);
Bundle bundle = getArguments();
childname = bundle.getString("data");
getIDs(view);
return view;
}
private void getIDs(View view) {
childTabMenuList = (ListView) view.findViewById(R.id.childTabMenuList);
loadChildMenu();
}
private void loadChildMenu(menuItemId) {
ChildTabMenu_POJO menu_pojo4 = new ChildTabMenu_POJO(String.valueOf(menuItemId), "4");
childTabMenuPojoList.add(menu_pojo4);
childTabMenuAdapter = new ChildTabMenuAdapter(childTabMenuPojoList, getActivity());
childTabMenuList.setAdapter(childTabMenuAdapter);
}
public void getTabID(int tabId) {
menuItemId = tabId;
Log.e("updatefrag", String.valueOf(menuItemId));
}
}
ViewPagerAdapter:
public class ViewPagerAdapter extends FragmentStatePagerAdapter {
private final ArrayList<Fragment> mFragmentList = new ArrayList<>();
private final ArrayList<Adapter_POJO> mFragmentTitleList = new ArrayList<>();
Context context;
ViewPager viewPager;
TabLayout tabLayout;
Adapter_POJO adapter_pojo;
public ViewPagerAdapter(FragmentManager manager, Context context, ViewPager viewPager,
TabLayout tabLayout) {
super(manager);
this.context = context;
this.viewPager = viewPager;
this.tabLayout = tabLayout;
}
#Override
public Fragment getItem(int position) {
return mFragmentList.get(position);
}
#Override
public int getCount() {
return mFragmentList.size();
}
public int getItemCount() {
return mFragmentTitleList.size();
}
public void addFrag(Fragment fragment, String title, String pageId) {
mFragmentList.add(fragment);
adapter_pojo = new Adapter_POJO(title,pageId);
mFragmentTitleList.add(adapter_pojo);
}
public View getTabView(final int position) {
View view = LayoutInflater.from(context).inflate(R.layout.view_pager_adapter_layout, null);
TextView tabItemName = (TextView) view.findViewById(R.id.textViewTabItemName);
tabItemName.setText(mFragmentTitleList.get(position).adapterMenuItem);
tabItemName.setTextColor(context.getResources().getColor(android.R.color.background_light));
return view;
}
#Override
public int getItemPosition(Object object) {
return POSITION_NONE;
}
#Override
public CharSequence getPageTitle(int position) {
return mFragmentTitleList.get(position).adapterMenuItem;
}
public String getPageId(int position){
return mFragmentTitleList.get(position).adapterMenuId;
}
}

If i understand your question so you need to create newInstance constructor for creating fragment with arguments
public static ChildTabFragment newInstance(int page, String title) {
FirstFragment fragmentFirst = new FirstFragment();
Bundle args = new Bundle();
args.putInt("someInt", page);
args.putString("someTitle", title);
fragmentFirst.setArguments(args);
return fragmentFirst;
}
And Store instance variables based on arguments passed in your ChildTabFragment .
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
page = getArguments().getInt("someInt", 0);
title = getArguments().getString("someTitle");
}
And now update the view in your onCreateView method
TextView tvLabel = (TextView) view.findViewById(R.id.tvLabel);
tvLabel.setText(page + " -- " + title);
And the main thing you should returns the ChildTabFragment to display for that page from your ViewPagerAdapter like this.
#Override
public Fragment getItem(int position) {
return ChildTabFragment.newInstance(position,"page "+String.valueOf(position));
}

