I am new to using a ViewPager, but the initial screen on my app is a ListView that the user can add/remove new items to, then clicking on one of the items brings them to a "details" fragment based on an id that is passed. I'd like for the user to also be able to swipe from the listing through to each of the details.
I have the ViewPager working, except the id's are always off by one. This might be my lack of understanding of ViewPagers, but if I put a breakpoint in the onCreateView of the details fragment, the breakpoint is hit when the app loads and the id that is passed is the first id. So, say the ids are 1,2,3,4, when the app loads, the id on app start-up in onCreateView is 1. When I perform the initial swipe from the listing to the first details fragment, the id is 2 (when I would expect it to be 1).
This is what I have so far:
Main.class (this initial activity on app start-up)
public class Main extends SherlockFragmentActivity
{
private static int NUMBER_OF_PAGES;
private ViewPager mViewPager;
private MyFragmentPagerAdapter mMyFragmentPagerAdapter;
private static List<Fragment> fragments;
#Override
public void onCreate(final Bundle icicle)
{
super.onCreate(icicle);
setContentView(R.layout.main);
mViewPager = (ViewPager)findViewById(R.id.viewpager);
mMyFragmentPagerAdapter = new MyFragmentPagerAdapter(getSupportFragmentManager());
mViewPager.setAdapter(mMyFragmentPagerAdapter);
final List<Integer> ids = GetIds(); //loads ids to popular the viewpager
NUMBER_OF_PAGES = ids.size();
fragments = new ArrayList<Fragment>();
fragments.add(new ListingFragment()); //initial screen
for(Integer id : ids)
fragments.add(DetailsFragment.newInstance(id));
}
private static class MyFragmentPagerAdapter extends FragmentStatePagerAdapter {
public MyFragmentPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int index) {
return fragments.get(index);
}
#Override
public int getCount() {
return NUMBER_OF_PAGES;
}
}
}
DetailsFragment.class
public class DetailsFragment extends SherlockFragmentActivity
{
private int detailId;
private List<Integer> items;
#Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
}
#Override
public void onActivityCreated(final Bundle icicle)
{
super.onActivityCreated(icicle);
}
public static DetailsFragment newInstance(int id) {
DetailsFragment lf = new DetailsFragment();
Bundle bundle = new Bundle();
bundle.putInt("id", id);
lf.setArguments(bundle);
return lf;
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.details, container, false);
detailId = getArguments().getInt("id"); //this id is always off
items = GetItems();
return view;
}
}
I have the ViewPager working, except the id's are always off by one.
This might be my lack of understanding of ViewPagers, but if I put a
breakpoint in the onCreateView of the details fragment, the breakpoint
is hit when the app loads and the id that is passed is the first id.
So, say the ids are 1,2,3,4, when the app loads, the id on app
start-up in onCreateView is 1. When I perform the initial swipe from
the listing to the first details fragment, the id is 2 (when I would
expect it to be 1).
Maybe I don't understand the problem you're facing but the code you posted(again, if that is the full code you use(currently it will not compile as your DetailsFragments extends SherlockFragmentActivity (?!))) can't do what you say. The way you setup the fragments will make the them have the proper ids.
What you're seeing it's most likely due to the way the ViewPager works, which can be misleading. When you first start the app you'll see the ListingFragment. Now, the ViewPager, in order to provide a smooth swipe for the user will also load(by default) one additional fragment on each side of the current visible fragment(so when the app starts the ViewPager will load page 0(ListingFragment) and the next(to the right as we don't have anywhere to go left)) page, 1(the DetailsFragment with the id 1). When you swipe from the ListingFragment to the first DetailsFragment(which has the id 1) the ViewPager will automatically create the second DetailsFragment(which has the id 2) in advance(again, in order to be able to swipe right away to it). Now, if you have a Log statement in the onCreateView in the DetailsFragment(to see the id) it's normal that you see the second id as you swipe from the ListingFragment to the first DetailsFragment because that Log will not appear from the first DetailsFragment(with id 1, which is already created) being created, it will appear because the second DetailsFragment(with id 2) is being created in advance.
Also, revise your code, as you introduced a subtle bug. You set the size of the adapter to
NUMBER_OF_PAGES which is initialized with ids.size() but then you add the ListingFragment which will make the DetailsFragment with the last id(from ids) not appear at all.
