Fragment详解系列一什么是Fragment

Fragment打算分成3个系列来讲。
系列一，讲解Fragment的基本用法，包括基本定义，Fragment的生命周期，Fragment的常用方法，Fragment的回退栈，Fragment和Activity之间的交互。
系列二，讲解ViewPager的基本用法及其原理。
系列三，讲解FragmentPagerAdapter 和 FragmentStatePagerAdapter使用及其原理，ViewPager和Fragment的完美结合。

---

以下开始讲解系列一。
谷歌推荐使用Fragment的一部分原因是因为重用性，一部分是因为Fragment用有自己的生命周期。重用性一种是Fragment切换可以实现不同效果，一种是因为手机密度、尺寸不同，可以在不同密度或者尺寸移动设备上使用不同的Fragment。Fragment有自己的生命周期，那么这些繁琐的过程就可以移到Fragment去处理了，这样Activity就可以高效清晰的处理其他事情。

一、初识Fragment的生命周期及其和Activity生命周期的关联。见以下流程图截图。

以上Fragment的生命周期分为三部分，初始化打开、暂停、销毁。
初始化运行结果：

FragmentActivity切到后台运行结果：

销毁运行结果：

通过以上流程图和代码运行结果能够清晰的理解Fragment、Activity二者的生命周期，及其二者生命周期的关联。但是，这里还是要提醒以下几点：
1、Activity、Fragment二者的生命周期顺序均是从上而下。
2、特别注意，当Activity的生命周期中的onStart走完之后，才会开始Fragment的生命周期，见流程图和执行结果。
3、当Fragment的 onstart执行完毕之后，才会去执行Activity的onResume，然后执行Fragment的onResume。

---

二、Fragment的基本方法，及其使用。
1、 FragmentManager manager = this.getSupportFragmentManager();
2、 FragmentTransaction transaction = manager.beginTransaction();
3、transaction.commit();

FragmentManager 用来管理和控制Fragment的一切动作。
FragmentTransaction 就是一个执行事务，在这个事务中可以对Fragment进行一系列操作，当transaction.commit()的时候则顺序执行定义的一系列操作。

4、transaction.add()。
增加一个Fragment。
5、transaction.remove() 。
删除一个Fragment，销毁视图。
6、transaction.replace()。
用一个Fragment替换掉另外一个Fragment，封装了remove，add过程。
7、transaction.hide()。
只是隐藏了当前Fragment，并没有销毁。
8、transaction.show()。
显示当前的Fragment。
9、attach()。
重建View的视图，附属到UI显示。
10、detach()。
将视图从UI剥离，但是视图实例并没有销毁掉，如果再次attach仍然可以显示。

以下对以上的方法应用提供一些代码做参考：

    public void createFragment(Fragment fragment, int handlerType){        FragmentManager manager = this.getSupportFragmentManager();        FragmentTransaction transaction = manager.beginTransaction();        if (handlerType == FragmentHandlerType.REPLACE){            transaction.replace(R.id.fragment_content, fragment);            transaction.addToBackStack(null);        }else if (handlerType == FragmentHandlerType.ADD){            transaction.add(R.id.fragment_content, fragment);        }else if (handlerType == FragmentHandlerType.HIDE){            transaction.hide(mFragmentOne);            transaction.add(R.id.fragment_content, fragment);            transaction.addToBackStack(null);        }        transaction.commit();    }

---

三、Fragment和Activity之间交互。

Fragment重在重用性，因此Fragment中不应该设计到具体的Activity实例，那么如果Fragment中执行的某些操作或者结果，如何反馈给Activity呢？

通过回调式借口的发方式来实现。参加一下代码和注释。

**Fragment中定义这样一个借口。**    /**     * This interface must be implemented by activities that contain this     * fragment to allow an interaction in this fragment to be communicated     * to the activity and potentially other fragments contained in that     * activity.     * <p>     * See the Android Training lesson <a href=     * "http://developer.android.com/training/basics/fragments/communicating.html"     * >Communicating with Other Fragments</a> for more information.     */    public interface OnFragmentInteractionListener {        // TODO: Update argument type and name        void onFragmentInteraction(Uri uri);    }

**FragmentActivity中实现这个接口。**public class FragmentActivity extends android.support.v4.app.FragmentActivity implements View.OnClickListener, FragmentOne.OnFragmentInteractionListener

