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Recyclerview has no LayoutManager android studio

I'm trying to implement RecyclerView in my android app but it gives me error
"RecyclerView has no Layoutmanager"
even though I initialize it in my code. My java and xml file:
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.activity_list, container, false);
mRecyclerView = rootView.findViewById(R.id.recyclerView);
RecyclerView.LayoutManager layoutManager = new LinearLayoutManager(getContext());
mRecyclerView.setLayoutManager(layoutManager);
mAdapter = new CustomAdapter(mDataset);
mRecyclerView.setAdapter(mAdapter);
return rootView;
}
XML
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".List"
android:background="#color/black">
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/recyclerView"
android:layout_width="match_parent"
android:layout_height="495dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="parent"/
</androidx.constraintlayout.widget.ConstraintLayout>

You can't use signal activity for recy.... And main activity . Plz create a new xml file like list_file

Are you sure that added recyclerview dependency into gradle
AndroidX
implementation 'androidx.recyclerview:recyclerview:1.1.0'
Support library
implementation 'com.android.support:recyclerview-v7:28.0.0'

Unable to update views through data binding on Android

I was trying to migrate from ButterKnife to Android data binding.
When using ButterKnife (which is working perfectly fine):
// Called after a network call
public void updateView(MyAdapter adapter, String title) {
toolbar.setTitle(title);
recyclerView.setHasFixedSize(true);
LinearLayoutManager layoutManager = new LinearLayoutManager(getContext());
recyclerView.setLayoutManager(layoutManager);
recyclerView.setAdapter(adapter);
}
Using Android data binding:
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
binding = MyFragmentBinding.inflate(inflater, container, false);
binding.toolbar.setTitle(R.string.app_name); // this works
return binding.getRoot();
}
// Called after a network call
public void updateView(MyAdapter adapter, String title) {
binding.toolbar.setTitle(title);
binding.recyclerView.setHasFixedSize(true);
LinearLayoutManager layoutManager = new LinearLayoutManager(getContext());
binding.recyclerView.setLayoutManager(layoutManager);
binding.recyclerView.setAdapter(adapter);
}
After calling updateView on the later code, the screen goes blank.
I debugged to find out that view remains attached to the Fragment.
Also, if I am updating something inside onCreateView then that works.
Is there anything am I doing wrong?
Layout:
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto">
<android.support.design.widget.CoordinatorLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:layout_alignParentTop="true"
android:background="?attr/colorPrimary"
android:elevation="#dimen/_6sdp"
android:theme="#style/ThemeOverlay.AppCompat.Dark.ActionBar"
app:navigationIcon="#drawable/default_nav_icon_back"
app:popupTheme="#style/ThemeOverlay.AppCompat.Light" />
<android.support.v7.widget.RecyclerView
android:id="#+id/recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginTop="?attr/actionBarSize" />
</android.support.design.widget.CoordinatorLayout>
</layout>

how to use Recycler View in custom dialog [duplicate]

This question already has answers here:
How can I display a list view in an Android Alert Dialog?
(12 answers)
Closed 6 years ago.
How can I display a list view in an Android Alert Dialog? i tried this.

Try this:
custom_dialog.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
<android.support.v7.widget.RecyclerView
android:id="#+id/my_recycler_view"
android:scrollbars="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
</LinearLayout>
Activity/Fragment.java
RecyclerView mRecyclerView;
AlertDialog.Builder builder = new AlertDialog.Builder(context);
LayoutInflater inflater = LayoutInflater.from(context);
View content = inflater.inflate(R.layout.custom_dialog, null);
builder.setView(content);
mRecyclerView = (RecyclerView) content.findViewById(R.id.my_recycler_view);

you should extend DialogFragment and create custom dialog which will have recycler view in it.
Layout :-fragment_dialog.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<android.support.v7.widget.RecyclerView
android:id="#+id/recycler_view"
android:scrollbars="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
</RelativeLayout>
your custom dialog :- MyDialogFragment
public class MyDialogFragment extends DialogFragment {
private RecyclerView mRecyclerView;
// this method create view for your Dialog
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
//inflate layout with recycler view
View v = inflater.inflate(R.layout.fragment_dialog, container, false);
mRecyclerView = (RecyclerView) v.findViewById(R.id.recycler_view);
//setadapter
//get your recycler view and populate it.
return v;
}
}

