Unable to attach Fragment to activity through XML

Question

I created a new activity by right clicking on my project and selecting new > fragment > blank fragment.

Here is the auto generated fragment. The only thing I added was the lines under the onCreateView() method. I also implemented onFragmentInteractionListener on the activity that I want to attatch this fragment to. I made sure to implement the onFragmentInteraction(...) method on that Activity, but left it blank.

Whats the problem here?

   import android.app.Activity;
import android.net.Uri;
import android.os.Bundle;
import android.text.Html;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import android.support.v4.app.Fragment;


public class FragmentHowToPlay extends Fragment {
    // TODO: Rename parameter arguments, choose names that match
    // the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
    private static final String ARG_PARAM1 = "param1";
    private static final String ARG_PARAM2 = "param2";

// TODO: Rename and change types of parameters
private String mParam1;
private String mParam2;

private OnFragmentInteractionListener mListener;

/**
 * Use this factory method to create a new instance of
 * this fragment using the provided parameters.
 *
 * @param param1 Parameter 1.
 * @param param2 Parameter 2.
 * @return A new instance of fragment FragmentHowToPlay.
 */
// TODO: Rename and change types and number of parameters
public static FragmentHowToPlay newInstance(String param1, String param2) {
    FragmentHowToPlay fragment = new FragmentHowToPlay();
    Bundle args = new Bundle();
    args.putString(ARG_PARAM1, param1);
    args.putString(ARG_PARAM2, param2);
    fragment.setArguments(args);
    return fragment;
}

public FragmentHowToPlay() {
    // Required empty public constructor
}

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    if (getArguments() != null) {
        mParam1 = getArguments().getString(ARG_PARAM1);
        mParam2 = getArguments().getString(ARG_PARAM2);
    }
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    View v = inflater.inflate(R.layout.fragment_fragment_how_to_play, container, false);

    TextView text1 = (TextView) v.findViewById(R.id.text1);

    text1.setText(Html.fromHtml(getString(R.string.my_text)));


    return v;


}

// TODO: Rename method, update argument and hook method into UI event
public void onButtonPressed(Uri uri) {
    if (mListener != null) {
        mListener.onFragmentInteraction(uri);
    }
}

@Override
public void onAttach(Activity activity) {
    super.onAttach(activity);
    try {
        mListener = (OnFragmentInteractionListener) activity;
    } catch (ClassCastException e) {
        throw new ClassCastException(activity.toString()
                + " must implement OnFragmentInteractionListener");
    }
}

@Override
public void onDetach() {
    super.onDetach();
    mListener = null;
}

/**
 * This interface must be implemented by activities that contain this
 * fragment to allow an interaction in this fragment to be communicated
 * to the activity and potentially other fragments contained in that
 * activity.
 * <p/>
 * See the Android Training lesson <a href=
 * "http://developer.android.com/training/basics/fragments/communicating.html"
 * >Communicating with Other Fragments</a> for more information.
 */
public interface OnFragmentInteractionListener {
    // TODO: Update argument type and name
    public void onFragmentInteraction(Uri uri);
}

}

Here is the logcat error:

    Process: mjj.fling, PID: 8965
java.lang.RuntimeException: Unable to start activity ComponentInfo{mjj.fling/mjj.fling.HowToPlayActivity}: android.view.InflateException: Binary XML file line #19: Error inflating class fragment
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2379)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2441)
        at android.app.ActivityThread.access$800(ActivityThread.java:162)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1349)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:135)
        at android.app.ActivityThread.main(ActivityThread.java:5431)
        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:913)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:706)
 Caused by: android.view.InflateException: Binary XML file line #19: Error inflating class fragment
        at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:763)
        at android.view.LayoutInflater.rInflate(LayoutInflater.java:806)
        at android.view.LayoutInflater.rInflate(LayoutInflater.java:809)
        at android.view.LayoutInflater.inflate(LayoutInflater.java:504)
        at android.view.LayoutInflater.inflate(LayoutInflater.java:414)
        at android.view.LayoutInflater.inflate(LayoutInflater.java:365)
        at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:402)
        at android.app.Activity.setContentView(Activity.java:2214)
        at mjj.fling.HowToPlayActivity.onCreate(HowToPlayActivity.java:16)
        at android.app.Activity.performCreate(Activity.java:6093)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)



 Caused by: android.app.Fragment$InstantiationException: Trying to instantiate a class mjj.fling.FragmentHowToPlay that is not a Fragment
        at android.app.Fragment.instantiate(Fragment.java:606)
        at android.app.Fragment.instantiate(Fragment.java:582)
        at android.app.FragmentManagerImpl.onCreateView(FragmentManager.java:2108)
        at android.app.Activity.onCreateView(Activity.java:5431)
        at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:733)



 Caused by: java.lang.ClassCastException

XML LAYOUT for Activity that Fragment is being attached to

<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="mjj.fling.HowToPlayActivity"
android:background="#01051D">

<ScrollView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/scrollView"
    android:layout_alignParentTop="true"
    android:layout_alignParentRight="true"
    android:layout_alignParentEnd="true"
    android:layout_marginTop="42dp" >

    <fragment
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:name="mjj.fling.FragmentHowToPlay"
        android:id="@+id/fragment"
        tools:layout="@layout/fragment_fragment_how_to_play" />
</ScrollView>

Answer 1

You fragment extends android.support.v4.app.Fragment instead of android.app.Fragment -- see the import declaration. The former is meant to be used by FragmentActivity (or better yet the new AppCompatActivity) from the support library, not with regular android.app.Activity. You need to change one or the other and in general be consistent about what you are using throughout the app.