findViewById Attribute in Fragment from the activity xml Not work [duplicate] - android

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findViewById in Fragment
(37 answers)
Closed 2 years ago.
How to access an attribute in the activity xml?
I want to use it in fragment.
for example : this is my activity xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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"
xmlns:fab="http://schemas.android.com/apk/res-auto">
<androidx.constraintlayout.widget.ConstraintLayout
fab:layout_constraintTop_toTopOf="parent"
fab:layout_constraintLeft_toLeftOf="parent"
fab:layout_constraintRight_toRightOf="parent"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="#+id/layTitle"
android:layoutDirection="rtl"
android:background="#color/colorPrimary"
android:padding="#dimen/paddingTitle"
android:elevation="#dimen/elevationActivityTitle"
android:layout_alignParentTop="true">
<ImageView
fab:layout_constraintLeft_toLeftOf="parent"
fab:layout_constraintTop_toTopOf="parent"
fab:layout_constraintBottom_toBottomOf="parent"
android:layout_width="#dimen/imgActivityTitle"
android:layout_height="#dimen/imgActivityTitle"
android:id="#+id/btn_back"
android:src="#drawable/ic_back"
android:elevation="5dp"
android:layout_alignParentEnd="true"
android:layout_centerVertical="true"/>
</androidx.constraintlayout.widget.ConstraintLayout>
<FrameLayout
android:id="#+id/frag"
android:layout_width="0dp"
android:layout_height="0dp"
fab:layout_constraintBottom_toBottomOf="parent"
fab:layout_constraintTop_toBottomOf="#+id/layTitle"
fab:layout_constraintLeft_toLeftOf="parent"
fab:layout_constraintRight_toRightOf="parent"
/>
</androidx.constraintlayout.widget.ConstraintLayout>
I want findViewByid ImageView in fragment
When I was searching for solution I got the following one:
TextView btn_back= (TextView) getView().findViewById(R.id.btn_back)
But, unfortunately it was not working for me.

You can use the interface to do it :
Create an interface names IBtnClick with one void method: "void onBtnClicked();"
use interface in activity like this:
IBtnClick iBtnClick= (IBtnClick)getActivity();
here getAtivity is our context, if it doesn't work use another scope context.
and use your method in button click listener like this
iBtnClick.onBtnClicked();
Now in your fragment you have to implements interface and
you can add any action you want in Overrided method.

Use either viewModel or interfaces to talk between activity and fragment. don't try to send the button to fragment but trigger it from there. That will prevent any leaks or null pointers.

Ok. You have some options.
Firstly, you can access these variables to directly in fragment like that.
MainActivity.java
TextView backButton;
backButton = findViewById(R.id.btn_back);
Fragment.java
((MainActivity) getActivity()).backButton
You can get current activity with getActivity() but Java compiler cannot understand which activity so have to cast to MainActivity.
Secondly, you can pass your activity instance to fragment. You can use constructors and newInstance() function. You can read that post Best practice for instantiating a new Android Fragment
In my opinion, I prefer second option because you guarantee these variables that include activity class. Some devices occur errors at first option. But second option uses more ram because you are passing your variables to another class.
The choice is yours

Try This code
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
view = inflater.inflate(R.layout.recharge_plane_fragment, container, false);
alertdialog_Listview=view.findViewById(R.id.alertdialog_Listview);
return view;
}

You can declare your TextView btn_back as static in activity
public static TextView btn_back;
btn_back = (TextView) findViewById(R.id.btn_back);
and get it in fragment
TextView btn_back = ((MainActivity)getActivity()).btn_back;

Related

Pass data to multiple fragments

I am building a view with 2 fragments inside it. Inflating the layout works fine. But I got another problem. Before creating these fragments I need to pass some data to those fragments (FragmentListSchema and FragmentSchemaDetail).I thought of application variables but I guess that's not the proper way. How can I do it ?
Thanks in advance
Inflate :
public class FragmentSchemaTotal extends Fragment{
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// TODO Auto-generated method stub
View view = inflater.inflate(R.layout.fragment_schema,container);
return view;
}
}
Layout :
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal">
<fragment android:name="kine.gui.FragmentListSchema"
android:id="#+id/list"
android:layout_weight="1"
android:layout_width="0dp"
android:layout_height="match_parent" />
<fragment android:name="kine.gui.FragmentSchemaDetail"
android:id="#+id/viewer"
android:layout_weight="2"
android:layout_width="0dp"
android:layout_height="match_parent" />
</LinearLayout>
Use Fragment setArguments to pass data
FragmentSchemaTotal fragment = new FragmentSchemaTotal();
Bundle bundle = new Bundle();
bundle.putString("data","your data");
fragment.setArguments(bundle);
Why not use loaders inside of the fragments to have them load the data themselves? The usefulness of the Loader kind of depends on what type of data you are dealing with, though. It's tough to suggest the proper way without knowing more.
If Loaders don't fit the bill, you could have the activity find the fragment and set the data on them. Until that happens, the fragment could display a spinner instead of it's view. Once the data is set, the fragment can then display it's views.
The last alternative is to create the fragments in code and pass arguments to them. This isn't quite as flexible though. I would recommend the loader.

