I just wanna know if I'm doing something wrong since I'm kinda new to all this.
If there is anything else that you'll like me to add just let me know.
This is the repo branch where I'm trying to implement the ViewPager if you wanna see all the code.
Context
So I have 4 Categories represented with Fragments, each of this categories holds an ArrayList of items that each has a onItemClickListener that should reproduce some audio.
I'm trying to display the Fragments with a ViewPager but the problem is that when I scroll from a Fragment to another, then come back to the already created Fragment, it doesnt register the touch event, nothing happens, not even an error nor exception.
If I go to a newly created Fragment the touch works just fine.
Also, after switching back to an already created Fragment if I scroll even just a little bit to another Fragment and comeback or through the ArrayList of that Fragment for some reason it starts to recognize the touch in the ArrayList items again.
Similar questions that didn't really help
Fragments in ViewPager2 does not respond to clicks if scroll position is 0
ViewPager2 conflicting with SwipeRefreshLayout
Android ViewPager2 with fragment containing a recyclerview not scrolling
What I've tried
I tried to use a coordinatorlayout wrapping the ViewPager2 but there is no difference
I've been reading some of the official viewPager2 examples that are written in Kotlin but none of them seem to have a similar situation (also it's hard for me to read Kotlin code)
Code Snippets
word_list.xml:
<ListView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/root_list_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#color/tan_background" />
activity_main.xml:
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="MainActivity">
<androidx.viewpager2.widget.ViewPager2
android:id="#+id/viewpager"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal"/>
</FrameLayout>
This is one of the Fragments, the other three are basically the same, just the items in the arrayList change and some other minor things:
// ...Skipped some irrelevant code...
public class NumbersFragment extends Fragment {
private ArrayList<Word> mWords;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View rootView = inflater.inflate(R.layout.word_list, container, false);
mWords = new ArrayList<>();
// ...Add all the items to the list...
// Make the adapter for the word items
WordAdapter adapter = new WordAdapter(getActivity(), mWords, R.color.category_numbers);
// Find the root view of the list
ListView listView = rootView.findViewById(R.id.root_list_view);
// Add adapter to the root list view
listView.setAdapter(adapter);
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Log.d("NumbersFragment", "CLICKED");
}
}
});
return rootView;
}
#Override
public void onPause() {
super.onPause();
Log.d("NumbersFragment", "Fragment paused");
}
}
This is the Category adapter, it manages the fragments:
public class CategoryAdapter extends FragmentStateAdapter {
private static final int NUM_CATEGORIES = 4;
// Required public constructor
public CategoryAdapter(#NonNull FragmentActivity fragmentActivity) {
super(fragmentActivity);
}
#NonNull
#Override
public Fragment createFragment(int position) {
// Depending on which page the user is in,
// create a fragment of the corresponding category
switch (position) {
case 0:
return new NumbersFragment();
case 1:
return new FamilyFragment();
case 2:
return new ColorsFragment();
default:
return new PhrasesFragment();
}
}
#Override
public int getItemCount() {
return NUM_CATEGORIES;
}
}
And this is my MainActivity:
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Set the content of the activity to use the activity_main.xml layout file
setContentView(R.layout.activity_main);
// Find the view pager that will allow the user to swipe between fragments
ViewPager2 viewPager = findViewById(R.id.viewpager);
// Create an adapter that knows which fragment should be shown on each page
CategoryAdapter adapter = new CategoryAdapter(this);
//or CategoryAdapter adapter = new CategoryAdapter(getSupportFragmentManager(), getLifecycle());
// Set the adapter into the view pager
viewPager.setAdapter(adapter);
}
}
add this in your MainActivity viewPager.setOffscreenPageLimit(3); after creating viewpager
It’s because the ViewPager has a default offscreen limit of 1 ,and ViewPager2 has a default offscreen limit of 0.
In ViewPager2 when you switch tabs the previous tab will be automatically refreshed.
in ViewPager if you have 3 tabs or more when you switch to 3rd tab automatically first one will be destroyed and when you goes to 1st tab it will be recreated.
viewPager.setOffscreenPageLimit(3); from this line when you switch to a tab,the previous 3 tabs will be preloaded and next 3 tabs will be preloaded so nothing will be refreshed.
Related
I am working on my first rather big project in android studio and I've been struggling for the past three days with this:
My app has a bottom navigation component that opens 3 other fragments and I was wondering how I could implement a ListView into one of those 3 fragments. I managed to put the ListView in the main layout (activity_main.xml), but as soon as I put the ListView into a layout that's not the main layout I get an NPE. I guess that's because if I try to link the ListView to its data with findViewById(R.id.ListView) it's looking for ListView in activity_main. The code that tries to link the ListView to the component in the layout-file is written in the onCreate in the mainActivity.java. How can I tell the programm to look for the ListView in layout_With_List.xml?
