Develop Reference

Android SDK error: Trying instantiate a class that is not a fragment

I am hardly trying to create a simple application with a top menu and a changeable view below (by pressing the buttons in the menu fragment we change the view of the fragment below).
So, I have 2 fragments inside the main view but when trying to run the application in the emulator I get an error like:
Cause by android.app (bla bla bla, piece of crap Eclipse doesn't even allow copying the errors):
Trying to instantiate a class com.example.android.topmenu that is not a fragment
So, these are my XML layouts:
main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<fragment
android:id="#+id/menuFragment"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:name="com.example.android.topmenu" >
</fragment>
<fragment
android:id="#+id/contentFragment"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:name="com.example.android.bottomcontent" >
</fragment>
</LinearLayout>
topmenu.xml
<?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" >
<Button
android:id="#+id/Button1"
android:layout_width="wrap_content"
android:layout_height="match_parent" />
</LinearLayout>
bottom_content.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:padding="10dp"
android:orientation="vertical">
<TextView
android:id="#+id/textView1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="#+string/content_text" />
</LinearLayout>
and these are the classes for the main activity and the fragments
main_activity
package com.example.android;
import com.example.android.R;
import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
public class OLife extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
// The activity is being created
super.onCreate(savedInstanceState);
// Set view
setContentView(R.layout.main);
}
#Override
protected void onDestroy() {
super.onDestroy();
// The activity is about to be destroyed.
super.onDestroy();
// Stop method tracing that the activity started during onCreate()
android.os.Debug.stopMethodTracing();
}
}
topmenu
package com.example.android;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
public class OLifeMenu extends Fragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.topmenu, container, false);
return view;
}
}
bottomcontent
package com.example.android;
import android.app.Activity;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
public class OLifeMain extends Fragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.bottom_content, container, false);
return view;
}
#Override
public void onAttach(Activity activity) {
super.onAttach(activity);
}
}

You should be using FragmentActivity instead of Activity that is because you are using support Fragments and multiple Fragments in your activity main
Edit
You can now use the Appcompat support library and extends AppCompatActivity to support toolbar and fragment for lower api.

In my case it turned out, I was doing stuff in onCreate in the wrong order:
setContentView(R.layout.activity_qr_code_scan);
super.onCreate(savedInstanceState);
instead of
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_qr_code_scan);

As you are using fragments in your layout and I suggest you to extend your class from fragment or fragment activity.

How to switch between fragments during onclick?

I have a project I'm trying to do. I ran into a little issue and I'm not sure how to get around it. Below is an image of the application so far.
What I would like it to do is when the user onclicks one of the list items, the part which says "Hello! It's Fragment2" changes to a new xml which I declared in the app. So if I click the ATO listItem, then the fragment on the right side should change to something like "Hello! It's ATO Fragment"
Here is my code so far:
AndroidListFragmentActivity:
package com.exercise.AndroidListFragment;
import android.app.Activity;
import android.os.Bundle;
public class AndroidListFragmentActivity extends Activity {
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
}
Fragment2:
package com.exercise.AndroidListFragment;
import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
public class Fragment2 extends Fragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
// TODO Auto-generated method stub
return inflater.inflate(R.layout.fragment2, container, false);
}
}
MyListFragment1:
package com.exercise.AndroidListFragment;
import android.app.ListFragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.Toast;
public class MyListFragment1 extends ListFragment {
String[] options ={
"ATO",
"BETA",
"DELT",
"PHI DELT",
"SAE",
"SIG NU",
"FIJI",
"SIG CHI",
"PHI PSI"
};
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
ListAdapter myListAdapter = new ArrayAdapter<String>(getActivity(), android.R.layout.simple_list_item_1, options);
setListAdapter(myListAdapter);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.listfragment1, container, false);
}
#Override
public void onListItemClick(ListView l, View v, int position, long id) {
// TODO Auto-generated method stub
Toast.makeText(getActivity(), getListView().getItemAtPosition(position).toString(), Toast.LENGTH_LONG).show();
}
}
Fragment2.xml
<?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="vertical" >
<TextView
android:id="#+id/fragment2text"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Hello! It's Fragment2" />
</LinearLayout>
listfragment1.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingLeft="8dp"
android:paddingRight="8dp">
<ListView android:id="#id/android:list"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_weight="1"
android:drawSelectorOnTop="false"/>
<TextView android:id="#id/android:empty"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:text="No data"/>
</LinearLayout>
main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="horizontal" >
<fragment
android:name="com.exercise.AndroidListFragment.MyListFragment1"
android:id="#+id/fragment1"
android:layout_weight="1"
android:layout_width="0px"
android:layout_height="match_parent" />
<fragment
android:name="com.exercise.AndroidListFragment.Fragment2"
android:id="#+id/fragment2"
android:layout_weight="2"
android:layout_width="0px"
android:layout_height="match_parent" />
</LinearLayout>