Fragment中的onAttach中绑定接口的实现，这里就是Activity了。    @Override    public void onAttach(Context context) {        Log.d("FragmentTestOne: ", "onAttach");        System.out.println("FragmentTestOne: onAttach");        super.onAttach(context);        if (context instanceof OnFragmentInteractionListener) {            mListener = (OnFragmentInteractionListener) context;        } else {            throw new RuntimeException(context.toString()                    + " must implement OnFragmentInteractionListener");        }    }

参照以上代码，对Activity 和 Fragment之间的回调借口试的交互再解释下。（1）、Fragment 需要 定义一个借口，借口中有一些抽象方法；
（2）、Activity中需要实现Fragment 中定义的借口；
（3）、在Fragmen中的onAttach中因为传过来的有Context，而Context(Activity)已经实现了Fragment中定义的借口，因此在这里就可以绑定。那么，在Fragment需要和Activity之间进行交互的时候调用借口方法即可。

1、Acitivity 和 fragment 交互之前截图如下：

2、点击 “Activity 和 Fragment交互” 按钮，执行结果如下：

---

四、Fragment的回退栈。

和Activity任务栈一样，Fragment拥有自己的回退栈，如果即使通过addToBackStack将当前Fragment插入到回退栈中。这个回退栈是先进后出模式。

以下，通过代码运行结果图来解释Fragment回退栈。

1、启动Activity,界面如下，这里加载了第一个frgment：

2、在第一个Fragment文本框中输入以下字符，截图如下：

3、点击 “ToSecondFragmen” 按钮，执行结果如下：

4、点击回退，则回退到了第一个Fragment，截图如下：

以上的执行代码见以下源代码：

**3个Fragment切换按钮事件：**    public void onClick(View v) {        switch (v.getId()){            case R.id.change_fragment_one_button:                createFragment(mFragmentOne,  FragmentHandlerType.REPLACE);                break;            case R.id.change_fragment_two_button:                createFragment(mFragmentTwo,  FragmentHandlerType.HIDE);                break;            case R.id.change_fragment_three_button:                createFragment(mFragmentThree,  FragmentHandlerType.REPLACE);                break;            default:                break;        }    }

**点击按钮执行的函数：**    public void createFragment(Fragment fragment, int handlerType){        FragmentManager manager = this.getSupportFragmentManager();        FragmentTransaction transaction = manager.beginTransaction();        if (handlerType == FragmentHandlerType.REPLACE){            transaction.replace(R.id.fragment_content, fragment);            transaction.addToBackStack(null);        }else if (handlerType == FragmentHandlerType.ADD){            transaction.add(R.id.fragment_content, fragment);        }else if (handlerType == FragmentHandlerType.HIDE){            transaction.hide(mFragmentOne);            transaction.add(R.id.fragment_content, fragment);            transaction.addToBackStack(null);        }        transaction.commit();    }

如果跳转之前没有执行transaction.addToBackStack会怎样呢？ 如果没有则单击回退按钮回来后，则已经无法再显示上要给Fragment了。可以动手试试，这里就不截图了。

如果transaction.hide() 用 transaction.replace取代呢？ 则回退栈中也没有这个Fragment了，因为已经被销毁。

Fragment的详解之一先到这里，如果需要对Fragment更进一步学习，则参Fragment的详解之二 和 Fragment的详解之三。

以上系列一的所有源代码如下：

**activity_fragment.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:layout_gravity="center"    android:gravity="center"    android:orientation="vertical">    <LinearLayout        android:layout_width="match_parent"        android:layout_height="100px"        android:orientation="horizontal">        <Button            android:id="@+id/change_fragment_one_button"            android:layout_width="wrap_content"            android:layout_height="match_parent"            android:text="ToFirstFragment"/>        <Button            android:id="@+id/change_fragment_two_button"            android:layout_width="wrap_content"            android:layout_height="match_parent"            android:text="ToSecondFragment"/>        <Button            android:id="@+id/change_fragment_three_button"            android:layout_width="wrap_content"            android:layout_height="match_parent"            android:text="ToThreeFragment"/>    </LinearLayout>    <LinearLayout        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:orientation="vertical">        <TextView            android:id="@+id/interaction_text"            android:layout_width="match_parent"            android:layout_height="100px"            android:background="#ff0000"            android:text="初始化文字！"/>    </LinearLayout>    <TextView        android:layout_width="match_parent"        android:layout_height="100px"        android:background="#00ff00"        android:text="绿色区域上面是Activity中组件，下面是Fragment视图"/>    <FrameLayout        android:id="@+id/fragment_content"        android:layout_width="match_parent"        android:layout_height="match_parent">    </FrameLayout></LinearLayout>

