How do I find the fragment that includes a particular view?
It is easy to find a view knowing the fragment and the view id:
fragment.getView().findViewById(R.id.foo)
But what I want to do is the reversal: knowing the view, find the fragment.
So far the best idea is:
I. Set the root view's tag to the fragment that inflated it:
// in a class that extends Fragment:
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_id, container, false);
rootView.setTag(this); // <======= !!!
return rootView;
}
II. Then, it's relatively easy to find that root view among view's parents:
// in some utility class:
public static Fragment getTagFragment(View view) {
for (View v = view; v != null; v = (v.getParent() instanceof View) ? (View)v.getParent() : null) {
Object tag = v.getTag();
if (tag != null && tag instanceof Fragment) {
return (Fragment)tag;
}
}
return null;
}
III. Usage:
Fragment f = getTagFragment(view);
PS I can even place an onClick handler into a Fragment, and it works!
Related
What I need to achieve
A screen displaying a ListView, which can be replaced by an error screen in case of problems (missing connection, server unavailable and the like).
I need to be able to switch (programmatically) back and forth between these two screens.
Requirements
The main screen must be a Fragment.
This is because my application is composed of several sections, each one accessible from the navigation drawer.
What I have done so far
The main fragment class is named AllQueuesFragment: its XML layout consists of a FrameLayout, which I use in combination with the FragmentManager to switch between ErrorFragment (containing the error message) and QueuesViewFragment (containing the ListView).
public class AllQueuesFragment extends Fragment
{
public AllQueuesFragment()
{
super();
}
#Override
public void onStart()
{
super.onStart();
// Show the right fragment based on connectivity status
checkConnection();
}
public void checkConnection()
{
final NetworkManager netManager = NetworkManager.getInstance(this.getActivity());
if (netManager.isConnected())
showQueues();
else
showNoConnection();
}
public void showNoConnection()
{
ErrorFragment fragNoConnection = new ErrorFragment();
displayFragment(fragNoConnection);
fragNoConnection.setTitle(R.string.text_no_connection);
fragNoConnection.setIcon(R.drawable.thatfeel);
fragNoConnection.setLoaderVisibility(false);
}
public void showQueues()
{
QueuesViewFragment fragQueuesView = new QueuesViewFragment();
displayFragment(fragQueuesView);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
// Inflate the view
View rootView = inflater.inflate(R.layout.fragment_allqueues, container, false);
return rootView;
}
// Displays a new fragment
public void displayFragment(Fragment fragment)
{
if (fragment != null)
{
FragmentManager fragmentManager = getFragmentManager();
fragmentManager.beginTransaction().replace(R.id.frame_container, fragment).commit();
}
}
}
The error screen is the following:
public class ErrorFragment extends Fragment
{
private TextView textTitle;
public ErrorFragment()
{
super();
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
// Inflate the view
View rootView = inflater.inflate(R.layout.fragment_error, container, false);
// Get the widgets
textTitle = (TextView)rootView.findViewById( R.id.fragment_error_text );
return rootView;
}
// Set methods
public void setTitle(int id) { textTitle.setText(id); }
}
The problem
The setTitle() method gets called before the layout is ready, and as a result, a NullPointerException is thrown.
class AllQueuesFragment
{
....
public void displayFragment(Fragment fragment)
{
if (fragment != null)
{
FragmentManager fragmentManager = getFragmentManager();
fragmentManager.beginTransaction().replace(R.id.frame_container, fragment).commit();
}
}
public void showNoConnection()
{
ErrorFragment fragNoConnection = new ErrorFragment();
displayFragment(fragNoConnection);
// PROBLEM HERE: Before calling setTitle(), I must be sure that ErrorFragment's
// layout is inflated!
fragNoConnection.setTitle(R.string.text_no_connection);
}
....
}
class ErrorFragment
{
....
public void setTitle(String value) { textTitle.setText(value); }
....
}
I can't call setTitle() directly from ErrorFragment::onCreateView(), because I don't know beforehand which message I need to show.
How can I ensure that fragNoConnection has completed its layouting?
Is there a better way to achieve my goal?
