Android app crashing (fragment and xml onclick)

Question

second_fragment.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/f2_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >

<TextView
    android:id="@+id/f2_textview"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="@string/f2_tv" />

<Button
    android:id="@+id/f2_button"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:onClick="button"
    android:text="@string/f2_bttn" />

SecondFragment.java

   public class SecondFragment extends Fragment {

    FragmentInterface iface;

    public interface FragmentInterface {
        public void buttonPressed();
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {

        return inflater.inflate(R.layout.second_fragment, container, false);
    }

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);

        // This makes sure that the container activity has implemented
        // the callback interface. If not, it throws an exception
        try {
            iface = (FragmentInterface) activity;
        } catch (ClassCastException e) {
            throw new ClassCastException(activity.toString()
                    + " must implement FragmentInterface");
        }

    }

    public void button(View view) {

    }
}

I'm newbie and I have no idea why my application crash, when button is pressed ? Can anyone explain?

01-03 13:28:25.612: E/AndroidRuntime(1276): FATAL EXCEPTION: main
01-03 13:28:25.612: E/AndroidRuntime(1276): java.lang.IllegalStateException: Could not find a method button(View) in the activity class com.sp.fragments.MainActivity for onClick handler on view class android.widget.Button with id 'f2_button' 
01-03 13:28:25.612: E/AndroidRuntime(1276): at android.view.View$1.onClick(View.java:3584) 
01-03 13:28:25.612: E/AndroidRuntime(1276): at android.view.View.performClick(View.java:4202) 
01-03 13:28:25.612: E/AndroidRuntime(1276): at android.view.View$PerformClick.run(View.java:17340) 
01-03 13:28:25.612: E/AndroidRuntime(1276): at android.os.Handler.handleCallback(Handler.java:725) 
01-03 13:28:25.612: E/AndroidRuntime(1276): at android.os.Handler.dispatchMessage(Handler.java:92) 
01-03 13:28:25.612: E/AndroidRuntime(1276): at android.os.Looper.loop(Looper.java:137) 
01-03 13:28:25.612: E/AndroidRuntime(1276): at android.app.ActivityThread.main(ActivityThread.java:5039) 
01-03 13:28:25.612: E/AndroidRuntime(1276): at java.lang.reflect.Method.invokeNative(Native Method) 
01-03 13:28:25.612: E/AndroidRuntime(1276): at java.lang.reflect.Method.invoke(Method.java:511) 
01-03 13:28:25.612: E/AndroidRuntime(1276): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 
01-03 13:28:25.612: E/AndroidRuntime(1276): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 
01-03 13:28:25.612: E/AndroidRuntime(1276): at dalvik.system.NativeStart.main(Native Method) 
01-03 13:28:25.612: E/AndroidRuntime(1276): Caused by: java.lang.NoSuchMethodException: button [class android.view.View] 
01-03 13:28:25.612: E/AndroidRuntime(1276): at java.lang.Class.getConstructorOrMethod(Class.java:460) 
01-03 13:28:25.612: E/AndroidRuntime(1276): at java.lang.Class.getMethod(Class.java:915) 
01-03 13:28:25.612: E/AndroidRuntime(1276): at android.view.View$1.onClick(View.java:3577) 
01-03 13:28:25.612: E/AndroidRuntime(1276): ... 11 more 
01-03 13:28:27.563: I/Process(1276): Sending signal. PID: 1276 SIG: 9

Answer 1

Activity:

If are having activity and if you define android:onClick attribute in XML then you just need to define a method with the same name in Activity.

Fragment:

But whenever you have Fragment and if you want to define click listener by just defining android:onClick attribute then you have to define a method with the same name in actual activity from where Fragment has been called.

OR you can simply implement a click listener programmatically.

Answer 2

You'll save yourself a lot of hassle by setting the onClickListener programmatically (instead of via XML). This should help you do what you're trying to do:

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    final View view = inflater.inflate(R.layout.second_fragment, container, false);
    final View button = view.findViewById(R.id.f2_button);
    button.setOnClickListener(
        new OnClickListener() {
            @Override
            public void onClick(View v) {
                /* DO SOMETHING UPON THE CLICK */
            }
        }
    );
    return view;
}

Answer 3

If you define onClick="button" in your .xml you need do define a method named public void button(View v) in the Activity which call the fragment, not in the fragment itself.

public class MainActivity extends FragmentActivity{

...

  public void button(View v){
    ...
  }

...

}

Answer 4

Your method button must be defined in MainActivity class.