我试着做一个有3个片段的选项卡式活动。我的一个片段有一个按钮，用于调用函数onclick:

<Button
    android:text="Start meeting"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginTop="58dp"
    android:id="@+id/sp_live_meeting"
    android:layout_below="@+id/live_cost"
    android:layout_centerHorizontal="true"
    android:onClick="sp_timer" />

片段是在相应的类文件中创建的：

public class LiveMeeting_meeting_fragment extends Fragment {

Button sp;
Button stop;
Chronometer chrono;
int cnt = 0;
long timeStop;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.livemeeting_meeting_fragment, container, false);
    sp = (Button) rootView.findViewById(R.id.sp_live_meeting);
    stop = (Button) rootView.findViewById(R.id.stop_live_meeting);
    chrono = (Chronometer) rootView.findViewById(R.id.live_timer);
    return rootView;
}

public void sp_timer(View view){
    if(cnt == 0){
        sp.setText("Pause meeting");
        chrono.setBase(SystemClock.elapsedRealtime() + timeStop);
        chrono.start();
        cnt = 1;
    } else if (cnt == 1){
        sp.setText("Continue meeting");
        chrono.stop();
        timeStop = chrono.getBase() - SystemClock.elapsedRealtime();
        cnt = 0;
    }

}
}

我现在的问题是，我不能调用函数，因为它告诉我它找不到函数：

java.lang.IllegalStateException: Could not find method sp_timer(View) in a parent or ancestor Context for android:onClick attribute defined on view class android.support.v7.widget.AppCompatButton with id 'sp_live_meeting'

我怎样才能解决这个问题？