Unsatisfying workaround
The only workaround I can think of is to use a buffer to defer the actual call:
class ErrorFragment
{
// This string will hold the title until the layout is inflated
private String titleBuffer;
private TextView textTitle = null;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
// Inflate the view
View rootView = inflater.inflate(R.layout.fragment_error, container, false);
// Get the widgets
textTitle = (TextView)rootView.findViewById( R.id.fragment_error_text );
// Do the actual set
setTitle(titleBuffer);
return rootView;
}
....
public void setTitle(String value)
{
titleBuffer = value;
// If the layout is not inflated, defer the actual set
if (textTitle != null)
textTitle.setText(titleBuffer);
}
....
}
but I don't like this solution very much (the code above is simplified; ErrorFragment has more properties).
Advices?
Thanks in advance
This is exactly the type of thing arguments are supposed to be used for:
public void showNoConnection() {
ErrorFragment fragNoConnection = new ErrorFragment();
Bundle args = new Bundle();
//you can also use putInt here if you'd rather pass a string resource id, along with anything else you can stick into a Bundle
args.putString("title", "some title");
fragNoConnection.setArguments(args);
displayFragment(fragNoConnection);
}
Then in ErrorFragment
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_error, container, false);
TextView textTitle = (TextView)rootView.findViewById( R.id.fragment_error_text );
//now retrieve the argument...
textTitle.setText(getArguments().getString("title"));
return rootView;
}
The Fragment will even remember it's arguments after an orientation change.
If you feel like being pedantic, you can create a static factory method within ErrorFragment that takes the title as an argument and then creates the Fragment and adds the argument, that way you can achieve proper encapsulation :)
You need to have a callback method in your ErrorFragment and when the view is inflated you then call the method in your callback interface in the onViewCreated and set the title.
sample:
in ErroFragment
public class ErroFragment extends Fragment
{
static interface ErrorDone{
public void doneInflating();
}
private TextView textTitle;
private ErrorDone ed;
public ErroFragment()
{
super();
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
// Inflate the view
View rootView = inflater.inflate(R.layout.fragment_error, container, false);
// Get the widgets
textTitle = (TextView)rootView.findViewById( R.id.fragment_error_text );
return rootView;
}
// Set methods
public void setTitle(int id) { textTitle.setText(id); }
public void setInterFace(ErrorDone er){ this.ed = er; }
}
Then you implement the interface in your AllQueuesFragment
public class AllQueuesFragment extends Fragment implements ErroFragment.ErrorDone
It will generate method doneInflating
and you need to set the interface:
public void showNoConnection()
{
ErrorFragment fragNoConnection = new ErrorFragment();
displayFragment(fragNoConnection);
fragNoConnection.setInterFace(this);
}
And in the generated method(doneInflating) of the AllQueuesFragment you then set the title in there:
public void doneInflating(){
fragNoConnection.setTitle(R.string.text_no_connection);
fragNoConnection.setIcon(R.drawable.thatfeel);
fragNoConnection.setLoaderVisibility(false);
}
If you want to be sure that the FragmentTransaction is commited and effective, you can use the executePendingTransactions method:
FragmentManager fragmentManager = getFragmentManager();
fragmentManager.beginTransaction().replace(R.id.frame_container, fragment).commit();
fragmentManager.executePendingTransactions();
But, the right way to do it is to send the title value to the Fragment when instantiating it. This is the default pattern when you create a Fragment from your IDE (eclipse or Android Studio)
In Xamarin, I have a ViewPager that is performing the following error:
java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child's parent first.
This error occurs when I have three Android.Support.V4.App.Fragments and I swipe between them. This error does not happen with two Android.Support.V4.App.Fragments.
Here is my Android.Support.V4.App.Fragment code:
public class FragmentItem : Android.Support.V4.App.Fragment
{
View rootView;
TextView textView;
public override View OnCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
if (rootView == null)
{
rootView = inflater.Inflate(Resource.Layout.FragmentItem, container,false);
textView = rootView.FindViewById<TextView>(Resource.Id.textViewDisplay);
}
return rootView;
}
}
Here is my ViewPagerAdapter code:
public class ViewPagerAdapter : FragmentPagerAdapter {
private List<Android.Support.V4.App.Fragment> fragments;
int fragmentCount;
public ViewPagerAdapter(Android.Support.V4.App.FragmentManager fm, List<Android.Support.V4.App.Fragment> fragments) : base(fm)
{
this.fragments = fragments;
fragmentCount = fragments.Count;
}
public override int Count
{
get
{
return fragmentCount;
}
}
public override Android.Support.V4.App.Fragment GetItem (int position)
{
return fragments[position];
}
}
Why is this error happening and how can I prevent this error from happening?