I read on another question that I need to change the setContentView(R.layout.activity_main) in onCreate to setContentView(R.layout.layout_With_List), but that just creates another error.
So how can I properly put a ListView into another fragment, so it won't float around in the main layout when I change tabs with the bottom navigation AND make it display data?
The error i'm getting:
Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference
This is the Relevant code bits:
MainActivity.java
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
lv_productlist = findViewById(R.id.lv_productlist);
showFoodOnListView(db_helper);
}
The code that passes data to the ListView:
private void showFoodOnListView(DB_Helper db_helper2) {
food_ArrayAdapter = new ArrayAdapter<Product_Model>(MainActivity.this, android.R.layout.simple_list_item_1, db_helper2.getEveryone());
lv_productlist.setAdapter(food_ArrayAdapter);
}
layout_With_List.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.recyclerview.widget.RecyclerView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/lv_productlist"
android:name="com.ocdm.prepper.ListFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginLeft="16dp"
android:layout_marginRight="16dp"
app:layoutManager="LinearLayoutManager"
tools:context=".ListFragment"
tools:listitem="#layout/fragment_list" />
===========================SOLUTION===============================
Thanks to [https://stackoverflow.com/users/4039784/hayssam-soussi]
I could figure it out.
lv_productlist = (ListView) view.findViewById(R.id.R.id.lv_productlist);
showFoodOnListView(db_helper);
I had to move the code above into the Layouts corresponding java class, e.g fragment_A.java.
Then I had to move the method showFoodOnListView into fragment_A.java
and set the context to getActivity():.
food_ArrayAdapter = new ArrayAdapter<Product_Model>(getActivity(), android.R.layout.simple_list_item_1, db_helper2.getEveryone());
Let's say you need to add the ListView to Fragment A
First you have to create a layout for Fragment A (i.e fragment_a.xml)
Add your ListView to fragment_a.xml
Then your FragmentA.java code should look like this:
public class FragmentA extends Fragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_a, container, false);
// get the reference of ListView
lv_productlist = (ListView) view.findViewById(R.id.lv_productlist);
showFoodOnListView(db_helper);
return view;
}
}
After I take my Photo and Signature, it displays on the ImageView. However, after I swap the tabs the ImageView returns to its default Image. See my screenshot.
There's no problem when it comes to editText the inputted value is still there. However, the ImageView is my problem. What's causing this problem? And how can I fix this?
Code:
public class RegisterUser extends Fragment {
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
View v =inflater.inflate(R.layout.activity_register_user,container,false);
// Setting ViewPager for each Tabs
ViewPager viewPager = (ViewPager) v.findViewById(R.id.viewpager);
setupViewPager(viewPager);
// Set Tabs inside Toolbar
TabLayout tabs = (TabLayout) v.findViewById(R.id.tabs);
tabs.setupWithViewPager(viewPager);
// Create Navigation drawer and inlfate layout
return v;
}
// Add Fragments to Tabs
private void setupViewPager(ViewPager viewPager) {
Adapter adapter = new Adapter(getChildFragmentManager());
adapter.addFragment(new ListContentFragment(), "Info 1");
adapter.addFragment(new TileContentFragment(), "info 2");
adapter.addFragment(new CaptureSignatureActivity(), "info 3");
adapter.addFragment(new CardContentFragment(), "info 4");
viewPager.setAdapter(adapter);
}
static class Adapter extends FragmentPagerAdapter {
private final List<Fragment> mFragmentList = new ArrayList<>();
private final List<String> mFragmentTitleList = new ArrayList<>();
public Adapter(FragmentManager manager) {
super(manager);
}
#Override
public Fragment getItem(int position) {
return mFragmentList.get(position);
}
#Override
public int getCount() {
return mFragmentList.size();
}
public void addFragment(Fragment fragment, String title) {
mFragmentList.add(fragment);
mFragmentTitleList.add(title);
}
#Override
public CharSequence getPageTitle(int position) {
return mFragmentTitleList.get(position);
}
}
}
When you swipe through tabs (Fragments, actually) in a TabLayout, the default behaviour is that the system kills the previous Fragment to free memory and the subsequent Fragment to the current one will be loaded in the memory.
Now, with your code something similar is happening. When you load a photo and a signature in the 3rd tab (CaptureSignatureFragment) and then swipe through the tabs, the CaptureSignatureFragment is killed and thus both the ImageViews have the default images set to them.