Related
I'm creating an android quiz application in which I'll be using a viewpager. I've gone through some tutorials in which for each new page a new class is created for fragment/tabs. Now if I want to have total 15 pages, then will I have to create that much classes? Isn't there any other alternative?
Each page in the ViewPager will be a different instance of a Fragment, but there's no requirement that each page be a different class of Fragment.
In an excessively simple application, you could imagine that each page in the ViewPager would just show a different number. You could achieve this by creating a OneFragment class to show "1", a TwoFragment class to show "2", and so on. Or, you could create a single NumberFragment class and use fifteen different instances to show fifteen different numbers:
public class NumberFragment extends Fragment {
public static NumberFragment newInstance(int number) {
Bundle args = new Bundle();
args.putInt("number", number);
NumberFragment fragment = new NumberFragment();
fragment.setArguments(args);
return fragment;
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View root = inflater.inflate(R.layout.number_fragment, container, false);
int number = getArguments().getInt("number");
String numberText = String.valueOf(number);
TextView numberView = root.findViewById(R.id.numberView);
numberView.setText(numberText);
return root;
}
}
With this in place, your FragmentPagerAdapter is incredibly simple:
public class MyAdapter extends FragmentPagerAdapter {
#Override
public Fragment getItem(int position) {
return NumberFragment.newInstance(position);
}
#Override
public int getCount() {
return 15;
}
}
This same concept applies even in more complex applications. As long as each page of the ViewPager has the same structure to its data, you can just create a new instance of a single Fragment class by passing the necessary configuration to newInstance().
You can also mix-and-match this technique with the one where you create a new Fragment subclass for each page. Maybe you want your first and your last pages to be unique, but the thirteen middle pages are all basically the same.
You should create a Fragment for each different page you want to show in the ViewPager. Then you could select each Fragment by the position in the FragmentPagerAdapter.
I have been trying to implement a ViewPager with different fragments.
And the problem is when i run the app, in the ViewPager, out of all the pages, only one page is visible and that page only gets changed when I slide over to the other pages in the ViewPager.
Take a look at my code,(although I checked it many times referring it with online resources).
This is what each of my fragments look like:
public class fragment1 extends Fragment {
/* Variable to store reference to the ACtivity */
Activity mCurrentActivity;
/* Variable storing reference to the ArrayList */
private ArrayList<Word> mDefaultWords;
/**
* THe empty public Constructor
*/
public fragment1(){
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
/** Getting reference to the Activity */
mCurrentActivity = getActivity();
// Populating the ArrayList here
// And later in the onActivityCreated callback I set an adapter on the ArrayList
return inflater.inflate(R.layout.activity_others, container, false);
}
#Override
public void onActivityCreated(Bundle savedStateInstance){
super .onActivityCreated(savedStateInstance);
/**
* Creating {#link ArrayAdapter} to link the {#link String}
* from {#link ArrayList} {#param
*/
MyAdapter adaptItems = new MyAdapter(mCurrentActivity, mDefaultWords);
// Getting the id of the ListView in numberActivity.xml
ListView myList = (ListView) mCurrentActivity.findViewById(R.id.theList);
//Chaning background color
myList.setBackgroundColor(ContextCompat.getColor(getContext(), android.R.color.holo_purple));
// Setting the adapter with the {#link ListView}
myList.setAdapter(adaptItems);
}
}
}
My Activity setting the adapter class extending FragmentPagerAdapter as a private inner class and setting the adapter on the ViewPager.
