A file template for creating a headless Fragment. The attach() methods add the fragment to the parent if it doesn't already exist and returns the attached fragment. The methods ensure that the parent implements the parent interface. If needed, parameters may be added to the attach() methods to supply fragment arguments.

HeadlessFragment.java

#if (${PACKAGE_NAME} && ${PACKAGE_NAME} != "")package ${PACKAGE_NAME};#end

import android.app.Activity;
import android.app.Fragment;
import android.app.FragmentManager;

#parse("File Header.java")
public class ${NAME} extends Fragment {
    
  private static final String FRAG_TAG = ${NAME}.class.getCanonicalName();
  
  public interface ${PARENT_INTERFACE} {
    //TODO: define methods for parent interface
  }

  public static <ParentFrag extends Fragment & ${PARENT_INTERFACE}> ${NAME} attach(ParentFrag parent) {
    return attach(parent.getChildFragmentManager());
  }

  public static <ParentActivity extends Activity & ${PARENT_INTERFACE}> ${NAME} attach(ParentActivity parent) {
    return attach(parent.getFragmentManager());
  }

  private static ${NAME} attach(FragmentManager fragmentManager) {
    ${NAME} frag = (${NAME}) fragmentManager.findFragmentByTag(FRAG_TAG);
    if (frag == null) {
      frag = new ${NAME}();
      fragmentManager.beginTransaction().add(frag, FRAG_TAG).commit();
    }
    return frag;
  }

  private ${PARENT_INTERFACE} getParent() {
    Fragment parentFragment = getParentFragment();
    if (parentFragment instanceof ${PARENT_INTERFACE}) {
      return (${PARENT_INTERFACE}) parentFragment;
    } else {
      Activity activity = getActivity();
      if (activity instanceof ${PARENT_INTERFACE}) {
        return (${PARENT_INTERFACE}) activity;
      }
    }
    return null;
  }
}

LICENSE

Copyright 2015 Joshua Brown

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

I do not understand what it is to do,can you give me an example?

amazing idea!!!,How you can think that!!! Is lots of fragment can affect activity performance?