Passing data between two Fragments: NullPointerException

I'm having an Activity that hosts two Fragments. One which contains an EditText and one that shows the input in a GridView. Fragment1 implements an interface to notify when the user wants to save the input. In the Activity I want to pass the data to the ArrayAdapter of Fragment2 but here I get the NullPointerException.
Activity:
public class SwipeTest extends FragmentActivity implements TestFragment1
.OnFragmentInteractionListener {
private final String[] tabs = {"Test 1", "Test 2"};
private ViewPager pager;
private ActionBar actionBar;
private TabsPagerAdapter adapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.pager = new ViewPager(this);
ViewGroup.LayoutParams params = new ViewGroup.LayoutParams(ViewGroup
.LayoutParams.MATCH_PARENT,
ViewGroup
.LayoutParams.MATCH_PARENT);
this.pager.setLayoutParams(params);
setContentView(this.pager);
this.actionBar = getActionBar();
this.adapter = new TabsPagerAdapter(
getSupportFragmentManager());
this.pager.setAdapter(this.adapter);
this.actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
setUpViewPager();
setUpActionBar();
}
/**
* Sets up the ViewPager and adds an OnPageChangeListener
*/
private void setUpViewPager() {
this.pager.setAdapter(this.adapter);
// pager needs an id; crashes if it has none
this.pager.setId(123456789);
// Set up the listener
ViewPager.OnPageChangeListener onPageChangeListener = new ViewPager
.OnPageChangeListener() {
#Override
public void onPageScrolled(int i, float v, int i2) {
}
#Override
public void onPageSelected(int i) {
SwipeTest.this.actionBar.setSelectedNavigationItem(i);
}
#Override
public void onPageScrollStateChanged(int i) {
}
};
this.pager.setOnPageChangeListener(onPageChangeListener);
}
/**
* Sets up the ActionBar with it's tabs and adds an ActionBar.TabListener to
* them
*/
private void setUpActionBar() {
this.actionBar = getActionBar();
this.actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
// Set up listener
ActionBar.TabListener tabListener = new ActionBar.TabListener() {
#Override
public void onTabSelected(ActionBar.Tab tab,
FragmentTransaction
fragmentTransaction) {
SwipeTest.this.pager.setCurrentItem(tab.getPosition());
}
#Override
public void onTabUnselected(ActionBar.Tab tab,
FragmentTransaction
fragmentTransaction) {
}
#Override
public void onTabReselected(ActionBar.Tab tab,
FragmentTransaction
fragmentTransaction) {
}
};
for (String tab_name : this.tabs) {
this.actionBar.addTab(
this.actionBar.newTab()
.setText(tab_name)
.setTabListener(tabListener));
}
}
/**
* Interface method of Fragment1
*/
#Override
public void onFragmentInteraction(String s) {
// This gets the fragment correct
TestFragment2 fragment = (TestFragment2) ((TabsPagerAdapter) pager
.getAdapter()).getItem(1);
// This assigns null to adapter
ArrayAdapter<String> adapter = (ArrayAdapter<String>) fragment
.getAdapter();
adapter.add(s);
adapter.notifyDataSetChanged();
}
public class TabsPagerAdapter extends FragmentPagerAdapter {
public TabsPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int index) {
switch (index) {
case 0:
return new TestFragment1();
case 1:
return new TestFragment2();
}
return null;
}
#Override
public int getCount() {
return 2;
}
}
}
Fragment1:
public class TestFragment1 extends Fragment {
private OnFragmentInteractionListener mListener;
private EditText edit;
public TestFragment1() {
// Required empty public constructor
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(
ViewGroup.LayoutParams.MATCH_PARENT,
ViewGroup.LayoutParams.MATCH_PARENT);
LinearLayout layout = new LinearLayout(getActivity());
layout.setLayoutParams(params);
this.edit = new EditText(getActivity());
Button btn = new Button(getActivity());
btn.setText("Save");
btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
onButtonPressed();
}
});
layout.addView(this.edit);
layout.addView(btn);
return layout;
}
public void onButtonPressed() {
if (this.mListener != null) {
String input = this.edit.getText().toString();
this.mListener.onFragmentInteraction(input);
}
}
#Override
public void onAttach(Activity activity) {
super.onAttach(activity);
try {
this.mListener = (OnFragmentInteractionListener) activity;
} catch (ClassCastException e) {
throw new ClassCastException(activity.toString()
+ " must implement " +
"OnFragmentInteractionListener");
}
}
#Override
public void onDetach() {
super.onDetach();
this.mListener = null;
}
public interface OnFragmentInteractionListener {
public void onFragmentInteraction(String s);
}
}
Fragment2:
public class TestFragment2 extends Fragment {
private final List<String> data = new ArrayList<String>();
private ArrayAdapter<String> adapter;
public TestFragment2() {
// Required empty public constructor
}
public ArrayAdapter getAdapter() {
return this.adapter;
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
GridView view = new GridView(getActivity());
GridView.LayoutParams params = new AbsListView.LayoutParams(
ViewGroup.LayoutParams.MATCH_PARENT,
ViewGroup.LayoutParams.MATCH_PARENT);
view.setLayoutParams(params);
this.data.add("Hello");
this.data.add("World");
this.adapter = new ArrayAdapter(getActivity(),
android.R.layout
.simple_list_item_1,
this.data);
view.setAdapter(this.adapter);
return view;
}
}
I don't know why ArrayAdapter<String> adapter = (ArrayAdapter<String>) fragment.getAdapter(); is null. So, how do I get access to the fields of Fragment2?