public class Main2Activity extends AppCompatActivity {
private ViewPager mViewPager;
private FragmentPagerAdapter mFragmentStatePagerAdapter;
private FragmentManager mFragmentManager;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main2);
mFragmentManager = getSupportFragmentManager();
mViewPager = (ViewPager) findViewById(R.id.theViewPager);
mFragmentStatePagerAdapter = new MyFragmentStatePagerAdapter(mFragmentManager);
/* Setting the apdapter on the pager */
mViewPager.setAdapter(mFragmentStatePagerAdapter);
}
public class MyFragmentStatePagerAdapter extends FragmentPagerAdapter {
public MyFragmentStatePagerAdapter(FragmentManager fragmentManager){
super(fragmentManager);
}
#Override
public int getCount(){
return 4;
}
#Override
public Fragment getItem(int position) {
if (position == 0) {
return new fragment1();
} else if (position == 1){
return new fragment2();
} else if (position == 2) {
return new fragment3();
} else {
return new fragment4();
}
}
}
}
And here is the layout with the ViewPager
<android.support.v4.view.ViewPager
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/theViewPager"
android:visibility="visible" />
As I said, when I run the app only one page gets displayed, other pages are present in the ViewPager but they are blank and displays the default background color,
And the one page that is displayed is the one that gets changed when I swipe left or right in the ViewPager.
So what's the issue?
dont downvote the question, its a genuine problem.
So, I worked my way around, let me say how.
What happened is, I was working on a cloned project that had a old gradle version and sdktools version was also not updated and was quite old.
and the min API targetted was API 15
And I was testing my application on API 21.
So, what I did is I used a different layouts for each of my fragments.
That is for each fragment I created its own XML layout.
And that worked perfectly.
Odd problem, so I updated the gradle and sdktools, to avoid such weird problems.
I am using a ViewPager to show 9 fragments. In each of these fragments, I want to just show a different picture. I want to use one single fragment layout, but dynamically add in the picture. Also, would like add a "Continue" button on the last fragment that when pressed will go to another activity.
How do I go about making a fragment layout dynamic?
Main Activity
public class StoryboardPageActivity extends FragmentActivity {
// The number of pages (wizard steps) to show in this demo.
private static final int NUM_PAGES = 9;
// The pager widget, which handles animation and allows swiping horizontally to access previous and next wizard steps.
private ViewPager mPager;
// The pager adapter, which provides the pages to the view pager widget.
private PagerAdapter mPagerAdapter;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_storyboard_page);
// Instantiate a ViewPager and a PagerAdapter.
mPager = (ViewPager) findViewById(R.id.storyboardPager);
mPagerAdapter = new StoryboardPagerAdapter(getSupportFragmentManager());
mPager.setAdapter(mPagerAdapter);
}
#Override
public void onBackPressed() {
if (mPager.getCurrentItem() == 0) {
// If the user is currently looking at the first step, allow the system to handle the
// Back button. This calls finish() on this activity and pops the back stack.
super.onBackPressed();
} else {
// Otherwise, select the previous step.
mPager.setCurrentItem(mPager.getCurrentItem() - 1);
}
}
// A simple pager adapter that represents 5 fragment objects, in sequence.
private class StoryboardPagerAdapter extends FragmentStatePagerAdapter {
public StoryboardPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public Fragment getItem(int position) {
return StoryboardFragment.newInstance(position);
}
#Override
public int getCount() {
return NUM_PAGES;
}
}
}
Fragment
public class StoryboardFragment extends Fragment {
private static final String KEY_POSITION = "position";
static StoryboardFragment newInstance(int position) {
StoryboardFragment frag = new StoryboardFragment();
Bundle args = new Bundle();
args.putInt(KEY_POSITION, position);
frag.setArguments(args);
return(frag);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
ViewGroup rootView = (ViewGroup) inflater.inflate(R.layout.fragment_storyboard_page, container, false);
ImageView image = (ImageView)rootView.findViewById(R.id.imgStoryboard);
int position = getArguments().getInt(KEY_POSITION, -1);
int[] images = {R.drawable.storyboard1, R.drawable.storyboard2, R.drawable.storyboard3,
R.drawable.storyboard4, R.drawable.storyboard5, R.drawable.storyboard6,
R.drawable.storyboard7, R.drawable.storyboard8, R.drawable.storyboard9};
image.setImageResource(images[position]);
return rootView;
}
}
Fragment XML
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#fff" >
<ImageView
android:id="#+id/imgStoryboard"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:contentDescription="#string/storyboardSlide" />
</RelativeLayout>
How do I go about making a fragment layout dynamic?
The same way you make any other "layout dynamic". If you want to put an image in an ImageView, call setImageBitmap() or setImageDrawable() or whatever. For example, the PagerAdapter could supply the position to the fragment (via a factory method), and the fragment could then know what image to load.