Thanks in advance
EDIT
Here is the code that I have tried:
if (rootView != null)
{
ViewGroup parent = (ViewGroup)View.Parent;
parent.RemoveView(rootView);
} else {
rootView = inflater.Inflate(Resource.Layout.FragmentItem, container, false);
textView = rootView.FindViewById<TextView>(Resource.Id.textViewDisplay);
}
return rootView;
Here is the error that I am getting:
System.NullReferenceException: Object reference not set to an instance
of an object
At this line of code:
ViewGroup parent = (ViewGroup)View.Parent;
Use this in your onCreateView() method,
if (rootView != null) {
ViewGroup parent = (ViewGroup) rootView.getParent();//Updated
parent.removeView(rootView);
} else {
rootView = inflater.inflate(Resource.Layout.FragmentItem, container,
false);
}
this will remove the view from its parent view if this already has parent view.
I'm making a downloader app, and i got child's parents error after the onCreateView return section.
I tried a lots of things, but nothing help. I tried:
((ViewGroup)dlistView.getParent()).removeView(dlistView);
after that the compiler says:
01-12 12:05:15.558: E/AndroidRuntime(10740): java.lang.RuntimeException: Your content must have a ListView whose id attribute is 'android.R.id.list'
or remove the container/ i got an npe/ or remove the V but the V.getParent() is null.
Which view is the parent, and which is the child?
The code:
public static class DownloadingFragment extends ListFragment {
public static final String ARG_SECTION_NUMBER = "section_number";
public DownloadingFragment() {
}
#Override
public View onCreateView (LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View V = inflater.inflate (R.layout.list, null);
ListView dlistView = (ListView) V.findViewById(R.id.dlist);
List<DownloadInfo> downloadInfo = new ArrayList<DownloadInfo>();
downloadInfo.add(new DownloadInfo("File", 1000));
DownloadInfoArrayAdapter diaa = new DownloadInfoArrayAdapter(
getActivity().getApplication(),R.layout.list, downloadInfo);
dlistView.setAdapter(diaa);
return dlistView; // throw exception
}
}
//...
}
Thank you in advance for your help.
EDIT:
the new code:
public static class DownloadingFragment extends Fragment {
public static final String ARG_SECTION_NUMBER = "section_number";
public DownloadingFragment() {
}
#Override
public View onCreateView (LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View V = inflater.inflate (R.layout.list, null);
return V;
}
#Override
public void onStart() {
// TODO Auto-generated method stub
super.onStart();
ListView dlistView = (ListView) getView().findViewById(R.id.dlist);
List<DownloadInfo> downloadInfo = new ArrayList<DownloadInfo>();
downloadInfo.add(new DownloadInfo("File", 1000));
DownloadInfoArrayAdapter diaa = new DownloadInfoArrayAdapter(
getActivity().getApplication(),R.layout.list, downloadInfo);
dlistView.setAdapter(diaa);
}
}
//...
}
that's because you return the listview which has a parent (somewhere in V's layout tree) .
for any type of fragment , onCreateView should return a view that doesn't have any parent .
in this case , since it's a listFragment , create the listview (either using xml or programmatically ) , and then return it . do not allow it to have any parents since it needs to have a parent as a fragment .
read here for more information :
The system calls this when it's time for the fragment to draw its
user interface for the first time. To draw a UI for your fragment, you
must return a View from this method that is the root of your
fragment's layout. You can return null if the fragment does not
provide a UI.
Note that the third argument of inflate is false.
so replace this line
View V = inflater.inflate (R.layout.list, null);
with this
View V = inflater.inflate (R.layout.list, null,false);
and you are done.hope this helps.
I am trying to implement Fragments in my Project using the https://github.com/JakeWharton/Android-ViewPagerIndicator plugin.