If you wish to keep the data in the 3rd tab intact even after changing tabs, you should better set your ViewPager's offscreen limit to 4 (no. of tabs you have) by:
viewPager.setOffscreenPageLimit(4)
Now, changing the tabs won't kill any of the fragments. However, doing this can create performance issues.
I have a fixed tab layout with 3 tabs. I am trying to have a button in tab1 to add items into a listview in tab2 using ArrayList, both of them extends Fragment. The below code works only when the the activity extends Activity. Can anyone help me out with an answer to the fix of the problem.
I did some testing with an independent activity with a button that adds to listview inside that same activity layout, this is the one that works
MainActivty
public class MainActivity extends Activity {
private ListView LView;
ArrayList <String> arrayList = new ArrayList<String>();
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
LView = (ListView) findViewById(R.id.listview);
}
public void sendToListView(View view) {
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, arrayList); //Sets the adapter to hold the List View
LView.setAdapter(adapter); //Adds to the List View
arrayList.add("Thursday");
}
}
activity_main
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
<ListView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/listview"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="#+id/button"/>
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="add"
android:onClick="sendToListView"
android:id="#+id/button"/>
</RelativeLayout>
This MainActivity extends Fragment and has an error when i try to implement the same operation
public class MainActivity extends Fragment implements View.OnClickListener {
private ListView LView;
ArrayList <String> arrayList = new ArrayList<String>();
#Override
public View onCreateView(LayoutInflater inflater,
ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.activity_main,
container, false);
LView = (ListView) view.findViewById(R.id.listview);
return view;
}
#Override
public void onClick(View v) {
switch (v.getId()){
case R.id.button:
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, arrayList); //Here is the error
LView.setAdapter(adapter); //Adds to the List View
arrayList.add("Thursday");
break;
}
}
}
How can i get this working for Fragments, and how could i hve this operation be sent to the other Fragment activity tab and saved to SharedPreferences
I think it may have more to do with just your general methodology in your fragments. In your activity, you are using the XML to specify a method to run on click of a Button, which makes a whole lot of sense. In the fragment instead you are overriding the method onClick but not activating it by any means. Instead I would again define a button in your fragment XML and either findViewById in your fragment and add your on click method there instead of how you are currently doing it. Alternatively you could just add a onclick handler to the view inside of your fragment if you do indeed want the user to be able to click anywhere in your fragment.
Button yourFragmentButton = (Button) findViewById(R.id.yourFragementButtonId);
yourFragmentButton.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, arrayList);
//Sets the adapter to hold the List View
LView.setAdapter(adapter); //Adds to the List View
arrayList.add("Thursday");
}
});
You're confunsing the concepts of Activity and Fragment. Having a Fragment does not exclude the necessity for an underlying Activity, because every Fragment needs to be plugged on an Activity to be displayed as it is stated in the AndroidDevelopers:
A Fragment represents a behavior or a portion of user interface in an Activity
To see more on this: http://developer.android.com/guide/components/fragments.html .
But, even considering that you attached the fragment correctly and that you are using the right layout on it, you still need to do a few changes if you need to use a fragment here:
public class MyFragment extends Fragment implements View.OnClickListener {
private ListView LView;
ArrayList <String> arrayList = new ArrayList<String>();
#Override
public View onCreateView(LayoutInflater inflater,
ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.activity_main,
container, false);
LView = (ListView) view.findViewById(R.id.listview);
Button myButton = view.findViewById(R.id.button);
myButton.setOnClickListener(this);
return view;
}
#Override
public void onClick(View v) {
switch (v.getId()){
case R.id.button:
ArrayAdapter<String> adapter = new ArrayAdapter<String>(getContext(), android.R.layout.simple_list_item_1, arrayList); //Here is the error
LView.setAdapter(adapter); //Adds to the List View
arrayList.add("Thursday");
break;
}
}
I keep having an issue with my android app where it is crashing with the following error when swiping between tabs:
09-16 16:19:27.142 4750-4750/com.khackett.runmate E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.khackett.runmate, PID: 4750
java.lang.IllegalStateException: Content view not yet created
at android.support.v4.app.ListFragment.ensureList(ListFragment.java:328)
at android.support.v4.app.ListFragment.getListView(ListFragment.java:222)
at com.khackett.runmate.ui.MyRunsFragment$1.done(MyRunsFragment.java:167)
at com.khackett.runmate.ui.MyRunsFragment$1.done(MyRunsFragment.java:135)
at com.parse.ParseTaskUtils$2$1.run(ParseTaskUtils.java:115)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
This is the MyRunsFragment:
public class MyRunsFragment extends ListFragment {
protected SwipeRefreshLayout mSwipeRefreshLayout;
// member variable to store the list of routes the user has accepted
protected List<ParseObject> mAcceptedRoutes;
private int MY_STATUS_CODE = 1111;