Using FragmentActivity throws InflateException

Common Fragment to be used in 2 Activity's
public class Ads extends Fragment {
private View rootView ;
private MoPubView adView ;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
rootView = inflater.inflate(R.layout.ads, container, true) ;
adView = (MoPubView) rootView.findViewById(R.id.adView) ;
adView.setAdUnitId(LogoQuizUtil.MOPUB_AD_UNIT);
adView.loadAd();
return rootView;
}
}
Fragment layout
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/ad_layout"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:gravity="bottom" >
<com.mopub.mobileads.MoPubView
android:id="#+id/adView"
android:layout_width="fill_parent"
android:layout_height="50dp"
android:layout_marginTop="10dp"
android:gravity="bottom" />
</LinearLayout>
Other Layout where I include this fragment
<fragment
android:id="#+id/ads"
android:name="myPackage.Ads"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:gravity="bottom" />
I get a dont get a exception when I call setContentView (R.layout.ads) the first time, when the second activity calls the fragementactivity (Ads) I get a exception at setContentView (R.id.ads).
Exception I get is
08-07 09:38:30.359: W/System.err(975): java.lang.RuntimeException: Unable to start activity ComponentInfo{mypackage/mypackage.SecondActivity}: android.view.InflateException: Binary XML file line #263: Error inflating class fragment
Lets start at the beginning. An activity is not a fragment and a fragment is not an activity.
You need an activity to contain/control fragments. To do that you extend Activity (for Honeycomb+ development) or use the support library and extend FragmentActivity. In this class you would use setContentView to set the layout that will contain the fragment(s).
You then, from that class, call the fragment manager (getFragmentManager or getSupportFragmentManager depending on which class you have extended). The fragment manager is then used to create, attach and detach the fragments.
The fragment, not being an activity, is coded differently. It should have an onCreateView method that inflates the layout for the fragment and returns it to the fragment manager from the activity.
Then it is typical to use onActivityCreated for the rest of your code (or whatever else is needed).
Making the changes to use fragments properly may or may not solve all of your problems, as I see you are using some kind of custom widget in your layout and the issue could be there too.

Android findViewById returning null

I'm using a button to call a method that just places input text into a textview. Whenever I use findViewById, it returns null.
public void encode(View view){
TextView out = (TextView) view.findViewById(R.id.encoderout);
EditText in = (EditText) view.findViewById(R.id.encoderin);
out.setText(in.getText().toString());
out.setTypeface(font);
}
My xml is here
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/input"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
>
<EditText android:id="#+id/encoderin"
android:layout_width="0dp"
android:layout_weight="2"
android:layout_height="wrap_content"
android:hint="Text to encode"/>
<Button android:id="#+id/encoderbutton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="encode"
android:text="Encode!"/>
</LinearLayout>
<TextView android:id="#+id/encoderout"
android:text="test"
android:layout_width="fill_parent"
android:layout_weight="1"
android:gravity="center"
android:layout_height="wrap_content"/>
</LinearLayout>
Almost every post I could find said that cleaning the project helped solve the problem but not in this case.
EDIT: ADDITIONAL INFO
I'm using Fragments, and this is my fragment code
public static class Encoder extends Fragment{
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.encoder, container, false);
return view;
}
}
It's calling up into the Activity because of the way buttons work. I can call the find methods fine in the fragment, but not when I have to go back to the activity.
I can verify the view is not null, it prints out fine when the toString is called in the method.
Solution: Never realized that I had to use the main view, thought I was SUPPOSE to use the button view. I'm very new to this (started today) thankyou everyone for the input!
<Button android:id="#+id/encoderbutton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="encode"
android:text="Encode!"/>
The parameter view in callback method encode(View view) in the Java code is supplied with the Button view itself but not the Activity.
See Reference below:
http://developer.android.com/reference/android/widget/Button.html
Fragments don't receive onClicks methods that are declared in the XML. You need to define encode in your Activity instead, then direct the desired behavior to the appropriate Fragment. Annoying, but that's the way it's done. I suggest you just implement the OnClickListener programatically in your Fragment code to avoid intertwining the behavior of your fragment and activity.