It seems problem about lifecycle. As you may know, onCreateView() is async method, so fragment instance could be accessed before setAdapter().
My suggestion is to create TestFragment2 instance in SwipeTest#onCreate(). Also, your code creates new instance every time button pressed. It seems not good idea.

The problem was within the PagerAdapter. I used getItem() to recieve the Fragment which is bound to the tab's position. The mistake was that I returned a new instance of that Fragment instead of returning the existing Fragment. Since that new Fragment has never been shown the Fragment's onCreateView() and hence setUpAdapter() has never been called. That's why I recieved NPE in
ArrayAdapter<String> adapter = (ArrayAdapter<String>) fragment
.getAdapter();
adapter.add(s);
Approach[*]:
public class TabsPagerAdapter extends FragmentPagerAdapter {
private final List<Fragment> mFragments = new ArrayList<Fragment>();
public TabsPagerAdapter(FragmentManager fm) {
super(fm);
mFragments.add(0, new TestFragment1());
mFragments.add(1, new TestFragment2());
}
#Override
public Fragment getItem(int index) {
if (index > (mFragments.size() - 1) )
return null;
return mFragments.get(index);
}
#Override
public int getCount() {
return mFragments.size();
}
}
[*] Untested since I changed my code and don't use the PagerAdapter anymore but I think the solution is comprehensible.

If the pager has never shown the second fragment, when your fragment1 interface callback is called the pager returns null:
// This gets the fragment correct
TestFragment2 fragment = (TestFragment2) ((TabsPagerAdapter) pager
.getAdapter()).getItem(1);
So your subsequent call to getAdapter() will result in the NPE.

viewpager with images works but on back button images don't show

I have a viewpager with image fragments in it that works but on back was getting an error saying that there is no empty constructor. I made one but now my images don't show up because imageResourceId is null. I've tried a million things and can't figure it out.
public final class TestFragment extends Fragment {
String imageResourceId;
public TestFragment() {
}
public TestFragment(String cONTENT) {
imageResourceId = cONTENT;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
ImageView image = new ImageView(getActivity());
new DownloadImageTask((ImageView) image).execute(imageResourceId);
LinearLayout layout = new LinearLayout(getActivity());
layout.setGravity(Gravity.CENTER);
layout.addView(image);
return layout;
}
}
class TestFragmentAdapter extends FragmentPagerAdapter implements
IconPagerAdapter {
public String[] CONTENT;
private int mCount;
protected static final int[] ICONS = new int[] {
R.drawable.perm_group_calendar, R.drawable.perm_group_camera,
R.drawable.perm_group_device_alarms, R.drawable.perm_group_location };
public TestFragmentAdapter(FragmentManager fm, JSONArray photoData) {
super(fm);
// photoData = (JSONArray) userProfile.get("photos");
CONTENT = new String[photoData.length()];
mCount = photoData.length();
for (int i = 0; i < photoData.length(); i++) {
JSONObject mainPhoto;
try {
mainPhoto = photoData.getJSONObject(i);
CONTENT[i] = mainPhoto.getString("src_big");
} catch (JSONException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
}
notifyDataSetChanged();
}
#Override
public Fragment getItem(int position) {
return new TestFragment(CONTENT[position]);
}
#Override
public int getCount() {
return mCount;
}
#Override
public int getIconResId(int index) {
return ICONS[index % ICONS.length];
}
public void setCount(int count) {
if (count > 0 && count <= 10) {
mCount = count;
notifyDataSetChanged();
}
}
in the activity
mAdapter = new TestFragmentAdapter(
getSupportFragmentManager(), photoData);
mPager = (ViewPager) findViewById(R.id.pager);
mPager.setAdapter(mAdapter);
mIndicator = (LinePageIndicator) findViewById(R.id.indicator);
mIndicator.setViewPager(mPager);