// Default constructor for MyRunsFragment
public MyRunsFragment() {
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_my_runs, container, false);
// Set SwipeRefreshLayout component
mSwipeRefreshLayout = (SwipeRefreshLayout) rootView.findViewById(R.id.swipeRefreshLayout);
// Set the onRefreshListener
mSwipeRefreshLayout.setOnRefreshListener(mOnRefreshListener);
mSwipeRefreshLayout.setColorSchemeResources(
R.color.swipeRefresh1,
R.color.swipeRefresh2,
R.color.swipeRefresh3,
R.color.swipeRefresh4);
return rootView;
}
#Override
public void onViewCreated(View view, Bundle savedInstanceState) {
// Retrieve the accepted routes from the Parse backend
retrieveAcceptedRoutes();
}
#Override
public void onResume() {
super.onResume();
}
#Override
public void onListItemClick(ListView l, View v, int position, long id) {
super.onListItemClick(l, v, position, id);
// create the message object which is set to the message at the current position
ParseObject route = mAcceptedRoutes.get(position);
// String messageType = message.getString(ParseConstants.KEY_FILE_TYPE);
JSONArray parseList = route.getJSONArray(ParseConstants.KEY_LATLNG_POINTS);
JSONArray parseListBounds = route.getJSONArray(ParseConstants.KEY_LATLNG_BOUNDARY_POINTS);
String objectId = route.getObjectId();
String routeName = route.getString(ParseConstants.KEY_ROUTE_NAME);
// JSONArray ids = route.getJSONArray(ParseConstants.KEY_RECIPIENT_IDS);
// Start a map activity to display the route
Intent intent = new Intent(getActivity(), MapsActivityTrackRun.class);
intent.putExtra("parseLatLngList", parseList.toString());
intent.putExtra("parseLatLngBoundsList", parseListBounds.toString());
intent.putExtra("myRunsObjectId", objectId);
intent.putExtra("myRunsRouteName", routeName);
// Start the MapsActivityDisplayRoute activity
startActivityForResult(intent, MY_STATUS_CODE);
}
#Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
}
private void retrieveAcceptedRoutes() {
// query the routes class/table in parse
// get messages where the logged in user ID is in the list of the recipient ID's (we only want to retrieve the messages sent to us)
// querying the message class is similar to how we have been querying users
ParseQuery<ParseObject> queryRoute = new ParseQuery<ParseObject>(ParseConstants.CLASS_ROUTES);
// use the 'where' clause to search through the messages to find where our user ID is one of the recipients
queryRoute.whereEqualTo(ParseConstants.KEY_ACCEPTED_RECIPIENT_IDS, ParseUser.getCurrentUser().getObjectId());
// order results so that most recent message are at the top of the inbox
queryRoute.addDescendingOrder(ParseConstants.KEY_CREATED_AT);
// query is ready - run it
queryRoute.findInBackground(new FindCallback<ParseObject>() {
// When the retrieval is done from the Parse query, the done() callback method is called
#Override
public void done(List<ParseObject> routes, ParseException e) {
// dismiss the progress indicator here
// getActivity().setProgressBarIndeterminateVisibility(false);
// End refreshing once routes are retrieved
// done() is called from onResume() and the OnRefreshListener
// Need to check that its called from the the OnRefreshListener before ending it
if (mSwipeRefreshLayout.isRefreshing()) {
mSwipeRefreshLayout.setRefreshing(false);
}
// the list being returned is a list of routes
if (e == null) {
// successful - routes found. They are stored as a list in messages
mAcceptedRoutes = routes;
// adapt this data for the list view, showing the senders name
// create an array of strings to store the usernames and set the size equal to that of the list returned
String[] usernames = new String[mAcceptedRoutes.size()];
// enhanced for loop to go through the list of users and create an array of usernames
int i = 0;
for (ParseObject message : mAcceptedRoutes) {
// get the specific key
usernames[i] = message.getString(ParseConstants.KEY_SENDER_NAME);
i++;
}
// Create the adapter once and update its state on each refresh
if (getListView().getAdapter() == null) {
// the above adapter code is now replaced with the following line
RouteMessageAdapter adapter = new RouteMessageAdapter(getListView().getContext(), mAcceptedRoutes);
// Force a refresh of the list once data has changed
adapter.notifyDataSetChanged();
// need to call setListAdapter for this activity. This method is specifically from the ListActivity class
setListAdapter(adapter);
} else {
// refill the adapter
// cast it to RouteMessageAdapter
((RouteMessageAdapter) getListView().getAdapter()).refill(mAcceptedRoutes);
}
}
}
});
}
protected SwipeRefreshLayout.OnRefreshListener mOnRefreshListener = new SwipeRefreshLayout.OnRefreshListener() {
#Override
public void onRefresh() {
// When list is swiped down to refresh, retrieve the users runs from the Parse backend
retrieveAcceptedRoutes();
}
};
}
And the fragment_my_runs layout file:
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity$PlaceholderFragment">
<android.support.v4.widget.SwipeRefreshLayout
android:id="#+id/swipeRefreshLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_alignParentStart="true"
android:layout_alignParentTop="true">
<ListView
android:id="#android:id/list"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_alignParentStart="true"
android:layout_alignParentTop="true"
android:clipToPadding="false"
android:paddingBottom="#dimen/inbox_vertical_margin"/>
</android.support.v4.widget.SwipeRefreshLayout>
<TextView
android:id="#android:id/empty"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="#string/empty_inbox_label"
android:textSize="#dimen/default_text_size"/>
</RelativeLayout>
The TabFragmentContainer
public class TabFragmentContainer extends Fragment {
// Create the FragmentPagerAdapter that will provide and manage tabs for each section.