Fragments : unable to start activity Component Info

I'm really confused on what I've done with my code.
It's just a simple app using Fragments but I get below error :
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.sgrumo.sunshineonyourmind/com.example.sgrumo.sunshineonyourmind.MainActivity}: java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child's parent first.
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2646)
This is my MainActivity class :
public class MainActivity extends FragmentActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if(savedInstanceState==null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new MainActivityFragment()).commit();
}
}
Activity-main XML :
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout 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/container"
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"
tools:ignore="MergeRootFrame"
tools:context="com.example.sgrumo.sunshineonyourmind.MainActivity">
I just wanted a Fragment inside my activity main, what's wrong with my code?
This is the Fragment class i use :
public class MainActivityFragment extends Fragment {
public MainActivityFragment() {}
String[] forecastArray = {
"Today - Sunny - 31/20",
"Tomorrow - Sunny - 42,30",
"Wednesday - Rainy - 20,15",
"Thursday - FINIMONDO - 35,20"
};
ArrayList<String> list = new ArrayList<>(Arrays.asList(forecastArray));
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container);
ArrayAdapter<String> adapter = new ArrayAdapter<String>(getActivity(),R.layout.list_item_forecast,R.id.list_item_forecast_textview,list);
ListView lw = (ListView)rootView.findViewById(R.id.listview_forecast);
lw.setAdapter(adapter);
return rootView;
}
And its 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"
android:paddingBottom="#dimen/activity_vertical_margin"
android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
tools:context="com.example.sgrumo.sunshineonyourmind.MainActivityFragment"
tools:showIn="#layout/activity_main">
<ListView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="#+id/listview_forecast"
android:layout_gravity="center" />

Please change the code as following in your onCreateView method
View rootView = inflater.inflate(R.layout.fragment_main, container, false);
You missed to add false. Thanks.

Use getSupportFragmentManager().beginTransaction()
.replace(R.id.container, new MainActivityFragment()).commit() instead of getSupportFragmentManager().beginTransaction()
.add(R.id.container, new MainActivityFragment()).commit()

Binary XML file line #1: Error inflating class fragment

I'm trying to follow the Udacity Developing Android Apps course. I got to Lesson 3.03. Here, we are instructed to launch a new Activity (DetailActivity) from ForecastFragment when clicking an item in a list.
However, I keep getting an error when attempting to launch the DetailActivity. Binary XML file line #1: Error inflating class fragment, where it's caused by DetailActivity.java in it's onCreate() method.
I've already searched around, but none of the fixes suggested for this issue helped me at all.
The specific error is:
Caused by: android.app.Fragment$InstantiationException: Trying to instantiate a class
com.myapp.sunshine.app.DetailActivityFragment that is not a Fragment
DetailActivity.java
public class DetailActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_detail); //failing here
}
}
DetailActivityFragment.java
public class DetailActivityFragment extends Fragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment_detail, container, false);
}
}
activity_detail.xml
<fragment xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools" android:id="#+id/fragment"
android:name="com.myapp.sunshine.app.DetailActivityFragment"
tools:layout="#layout/fragment_detail" android:layout_width="match_parent"
android:layout_height="match_parent" />
I should mention that I'm not using support libraries--as I'm targeting SDK 21+, Lollipop only.
This isn't the only fragment we've created in the course either. The other fragment we created looks identical to this one.
activity_main.xml
<fragment xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools" android:id="#+id/fragment"
android:name="com.myapp.sunshine.app.ForecastFragment"
tools:layout="#layout/fragment_main" android:layout_width="match_parent"
android:layout_height="match_parent" />
And for good measure, I'm including the ForecastFragment class. I've omitted unnecessary parts of code.
ForecastFragment.java
public class ForecastFragment extends Fragment {
private ArrayAdapter<String> mForecaseAdapter;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setHasOptionsMenu(true);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
String[] forecastArray = {
"Today - Sunny - 88/63",
"Tomorrow - Foggy - 74/58",
"Sunday - Rainy - 65/59",
"Monday - Cloudy - 72/67"
};
final List<String> weekForecast = new ArrayList<>(Arrays.asList(forecastArray));
mForecaseAdapter = new ArrayAdapter<>(
getActivity(),
R.layout.list_item_forecast,
R.id.list_item_forecast_textview,
weekForecast);
View rootView = inflater.inflate(R.layout.fragment_main, container, false);
final ListView listView = (ListView) rootView.findViewById(R.id.listview_forecast);
listView.setAdapter(mForecaseAdapter);
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
String forecast = mForecaseAdapter.getItem(position);
Intent detailActivityIntent = new Intent(getActivity(), DetailActivity.class)
.putExtra(Intent.EXTRA_TEXT, forecast);
startActivity(detailActivityIntent);
}
});
return rootView;
}
}
fragment_detail.xml
<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:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
android:paddingBottom="#dimen/activity_vertical_margin" tools:context=".DetailActivityFragment">
<TextView android:text="#string/hello_world" android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</RelativeLayout>
which is nearly identical to
fragment_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" android:paddingLeft="#dimen/activity_horizontal_margin"
android:paddingRight="#dimen/activity_horizontal_margin"
android:paddingTop="#dimen/activity_vertical_margin"
android:paddingBottom="#dimen/activity_vertical_margin" tools:context=".MainActivityFragment">
<ListView
android:id="#+id/listview_forecast"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_gravity="center" />
</FrameLayout>

You should be using FragmentActivity instead of Activity
public class DetailActivity extends FragmentActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_detail); //failing here
}
}