This sample project demonstrates populating the hint of an EditText with a custom value based upon the page's position.
With respect to the "Continue" button, either have a separate fragment class for that (and appropriate smarts in your PagerAdapter, or always have the button in your layout, but set to android:visibility="gone" by default, toggling it via setVisibility(View.VISIBLE) for the fragment that needs it.
I have a FragmentPagerAdapter for a viewPager Which initially has only one Fragment in it. I want to dynamically add a new Fragment to the adapter when user swipes from right to left, and dynamically remove a Fragment when user swipes from left to right.I have tried to use this library https://github.com/commonsguy/cwac-pager but in that library we have an option to add and remove fragments on button clicks. I have tried to add a OnPageChangeListener to the viewpager but the callback methods ( onPageScrolled and onPageScrollStateChanged) are being called more than once which results in addition of more than one fragment to the FragmentPagerAdapter. So please shed some light on how to do this.
#dora: i think in your case FragmentStatePagerAdapter will help you. I have mentioned its use below as per my understanding.I hope it will help you in taking decision.
There are two ways to implement ViewPager:
• FragmentStatePagerAdapter
• FragmentPagerAdapter
FragmentStatePagerAdapter class consumes less memory, because it destroys fragments, as soon as they are not visible to user, keeping only saved state of that fragment
FragmentPagerAdapter: when there are less number of fragments. But using AndroidFragmentPagerAdapter for large number of fragments would result choppy and laggy UX.
Number of page hold by a viewPager?
The number of items that any ViewPager will keep hold of is set by the setOffscreenPageLimit() method. The default value for the offscreen page limit is 3. This means ViewPager will track the currently visible page, one to the left, and one to the right. The number of tracked pages is always centered around the currently visible page.
Please follow this link for code: http://www.truiton.com/2013/05/android-fragmentpageradapter-example/
I know this post is old, but I struggled to figure this out so I'll answer it anyway.
You want to use FragmentStatePagerAdapter and override getItemPosition(). Create a list of stuff you want to pass down to the fragment, call notifyDataSetChanged(), and you're all set!
Here's the adapter:
public class SectionsPagerAdapter extends FragmentStatePagerAdapter {
List<String> mKeyList = new ArrayList<>();
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
#Override
public int getItemPosition(Object object) {
return POSITION_NONE;
}
#Override
public Fragment getItem(int position) {
// getItem is called to instantiate the fragment for the given page.
// Return a PlaceholderFragment (defined as a static inner class below).
return PlaceholderFragment.newInstance(mKeyList.get(position));
}
#Override
public int getCount() {
return mKeyList.size();
}
#Override
public CharSequence getPageTitle(int position) {
return "SCOUT " + (getCount() - position);
}
public void add(int position, String key) {
mKeyList.add(position, key);
notifyDataSetChanged();
}
}
And here's the fragment:
public static class PlaceholderFragment extends Fragment {
private static final String ARG_SCOUT_KEY = "scout_key";
public static PlaceholderFragment newInstance(String key) {
PlaceholderFragment fragment = new PlaceholderFragment();
Bundle args = new Bundle();
args.putString(ARG_SCOUT_KEY, key);
fragment.setArguments(args);
return fragment;
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.current_scout_fragment, container, false);
//getArguments().getString(ARG_SCOUT_KEY));
return rootView;
}
}
I want to dynamically add a new Fragment to the adapter when user swipes from right to left, and remove dynamically remove a Fragment when user swipes from left to right.
AFAIK, that will not be supported by any PagerAdadpter. It certainly will not be supported by ArrayPagerAdapter. The page needs to exist, otherwise you cannot swipe to it. You cannot swipe first, then add the page later.
Moreover, I have never found a use case for your proposed pattern that could not be handled by having the page be in the adapter, but not populating the page (i.e., whatever the expensive work is that you appear to be trying to avoid) until the swipe begins.
I am having a hard time figuring out the next thing.
What I have: I have a viewpager and several pages in it. In this question only two of them is important, lets call them Fragment1 and Fragment2 and they are next to each other. Fragment1 contains a listview which is filled with data from the internet (external database). Fragment2 contains a simple button.
My goal: If I click on the button in Fragment2, I add a new item to the external database. I would like to update/refresh the listview in the Fragment1 with this new item.