public static MyFragmentPagerAdapter myFragmentPagerAdapter;
public static TabLayout tabLayout;
// The ViewPager is a layout widget in which each child view is a separate tab in the layout.
// It will host the section contents.
public static ViewPager viewPager;
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
// Inflate tab_layout_fragment_container view and setup views for the TabLayout and ViewPager items.
View view = inflater.inflate(R.layout.tab_layout_fragment_container, null);
tabLayout = (TabLayout) view.findViewById(R.id.tabs);
// Set up the ViewPager with the sections adapter.
viewPager = (ViewPager) view.findViewById(R.id.viewpager);
// Instantiate the adapter that will return a fragment for each of the three sections of the main activity
myFragmentPagerAdapter = new MyFragmentPagerAdapter(getActivity(), getChildFragmentManager());
// Set up the adapter for the ViewPager
viewPager.setAdapter(myFragmentPagerAdapter);
// Runnable() method required to implement setupWithViewPager() method
tabLayout.post(new Runnable() {
#Override
public void run() {
tabLayout.setupWithViewPager(viewPager);
viewPager.setCurrentItem(1, false);
// tabLayout.getTabAt(1).select();
}
});
// Return the created View
return view;
}
}
The FragmentPagerAdapter:
public class MyFragmentPagerAdapter extends FragmentPagerAdapter {
// The context to be passed in when the adapter is created.
private Context mContext;
// The number of tabs in the layout.
public static int numberOfTabs = 3;
/**
* Default constructor that accepts a FragmentManager parameter to add or remove fragments.
*
* #param context the context from the activity using the adapter.
* #param fragmentManager the FragmentManager for managing Fragments inside of the TabFragmentContainer.
*/
public MyFragmentPagerAdapter(Context context, FragmentManager fragmentManager) {
super(fragmentManager);
mContext = context;
}
/**
* Method to return the relevant fragment for the selected tab.
*/
#Override
public Fragment getItem(int position) {
switch (position) {
case 0:
return new MyRunsFragment();
case 1:
return new InboxRouteFragment();
case 2:
return new FriendsFragment();
}
return null;
}
/**
* Method that gets the number of tabs in the layout.
*
* #return the number of tabs in the layout.
*/
#Override
public int getCount() {
return numberOfTabs;
}
/**
* Method that returns the title of each tab in the layout.
*/
#Override
public CharSequence getPageTitle(int position) {
Locale locale = Locale.getDefault();
switch (position) {
case 0:
return mContext.getString(R.string.title_section1).toUpperCase(locale);
case 1:
return mContext.getString(R.string.title_section2).toUpperCase(locale);
case 2:
return mContext.getString(R.string.title_section3).toUpperCase(locale);
}
return null;
}
}
The tab_layout_fragment_container file that contains the ViewPager widget:
<?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="wrap_content"
android:orientation="vertical">
<android.support.design.widget.TabLayout
android:id="#+id/tabs"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="#color/ColorPrimaryPurple"
app:tabGravity="fill"
app:tabIndicatorColor="#color/ColorPrimaryPurple"
app:tabMode="fixed"
app:tabSelectedTextColor="#color/textColorPrimary"
app:tabTextColor="#color/pressedPurpleButton">
</android.support.design.widget.TabLayout>
<android.support.v4.view.ViewPager
android:id="#+id/viewpager"
android:layout_width="match_parent"
android:layout_height="match_parent">
</android.support.v4.view.ViewPager>
</LinearLayout>
The onCreate() method in my MainActivity:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Initialise the DrawerLayout and NavigationView views.
mDrawerLayout = (DrawerLayout) findViewById(R.id.drawerLayout);
mNavigationView = (NavigationView) findViewById(R.id.navigationDrawerMenu);
// Inflate the first fragment to be displayed when logged into the app.
mFragmentManager = getSupportFragmentManager();
mFragmentTransaction = mFragmentManager.beginTransaction();
mFragmentTransaction.replace(R.id.containerView, new TabFragmentContainer()).commit();
// Setup click events on the NavigationView items.