Two fragments hold by another fragment - findViewById returns null

I need help for my first Android application. I have a single activity with an Action Bar at the top and Navigation Tabs. Because of these navigation tabs I had to convert my Activities into Fragments.
So one of those Activities (which is now a Fragment) held two fragments, one ListFragment on the Left and a DetailFragment on the right, so that the user is able to select an item from the list and directly sees details on the right.
But now as the Activity has been transformed into the Fragment, it's the Fragment that holds the List- and the DetailFragment. This works fine until I want to change the DetailsFragment.
First of all, here is the code of the Fragment holding the other two:
public class BlackboardFragment extends Fragment {
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
return inflater.inflate(R.layout.fragment_layout, container, false);
}
}
Here is the fragment_layout.xml file (saved in layout-land):
<?xml version="1.0" encoding="UTF-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal" >
<fragment
android:id="#+id/interfaces"
android:layout_width="0px"
android:layout_height="match_parent"
android:layout_marginRight="20dp"
android:layout_weight="0.60"
class="org.fawkesrobotics.app.InterfaceFragment" />
<FrameLayout
android:id="#+id/viewer"
android:layout_width="0px"
android:layout_height="match_parent"
android:layout_weight="1" />
</LinearLayout>
So, the ListFragment is named InterfaceFragment, here is the code:
public class InterfaceFragment extends ListFragment {
boolean mDualPane;
// some other code
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setHasOptionsMenu(true);
create_list();
View viewerFrame = getActivity().findViewById(R.id.viewer);
mDualPane = viewerFrame != null
&& viewerFrame.getVisibility() == View.VISIBLE;
if (savedInstanceState != null) {
mCurCheckPosition = savedInstanceState.getInt("curChoice", 0);
}
}
// some other code
}
This is, where it doesn't work. The Fragment actually shows the list (that is created in create_list() where the ListAdapter and everything else is set), but my problem is, that viewerFrame is null. I declared the id viewer in the xml file above, so I don't understand why he cannot find the id. Does it "belong" to the BlackBoardFragment or to my overall activity? Because in BlackboardFragment I also tried it with getActivity().findViewById and it worked. Why is InterfaceFragment not able to find it?
I also tested, if he really uses the fragment_layout.xml in layout-land and he does. So he should know the id viewer, but obviously doesn't.
If you need more code or the code from the DetailsFragment, I can post it.
Thank you in advance for your help! :)
use FragmentManager to get Fragment......
ExampleFragment fragment = (ExampleFragment) getActivity().getFragmentManager().findFragmentById(R.id.example_fragment);
Nested Fragments are not supported by the Android SDK. That is, you can't have a "fragment within a fragment" in your Android application. Sorry.
EDIT:
Nested Fragments are now part of the official Android 4.2 SDK! Yay!

Do not get the rootLayoutContainer in a Fragment (Android 3.0 Preview)

I'm currently getting into the fragment API of the Android 3.0 Preview and have built the following minimal coding:
I have an Activty, which shall embed Fragment(s), which is currently implemented like this:
public class Cockpit extends Activity {
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.cockpit);
}
public static class InfoFragment extends Fragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
ViewGroup infoFragmentRoot = (ViewGroup) getActivity().findViewById(
R.id.infoFragmentRoot) ;
return inflater.inflate(R.id.infoFragment, container, false);
}
}
}
The corresponding layout of the activity:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<fragment android:name="test.android.ui.cockpit.Cockpit$InfoFragment"
android:id="#+id/infoFragment"
android:layout_weight="1"
android:layout_width="10dp"
android:layout_height="match_parent" >
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent"
android:layout_height="match_parent" android:padding="12dp" android:id="#+id/infoFragmentRoot" >
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="#string/hello"
/>
</LinearLayout>
</fragment>
Now, I do not understand why the ViewGroup container in the onCreateView() in the internal class InfoFragment is a nullpointer, nor do I understand,
why
ViewGroup infoFragmentRoot = (ViewGroup) getActivity().findViewById(
R.id.infoFragmentRoot) ;
returns also null.
Thanks for feedback.
You've got a few problems here. First of all, you don't want to be adding tags inside of the <fragment> tag. Think of the fragment tag as a placeholder. The fragment's onCreateView() method is responsible for defining the view hierarchy of your fragment, not the activity's layout XML file. What you can do though is create a separate layout XML file to be just the fragment's layout. Then inside of onCreateView(), you take the inflater passed in, and do something like this:
View v = inflater.inflate(R.layout.frag1, container, false);
TextView text1 = (TextView) v.findViewById(R.id.text1);
text1.setText( myTextData );
return v;
Notice that the attach parameter to inflate() is false? Android will take care of attaching the returned view to your container later.
Your activity's view hierarchy is not guaranteed to be in existence until the fragment gets the onActivityCreated() callback. So the attempt to get infoFragmentRoot could return null inside of onCreateView(). But I'm not even sure what is going on when that tag is buried inside of your <fragment>.
In this particular case, where you've embedded the tag in your activity's layout, the onInflate() callback of your fragment will be called with the rest of the attributes from your tag. The theory is that you could add those attributes to the arguments bundle on your fragment, then retrieve those values later in onCreateView() (using setArguments() and getArguments()). I say in theory because it appears there's a bug in the code that handles a configuration change (e.g., landscape to portrait), resulting in onInflate() being called after onCreateView() when the fragment is being reconstructed after a configuration change. See defect report http://code.google.com/p/android/issues/detail?id=14796.
For now, I recommend you extract your fragment's layout to a separate layout XML file (e.g., frag1.xml), the use my code above to inflate that layout in onCreateView(). And don't worry about any attributes being passed to onInflate().
You also do not want to use onCreate to instantiate your layout, that all will be handled within the parent activity. Saving the bundle is about all ive done there so far

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