The notifyDataChanged() doesnt work in my case, however so far I was convinced that it reinstantiates every pages.. I am going to introduce my problem the clearest way I can, so lets see the code I have, this is my ViewPager adapter:
class MyPagerAdapter extends FragmentStatePagerAdapter {
public List<String> fragmentsA;
public MyPagerAdapter(FragmentManager fm) {
super(fm);
fragmentsA = fragments;
}
#Override
public Fragment getItem(int position) {
return Fragment.instantiate(context, fragmentsA.get(position));
}
#Override
public CharSequence getPageTitle(int position) {
return mEntries.get(position % CONTENT.length).toUpperCase();
}
#Override
public int getCount() {
return mEntries.size();
}
#Override
public int getItemPosition(Object object) {
return POSITION_NONE;
}
}
Fragment1 onCreateView() (shortly):
public View onCreateView(LayoutInflater inflater, final ViewGroup container,
Bundle savedInstanceState) {
getData();
View view = inflater.inflate(R.layout.latestapps_tab, container, false);
lw = (ListView) view.findViewById(R.id.lw);
context = getActivity().getApplicationContext();
act = this.getActivity();
m_adapter = new ItemAdapter();
lw.setAdapter(m_adapter);
return view;
}
I create the ViewPager and the adapter, I set the adapter for the ViewPager afterwards I fill the my viewpager with my fragments in my Main class. After this I am goint to have a fully functional ViewPager with 2 fragments.
pager = (ViewPager)findViewById( R.id.viewpager );
adapter = new MyPagerAdapter(getSupportFragmentManager());
indicator = (TabPageIndicator)findViewById( R.id.indicator );
pager.setAdapter( adapter );
indicator.setViewPager( pager );
pager.setCurrentItem(INITIAL_PAGE);
pager.setOffscreenPageLimit(3);
//adding fragments to the pager
fragments.add( Fragment1.class.getName());
fragments.add( Fragment2.class.getName());
In the Fragment1 I have a listview with some textviews in every list item. The loading works perfectly: I create the ArrayLists and I fill thoes lists with data from the external database. After loading is done, I fill the listviews with these tons of data.
In Fragment 2 I click on the button and I would like that listview to be updated so a new row should be created in the listview with some data from the external database. (of course writing into the database works)
My guess, that I might not refresh the ArrayLists or I dont reinstantiate the Fragment1, so the getDataFromSQL() method never turns only if I exit and launch the application again or I swipe so much in the ViewPager that the Fragment1 gets detached. So I cannot update or refresh the Fragment1. Could someone help in this questionL?
EDIT
I managed to make it happen with delivering a message to the fragment2 to update itself. But I am not sure if it is a good solution and there is not a better way, i.e. just refreshing somehow the whole fragment.
SOLUTION
Okay I think it must have been my laziness but I solved it now. For everyone who still wants to refresh a fragment from another one or just make conection between fragments, I tell you the appropriate approach:
You have to implement your own listener which helps you communicate between the fragments through the holder activity. This can be found here: http://developer.android.com/training/basics/fragments/communicating.html . Very simple and useful.
You have to retrieve the fragment, which is again simple: Retrieve a Fragment from a ViewPager These Q offers several acceptable way, I used the SpareArray solution.
Thank you for the help anyway!
you need be able to get your fragments from your activity, to do that you need to get the fragment from your adapter, you will need to add a couple methods to your page adapter
public Fragment getFragment(ViewPager container, int position, FragmentManager fm) {
String name = makeFragmentName(container.getId(), position);
return fm.findFragmentByTag(name);
}
private String makeFragmentName(int viewId, int index) {
return "android:switcher:" + viewId + ":" + index;
}
then from your activity make the following method
public Fragment getFragmentbyPosition(int position) {
return adapter.getFragment(pager, position, getSupportFragmentManager());
}
now on fragment2 call the following:
Fragment1 fragment1 = (Fragment1) ((MyActivity)getActivity()).getFragmentbyPosition(0);
now you will be able to call public methods on fragment1 from fragment 2, so just use that in your onClick and tell fragment1 to update it's listview.
now the reason makeFragmentName works is that is how the FragmentPagerAdapter creates the tag for the fragments it makes.