// When an item is selected, replace the tab fragment container with the requested fragment.
mNavigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
#Override
public boolean onNavigationItemSelected(MenuItem menuItem) {
mDrawerLayout.closeDrawers();
if (menuItem.getItemId() == R.id.navItemHome) {
FragmentTransaction tabFragmentContainer = mFragmentManager.beginTransaction();
tabFragmentContainer.replace(R.id.containerView, new TabFragmentContainer()).commit();
}
if (menuItem.getItemId() == R.id.navItemRunHistory) {
FragmentTransaction runHistoryFragment = mFragmentManager.beginTransaction();
runHistoryFragment.replace(R.id.containerView, new RunHistoryFragment()).commit();
}
if (menuItem.getItemId() == R.id.navItemSettings) {
FragmentTransaction settingsFragment = mFragmentManager.beginTransaction();
settingsFragment.replace(R.id.containerView, new SettingsFragment()).commit();
}
if (menuItem.getItemId() == R.id.navItemHelp) {
FragmentTransaction instructionsFragment = mFragmentManager.beginTransaction();
instructionsFragment.replace(R.id.containerView, new InstructionsFragment()).commit();
}
if (menuItem.getItemId() == R.id.navItemMyProfile) {
FragmentTransaction myProfileFragment = mFragmentManager.beginTransaction();
myProfileFragment.replace(R.id.containerView, new MyProfileFragment()).commit();
}
if (menuItem.getItemId() == R.id.navItemLogOut) {
// User has selected log out option. Log user out and return to login screen.
ParseUser.logOut();
navigateToLogin();
}
return false;
}
});
// Set up the Toolbar.
setupToolbar();
}
I have followed other answers here and added the getListView() functionality to the onViewCreated() method but the problem still persists... Can anyone point out where I might be going wrong?
Based on these facts:
The exception is thrown because there is no root view yet when done() calls getListView().
done() is called when the query made by retrieveAcceptedRoutes() gets a response.
retrieveAcceptedRoutes is called in multiple places, including the OnRefreshListener mOnRefreshListener, which is registered as the refresh listener in onCreateView() before there is a root view (that is, before onCreateView() returns).
...it is possible for getListView() to be called before there is a root view.
Try moving these 3 statements from onCreateView() to onViewCreated(), so that way the refresh listener can only be called when there is a root view.
// Set SwipeRefreshLayout component
mSwipeRefreshLayout = (SwipeRefreshLayout) rootView.findViewById(R.id.swipeRefreshLayout);
// Set the onRefreshListener
mSwipeRefreshLayout.setOnRefreshListener(mOnRefreshListener);
mSwipeRefreshLayout.setColorSchemeResources(
R.color.swipeRefresh1,
R.color.swipeRefresh2,
R.color.swipeRefresh3,
R.color.swipeRefresh4);
onViewCreated is called immediately after onCreateView, but the super.onViewCreated call is missing, perhaps this is root cause of your issue.
#Override
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState); // add this line back in
// Retrieve the accepted routes from the Parse backend
retrieveAcceptedRoutes();
}
I read your question again then I guess that:
Your ListFragment is destroyed while your background task keeps running. So when it's done, your callback would like to update the ListView which is no longer alive.
Actually, viewPager.setOffscreenPageLimit(3); may do the trick, but it's not a good practice. It forces your ViewPager to create and store more Fragments in memory which is not necessary. You can solve this without doing so.
What you should do: one of the following two practice should be fine, or both:
Destroy your task in your onPause or whatever lifecycle method, before your onDestroyView.
Exclude the code where you update your ListView inside your done() method. Make it a local method where you will check your ListView carefully, and there, you should ask your update process to run on UI thread to avoid any threading problem. Make sure to check if your getView() is not null (but not your getListView(), since it throws Exception if getView() returns null).
I recommend you to use both of them to make sure: your view is still useable and you don't waste your resource when running task in invisible fragment. Don't forget that by default, once your fragment is invisible, it is considered to be destroyed (not always, for example ViewPager keep reference of 2 fragments, but keep in mind that case).
remove all these imports:
import com.yourName.runmate.R;
Then resync your gradle and rebuild your project.
