为什么在XML中集成一个片段失败,错误消息是无法将片段转换为视图?

我想创建一个片段,我可以在多个活动中用作backbutton(我知道android有自己的backbutton,但对于我来说有一个特定的UI很重要)。

我尝试通过添加XML将backbutton集成到appcompatactivity中:

<android.support.v4.app.Fragment
    android:name="com.myapp.uielements.BackButton"
    android:id="@+id/backbutton"
    android:layout_height="wrap_content"
    android:layout_width="wrap_content"/>

后按钮的代码为:

import android.support.v4.app.Fragment;
...

public class BackButton extends Fragment {
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.backbutton, container, false);

        rootView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                getActivity().finish();
            }
        });

        return rootView;
    }
}

我得到错误:

 Caused by: android.view.InflateException: Binary XML file line #48: Binary XML file line #48: Class is not a View android.support.v4.app.Fragment
 Caused by: android.view.InflateException: Binary XML file line #48: Class is not a View android.support.v4.app.Fragment
 Caused by: java.lang.ClassCastException: class android.support.v4.app.Fragment cannot be cast to android.view.View