My Fragment
public final class NearByFragment extends Fragment {
private static String TAG = "bMobile";
public static NearByFragment newInstance(String content) {
NearByFragment fragment = new NearByFragment();
return fragment;
}
#Override
public void onCreate(Bundle savedInstanceState) {
Log.d(TAG, "onCreate");
super.onCreate(savedInstanceState);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
Log.d(TAG, "onCreateView");
return inflater.inflate(R.layout.fragment_search_nearby, null);
}
}
Now I want to execute some code like start start a new thread and download a JSON from the server and then assign a list view from the content I download. In fragments we are assigning views in onCreateView. so where should I write the
listview = (ListView) findViewById(R.id.list_items);
((TextView) findViewById(R.id.title_text))
.setText(R.string.description_blocked);
and other code to generate the Fragment view ?
You can search within the view that you just inflated:
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
Log.d(TAG, "onCreateView");
View v = inflater.inflate(R.layout.fragment_search_nearby, null);
listview = (ListView)v.findViewById(R.id.list_items);
((TextView)v.findViewById(R.id.title_text))
.setText(R.string.description_blocked);
return v;
}
You can also use the Fragment.getView() function elsewhere in your code and call that view's findViewById() member.
You can use getActivity().findByView() from the Fragment if you want to have access to the layout elements. Alternatively, you can just put the findByView() call in the main Activity.
I'm working on 3.0 for the first time.
I want to add fragments dynamically , but its shown error:-
10-18 18:29:11.215: ERROR/AndroidRuntime(3550): java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child's parent first.
XML code
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/frags">
<ListView
android:id="#+id/number_list"
android:layout_width="250dip"
android:layout_height="match_parent" />
<FrameLayout
android:id="#+id/the_frag"
android:layout_width="match_parent"
android:layout_height="match_parent" />
Activity
public class FragmentExampleActivity extends Activity implements
OnItemClickListener {
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
ListView l = (ListView) findViewById(R.id.number_list);
ArrayAdapter<String> numbers = new ArrayAdapter<String>(
getApplicationContext(), android.R.layout.simple_list_item_1,
new String[] { "one", "two", "three", "four", "five", "six" });
l.setAdapter(numbers);
l.setOnItemClickListener(this);
}
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Fragment f = new FragmentExample();
FragmentTransaction ft = getFragmentManager().beginTransaction();
ft.replace(R.id.the_frag, f);
ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
ft.addToBackStack(null);
ft.commit();
}
}
public class FragmentExample extends Fragment {
private int nAndroids=1;
public FragmentExample() {
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle saved) {
int n;
View l = inflater.inflate(R.layout.textlay,container);
TextView tv = (TextView) l.findViewById(R.id.textView1);
tv.setText("value "+nAndroids);
return l;
}
}
Plz put some light on , where i'm going wrong :(
Instead of using
View l = inflater.inflate(R.layout.textlay,container);
you should use
View l = inflater.inflate(R.layout.textlay, container, false);
or alternatively
View l = inflater.inflate(R.layout.textlay, null );
I strongly suggest you to use, the version of inflate which takes three parameters. Android use the container only for the layout's params purpose. Passing false as third parameter, prevents the addition of textlay, to container and fixes your issue
if in onCreateView() , you want to reuse view , then you can deal with onDestroyView()
#Override
public void onDestroyView() {
super.onDestroyView();
if (view != null) {
ViewGroup parentViewGroup = (ViewGroup) view.getParent();
if (parentViewGroup != null) {
parentViewGroup.removeAllViews();
}
}
}
or you can use third argument and pass it as a false.
inflater.inflate(R.layout.sample_fragment, container,false);
it means that don't attach current view to root.
The following solves multiple problems:
public static View contentView;
public static class MenuCardFrontFragment extends Fragment {
public MenuCardFrontFragment() {
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
try
{
LinearLayout frontLayout = (LinearLayout)inflater.inflate(R.layout.content_card, container, false);
// modify layout if necessary
return contentView = frontLayout;
} catch (InflateException e) {
return contentView;
}
}
#Override
public void onDestroyView() {
super.onDestroyView();
if (contentView != null) {
ViewGroup parentViewGroup = (ViewGroup) contentView.getParent();
if (parentViewGroup != null) {
parentViewGroup.removeAllViews();
}
}
}
}
If fragments shows with animation and user forced to repeat the animation before it's over. ex: pressing menu button twice before the menu fragment finishes animating and appear. (this got solved by the onDestryView from user2764384)
If inflate method called with specifying the container to get container lay outing. it looks like that cases a problem because at the 2nd time that happened the old container already have a view. so if that exception happen it will be caught and returns the old view contentView.