Android uses the empty constructor of a fragment to restore the fragment when there is a configuration change, that's why you can't modify it, and you can't override it because you get an error in eclipse. The best practice to pass arguments to a fragment, when instantiating it, is to use an static factory method:
public class TestFragment extends Fragment {
String imageResourceId;
public static TestFragment newInstance(String resource) {
TestFragment f = new TestFragment();
Bundle args = new Bundle();
args.putString("Resource", resource);
f.setArguments(args);
return f;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
imageResourceId = getArguments().getString("Resource");
}
}
To instanciate it you use the static method:
TestFragment fragment = TestFragment.newInstance("some string");

listview item onclick into pageview in next activity

I have a listview containing item apple, banana, orange ...in second screen activity
when i click on particular item on apple it navigates to Details screen
here output has to appear like apple ..if i swipe page then banana and for nextswipe orage
apple-->banana-->orange
but am getting output like apple-->apple-->apple.
Intent detailIntent =new Intent(SecondScreen.this, Details.class);
startActivity(detailIntent);
public class MyApplication extends Application {
ArrayList<String> totalvalue = new ArrayList<String>();
}
public class Details extends FragmentActivity{
MyApplication app;
ViewPager pager;
MyFragmentPagerAdapter pagerAdapter;
public static int position ;
#Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.detail);
app = ((MyApplication) getApplicationContext());
pager = (ViewPager) findViewById(R.id.pager);
FragmentManager fm = getSupportFragmentManager();
pagerAdapter = new MyFragmentPagerAdapter(fm,app.totalvalue);
pager.setAdapter(pagerAdapter);
}
public static class MyFragmentPagerAdapter extends FragmentPagerAdapter {
private static ArrayList<String> temperList;
public MyFragmentPagerAdapter(FragmentManager fm, ArrayList<String> totalvalue ) {
super(fm);
this.temperList = totalvalue;
}
public Fragment getItem(int position) {
return ThingFragment.newInstance((temperList.get(position)));
}
#Override
public int getCount(){
return temperList.size();
}
private static class ThingFragment extends Fragment {
private String name1;
static ThingFragment newInstance(String string ) {
ThingFragment f = new ThingFragment();
Bundle args = new Bundle();
args.putString("name",temperList.get(position) );
f.setArguments(args);
return f;
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
name1 = getArguments().getString("name");
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.myfragment_layout, container, false);
TextView t = (TextView)v.findViewById(R.id.prodcutt);
t.setText(""+ name1);
return v;
}
}
}
}

args.putString("name",temperList.get(position) ); shouldn't be possible inside your ThingFragment as its static.
That should be args.putString("name",string);
Also your temperList shouldn't be static in your adapter (no reason to, your passing it as a param) just make it final - private final ArrayList<String> temperList;
If that doesn't fix it please post more structured separated code so we can see how your application is built up a bit more. The adapter looks fine, so it maybe a case that your writing/overwriting the array at some point.