Not sure what's the minimal fix to get your code working, but have you looked at using a Navigation Drawer to switch between the fragments? It looks to me like the example in the official docs matches pretty much exactly what you want to achieve.
A key is to have some kind of container for the currently displayed fragment (instead of using <fragment> like in your XML). For example:
<FrameLayout
android:id="#+id/content_frame"
android:layout_width="match_parent"
android:layout_height="match_parent" />
Then, switching fragments goes something like this:
Fragment fragment = new Fragment2();
// Insert the fragment by replacing any existing fragment
FragmentManager fragmentManager = getFragmentManager();
fragmentManager.beginTransaction()
.replace(R.id.content_frame, fragment)
.commit();
Further reading: Add a Fragment to an Activity at Runtime in Android developer docs.

private void openFragment (int number) {
Fragment fragment = new Fragment();
switch (number) {
case FRAGMENT_1:
fragment = new *Fragment1*();
break;
case FRAGMENT_2:
fragment = new *Fragment2*();
break;
}
getSupportFragmentManager().beginTransaction()
.replace(R.id.fragment_frame, fragment)
.commit();
}

Fragment is not covering entire screen

please help
When I run my ListFragment actitivy and click on a fragment (either Buick or Mazda), the layout of the fragment I clicked on is supposed to replace and cover the entire screen but the
container containing the list of cars stays on the screen and my fragment layout is shown below it. How can I make my fragment's layout replace the entire screen?
I couldn't post my AVD image showing the screen because I don't have enough reputatons to do
but the screen was showing as below when I clicked on the first item on the list.
Buick
Mazda
Hello! It's a Buick
my Mainactivity
package in.cars.demo;
import android.app.Activity;
import android.os.Bundle;
public class CarsMainActivity extends Activity {
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
}
My ListFragment activity
package in.cars.demo;
import android.app.Fragment;
import android.app.FragmentTransaction;
import android.app.ListFragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.Toast;
public class CarsList extends ListFragment {
String[] cars = new String[] { "Buick", "Mazda" };
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
ListAdapter myListAdapter = new ArrayAdapter<String>(getActivity(), android.R.layout.simple_list_item_1, cars);
setListAdapter(myListAdapter);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.cars_container, container, false);
}
#Override
public void onListItemClick(ListView l, View v, int position, long id) {
Toast.makeText(getActivity(), getListView().getItemAtPosition(position).toString(), Toast.LENGTH_LONG).show();
switch (position) {
case 0:
Fragment fragment1 = new Fragment1();
FragmentTransaction transaction1 = getFragmentManager().beginTransaction();
transaction1.replace(R.id.car_fragment, fragment1);
transaction1.addToBackStack(null);
transaction1.commit();
break;
case 1:
Fragment fragment2 = new Fragment2();
FragmentTransaction transaction2 = getFragmentManager().beginTransaction();
transaction2.replace(R.id.car_fragment, fragment2);
transaction2.addToBackStack(null);
transaction2.commit();
break;
}
}
}
Fragment1
package in.cars.demo;
import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
public class Fragment1 extends Fragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment1, container, false);
}
}
Fragment2
package in.cars.demo;
import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
public class Fragment2 extends Fragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
return inflater.inflate(R.layout.fragment2, container, false);
}
}
main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<fragment
android:id="#+id/car_fragment"
android:name="in.cars.demo.CarsList"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
/>
</LinearLayout>
cars_container.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingLeft="4dp"
android:paddingRight="4dp">
<ListView android:id="#id/android:list"
android:layout_width="match_parent"
android:layout_height="0dip"
android:layout_weight="1"/>
</LinearLayout>
fragment1.xml
<?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="vertical" >
<TextView
android:id="#+id/frag1TV"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Hello! It's a Buick" />
</LinearLayout>
fragment2.xml
<?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="vertical" >
<TextView
android:id="#+id/frag2TV"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Hello! It's a Mazda" />
</LinearLayout>

The problem is that you set the layout_height of your fragment to wrap_content in your main.xml. The visible size will be reduced to the actual size of the fragment.
Change it to match_parent to fill the whole screen:
...
<fragment
android:id="#+id/car_fragment"
android:name="in.cars.demo.CarsList"
android:layout_width="match_parent"
android:layout_height="match_parent"
/>
...
Furthermore use match_parent instead of fill_parent in apps with API Level 8+. See this question for more information.
Edit:
You have to change the container for the Fragments. The Fragment set with the tag will be static. Every fragment will be set in addition to this container. To have a dynamic approach use a FrameLayout. Now you can replace the fragment which was in there before.
...
<FrameLayout
android:id="#+id/car_fragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
/>
...
To show your CarsList you have to do a Fragment transaction in your Activity.
getFragmentManager() / getSupportFragmentManager()
.beginTransaction()
.replace(R.id.car_fragment, new CarsList())
.addToBackstack(null)
.commit();

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#color/white"
android:clickable="true"
android:orientation="vertical">
Try to setUp a color background to your fragment. In this way the background covers the entire space.