Also see here:
"cannot resolve symbol R" in Android Studio
edit
Your first obvious mistake in your Main is
mFragmentManager = getSupportFragmentManager();
should be:
mFragmentManager = getFragmentManager();
or change your Main activity to:
MainActivity extends FragmentActivity to make use of the support fragment manager.
You have a lot of unnecessary code in your question, majority of comments can be removed and imports for the purpose of this question.
What I have come up with is there is no activity, being used. The ListFragment needs to be attached to an Activity or you are trying to call that activity view before it is created.
java.lang.IllegalStateException: Content view not yet created
at android.support.v4.app.ListFragment.ensureList(ListFragment.java:328)
at android.support.v4.app.ListFragment.getListView(ListFragment.java:222)
If you are using Main, then you are not pulling them together well, from what I can see.
Firstly:
Take everything out of your onCreate and onCreateView (for all fragments) except the view inflater.
Place all the extra code into either onViewCreated or onActivityCreated. That way no methods can be called on a null view, as these are called after it is created.
Secondly, you need to sort out your activities and with what you're exactly trying to achieve.
You want a page viewer and a fragmentlist. The pageviewer needs to be associated with an activity, or activity fragment, not a fragment. Otherwise there is no view to attach the pageviewer pages to.
Use a FragmentActivity not a Fragment. To be the activity you run your ListFragment from.
public class TabFragmentContainer extends FragmentActivity {
MyPageAdapter pageAdapter;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.tab_layout_fragment_container); // change to view layout.
// Instantiate the adapter that will return a fragment for each of the three sections of the main activity
myFragmentPagerAdapter = new MyFragmentPagerAdapter(getFragmentManager(), getFragments());
tabLayout = (TabLayout) view.findViewById(R.id.tabs);
// Set up the ViewPager with the sections adapter.
viewPager = (ViewPager) view.findViewById(R.id.viewpager);
// Set up the adapter for the ViewPager
viewPager.setAdapter(myFragmentPagerAdapter);
}
}
I would suggest putting this into your ListFragment, to ensure your activity is created. You will need to move most of your code from your onCreate methods and put them in onViewCreated or onActivityCreated
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
ArrayAdapter adapter = ArrayAdapter.createFromResource(getActivity(), R.layout.my_listview)layout, android.R.layout.simple_list_item_1);
setListAdapter(adapter);
getListView().setOnItemClickListener(this);
}
This code is just a guide, you'll need to tweak it.
Let me know if this helps.
These Q&As are excellent.
Content view not yet created
android Illegal state exception content view not yet create?
Fragment same principles applies to viewpager fragments ViewPager
Try to declare:
viewPager = (ViewPager) view.findViewById(R.id.viewpager);
viewPager.setAdapter(myFragmentPagerAdapter);
myFragmentPagerAdapter = new MyFragmentPagerAdapter(getActivity(), getChildFragmentManager());
before:
tabLayout = (TabLayout) view.findViewById(R.id.tabs);
tabLayout.post(new Runnable() {
#Override
public void run() {
tabLayout.setupWithViewPager(viewPager);
viewPager.setCurrentItem(1, false);
// tabLayout.getTabAt(1).select();
}
});
// Return the created View
return view;
I have a single activity with a navigation drawer (the basic one provided by Eclipse new app wizard). I have a FrameLayout as a container for the different fragments of the app, which are replaced when selecting an item in the navigation drawer. They are also added to the BackStack.
These fragments contain a LinearLayout, which has some EditTexts and a Button. If the button is pressed, a new LinearLayout is created and a couple TextViews are added to it with the content of the EditTexts. The user can repeat this option more than once, so I cannot tell how many LinearLayouts I'll need, therefore I need to add them programmatically.