It is a little bit late, but maybe I will help someone else. The problem is with 'fragment' in your activity xml layout file (main.xml). You have to change:
<fragment
android:id="#+id/car_fragment"
android:name="in.cars.demo.CarsList"
android:layout_width="fill_parent"
android:layout_height="wrap_content"/>
to
<fragment
android:id="#+id/car_fragment"
android:name="in.cars.demo.CarsList"
android:layout_width="match_parent"
android:layout_height="match_parent"/>

Android fragment not created after runtime

I'm trying to add a fragment to an activity after the content view in the activity has been set. I'm not using the compatibility package and have my target API set to 16. I'm expecting the activity to be set to the fragments layout after the setContentView method in the main activity but on runtime, the fragment is never added and the screen in blank. The callbacks for the life cycle events in the fragment are never called thus the System.outs don't output. Logcat doesn't output any errors relating to fragments either. If a fragment element is made in the activity_main.xml, the fragment works fine but adding it to the RelativeLayout in the class doesn't work. Can someone please help me? Thanks!
Edit: Tried using a FrameLayout as the fragment_container but no difference.
This is my main activity:
package com.example.derp;
import android.os.Bundle;
import android.app.Activity;
import android.app.Fragment;
import android.app.FragmentManager;
public class MainActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Fragment frag = new Fragment();
FragmentManager fManager = getFragmentManager();
fManager.beginTransaction().add(R.id.fragment_container, frag).commit();
}
}
This is my fragment:
package com.example.derp;
import android.app.Activity;
import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
public class Frag extends Fragment{
public Frag(){
}
#Override
public void onAttach(Activity activity) {
super.onAttach(activity);
System.out.println("onAttach");
}
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
System.out.println("onCreate");
}
#Override
public void onStart() {
super.onStart();
System.out.println("onStart");
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
System.out.println("onCreateView");
return inflater.inflate(R.layout.fragment_frag, container, false);//
}
}
This is the fragment_frag.xml:
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<Button
android:id="#+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:layout_centerVertical="true"
android:text="Button" />
<EditText
android:id="#+id/editText1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_above="#+id/button1"
android:layout_centerHorizontal="true"
android:layout_marginBottom="64dp"
android:ems="10"
android:inputType="textPersonName" >
<requestFocus />
</EditText>
</RelativeLayout>
The activity_main.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: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=".MainActivity" >
<RelativeLayout
android:id="#+id/fragment_container"
android:layout_width="match_parent"
android:layout_height="match_parent">
</RelativeLayout>
</RelativeLayout>

You are not creating the instance of your fragment class. Rather you are creating the base fragment class's object.
Change...
Fragment frag = new Fragment();
To...
Fragment frag = new Frag();

Difficulties with basic fragment layout

I'm trying to get my head around fragments in order to have my apps prepped for ICS.
I have the following files to just get the most basic fragment app you can have. It should have this when launched: One Fragment Layout with a text view "Fragment 1" and next to it another Fragment Layout with "Fragment2".
My package name is com.mwerner.fragments
My files are:
FragmentsActivity.java
ExamplesFragment.java
ExamplesFragment2.java
examples_fragment.xml
examples_fragment2.xml
main.xml
The code for FragmentsActivity.java is:
package com.mwerner.fragments;
import android.app.Activity;
import android.os.Bundle;
public class FragmentsActivity extends Activity {
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
}
ExamplesFragment.java
package com.mwerner.fragments;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
public class ExamplesFragment extends Fragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.examples_fragment, container, false);
}
}
ExamplesFragment2.java
package com.mwerner.fragments;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
public class ExamplesFragment2 extends Fragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.examples_fragment2, container, false);
}
}
The examples_fragment.xml files just have a linear layout with a textview in it...
Here is the code for the main.xml:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<fragment
class="com.mwerner.fragments$ExamplesFragment"
android:id="#+id/list"
android:layout_weight="1"
android:layout_width="0dp"
android:layout_height="fill_parent"
/>
<fragment
class="com.mwerner.fragments$ExamplesFragment2"
android:id="#+id/viewer"
android:layout_weight="2"
android:layout_width="0dp"
android:layout_height="fill_parent" />
</LinearLayout>
The app crashes on startup with the error
11-07 18:12:12.519: E/AndroidRuntime(696): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.mwerner.fragments/com.mwerner.fragments.FragmentsActivity}: android.view.InflateException: Binary XML file line #7: Error inflating class fragment
Can you please tell me what is wrong here? I pretty much copied / pasted the code from the google developers page for fragments.

You defined the path to your fragments incorrectly in your layout xml. Correct the class attributes. Try this:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<fragment
class="com.mwerner.fragments.ExamplesFragment"
android:id="#+id/list"
android:layout_weight="1"
android:layout_width="0dp"
android:layout_height="fill_parent"
/>
<fragment
class="com.mwerner.fragments.ExamplesFragment2"
android:id="#+id/viewer"
android:layout_weight="2"
android:layout_width="0dp"
android:layout_height="fill_parent" />
</LinearLayout>

Try extending FragmentActivity
public class FragmentsActivity extends FragmentActivity {
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
}

When I was writing my first program on Fragments using I incurred same error. Instead of extending "Activity" extend "FragmentActivity" in your launcher activity.