One of these fragments xml:
<LinearLayout
android:id="#+id/pen_layout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical" >
<LinearLayout
android:id="#+id/new_pen_layout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="#dimen/activity_vertical_margin"
android:background="#drawable/border"
android:orientation="vertical"
android:paddingBottom="#dimen/home_section_margin_bottom"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/home_section_margin_top" >
<EditText
android:id="#+id/new_pen_round"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:inputType="number"
android:hint="#string/new_pen_round_hint"
android:textSize="#dimen/normal_text_size" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:weightSum="2" >
<Button
android:id="#+id/new_pen_cancel_button"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginRight="#dimen/new_item_button_margin_right"
android:layout_weight="1"
android:background="#drawable/button_bg"
android:paddingBottom="#dimen/new_item_button_padding_bottom"
android:paddingTop="#dimen/new_item_button_padding_top"
android:text="#string/new_item_cancel_button"
android:textSize="#dimen/normal_text_size" />
<Button
android:id="#+id/new_pen_insert_button"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginLeft="#dimen/new_item_button_margin_left"
android:layout_weight="1"
android:background="#drawable/button_bg"
android:paddingBottom="#dimen/new_item_button_padding_bottom"
android:paddingTop="#dimen/new_item_button_padding_top"
android:text="#string/new_pen_insert_button"
android:textSize="#dimen/normal_text_size" />
</LinearLayout>
</LinearLayout>
</LinearLayout>
There are actually many other EditTexts but I removed them here to keep it short, the result is the same. It's java file:
public class PenaltiesFragment extends Fragment {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_penalties, container, false);
Button insertNewPen = (Button) view.findViewById(R.id.new_pen_insert_button);
insertNewPen.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
TextView round = (TextView) getActivity().findViewById(R.id.new_pen_round);
LinearLayout layout = (LinearLayout) getActivity().findViewById(R.id.pen_layout);
int numChilds = layout.getChildCount();
CustomPenaltyLayout penalty = new CustomPenaltyLayout(getActivity(), round.getText());
layout.addView(penalty, numChilds - 1);
}
});
return view;
}
}
I removed some useless methods, which are just the default ones. CustomPenaltyLayoutis a subclass of LinearLayout which I created, it just creates some TextViews and adds them to itself.
Everything works fine here. The user inserts data in the EditText, presses the Insert button and a new layout is created and added in the fragment.
What I want to achieve is: say that I open the navigation drawer and select another page, the fragment gets replaced and if I go back to this fragment (via navigation drawer or via Back button) I want the text, that the user added, to be still there.
I do not call PenaltiesFragment.newInstance() everytime I switch back to this fragment, I instead create the PenaltiesFragment object once and keep using that one. This is what I do:
Fragment fragment;
switch (newContent) {
// various cases
case PEN:
if(penFragment == null) // penFragment is a private field of the Main Activity
penFragment = PenaltiesFragment.newInstance();
fragment = penFragment;
break;
}
getSupportFragmentManager()
.beginTransaction()
.replace(R.id.container, fragment)
.addToBackStack("fragment back")
.commit();
I understand that onCreateView() is called again when the fragment is reloaded, right? So that is probably why a new, blank fragment is what I see. But how do I get the inserted CustomPenaltyLayout back? I cannot create it in the onCreateView() method.
I found a solution to my problem. I replaced the default FrameLayout that Android automatically created as a container for my fragments, with a ViewPager, then created a FragmentPagerAdapter like this:
public static class MyAdapter extends FragmentPagerAdapter {
public MyAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
Fragment fragment;
switch (position) {
// ...other cases
case PEN:
fragment = PenaltiesFragment.newInstance();
break;
// ...other cases
}
return fragment;
}
#Override
public int getCount() {
return 6;
}
}
Then the only thing left to do to keep all the views at all times has been to add this line to my activity onCreate method.
mPager.setOffscreenPageLimit(5);
See the documentation for details on how this method works.
This way, though, I had to reimplement all the back button logic, but it's still simple, and this is how I did it: I create a java.util.Stack<Integer> object, add fragment numbers to it (except when you use the back button, see below), and override onBackPressed() to make it pop the last viewed fragment instead of using the back stack, when my history stack is not empty.
You want to avoid pushing elements on the Stack when you press the back button, otherwise you will get stuck between two fragments if you keep using the back button, instead of eventually exiting.
My code:
MyAdapter mAdapter;
ViewPager mPager;
Stack<Integer> pageHistory;
int currentPage;
boolean saveToHistory;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mAdapter = new MyAdapter(getSupportFragmentManager());
mPager = (ViewPager)findViewById(R.id.container);
mPager.setAdapter(mAdapter);
mPager.setOffscreenPageLimit(5);
pageHistory = new Stack<Integer>();
mPager.setOnPageChangeListener(new OnPageChangeListener() {
#Override
public void onPageSelected(int arg0) {
if(saveToHistory)
pageHistory.push(Integer.valueOf(currentPage));
}
#Override
public void onPageScrolled(int arg0, float arg1, int arg2) {
}
#Override
public void onPageScrollStateChanged(int arg0) {
}
});
saveToHistory = true;
}
#Override
public void onBackPressed() {
if(pageHistory.empty())
super.onBackPressed();
else {
saveToHistory = false;
mPager.setCurrentItem(pageHistory.pop().intValue());
saveToHistory = true;
}
};