**fragment_one.xml**<FrameLayout 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"    tools:context="com.example.kingsoft.FragmentUtil.FragmentOne">    <!-- TODO: Update blank fragment layout -->    <EditText        android:layout_width="match_parent"        android:layout_height="match_parent"        android:text="@string/first_fragment" /></FrameLayout>

**fragment_two.xml**<LinearLayout 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:orientation="vertical"    tools:context="com.example.kingsoft.FragmentUtil.FragmentTwo">    <Button        android:id="@+id/interaction_button"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="Activity和Fragment交互" />    <EditText        android:layout_width="match_parent"        android:layout_height="match_parent"        android:text="@string/two_fragment" /></LinearLayout>

**fragment_three.xml**<FrameLayout 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"    tools:context="com.example.kingsoft.FragmentUtil.FragmentThree">    <!-- TODO: Update blank fragment layout -->    <EditText        android:layout_width="match_parent"        android:layout_height="match_parent"        android:text="@string/three_fragment" /></FrameLayout>

**FragmentActivity.java**package com.example.kingsoft.FragmentUtil;import android.app.Activity;import android.net.Uri;import android.os.Bundle;import android.support.v4.app.Fragment;import android.support.v4.app.FragmentManager;import android.support.v4.app.FragmentTransaction;import android.view.View;import android.widget.Button;import android.widget.TextView;import com.example.kingsoft.CustomAdapter.R;public class FragmentActivity extends android.support.v4.app.FragmentActivity implements View.OnClickListener, FragmentOne.OnFragmentInteractionListener, FragmentThree.OnFragmentInteractionListener, FragmentTwo.OnFragmentInteractionListener{    public static int counter = 0;    private Button mOne = null;    private Button mTwo = null;    private Button mThree = null;    private Fragment mFragmentOne = null;    private Fragment mFragmentTwo = null;    private Fragment mFragmentThree = null;    private TextView mTextView = null;    @Override    protected void onCreate(Bundle savedInstanceState) {        System.out.println("FragmentTestActivity: onCreate");        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_fragment);        initCompoment();    }    @Override    protected void onStart() {        System.out.println("FragmentTestActivity: onStart");        super.onStart();    }    @Override    protected void onRestoreInstanceState(Bundle savedInstanceState) {        System.out.println("FragmentTestActivity: onRestoreInstanceState");        super.onRestoreInstanceState(savedInstanceState);    }    @Override    protected void onResume() {        System.out.println("FragmentTestActivity: onResume");        super.onResume();    }    @Override    protected void onRestart() {        System.out.println("FragmentTestActivity: onRestart");        super.onRestart();    }    @Override    protected void onPause() {        System.out.println("FragmentTestActivity: onPause");        super.onPause();    }    @Override    protected void onSaveInstanceState(Bundle outState) {        System.out.println("FragmentTestActivity: onSaveInstanceState");        super.onSaveInstanceState(outState);    }    @Override    protected void onStop() {        System.out.println("FragmentTestActivity: onStop");        super.onStop();    }    @Override    protected void onDestroy() {        System.out.println("FragmentTestActivity: onDestroy");        super.onDestroy();    }    public void initCompoment(){        mFragmentOne = new FragmentOne();        createFragment(mFragmentOne, FragmentHandlerType.ADD);        mFragmentTwo = new FragmentTwo();        mFragmentThree = new FragmentThree();        mOne = (Button)findViewById(R.id.change_fragment_one_button);        mTwo = (Button)findViewById(R.id.change_fragment_two_button);        mThree = (Button)findViewById(R.id.change_fragment_three_button);        mOne.setOnClickListener(this);        mTwo.setOnClickListener(this);        mThree.setOnClickListener(this);        mTextView = (TextView)findViewById(R.id.interaction_text);    }    public void createFragment(Fragment fragment, int handlerType){        FragmentManager manager = this.getSupportFragmentManager();        FragmentTransaction transaction = manager.beginTransaction();        if (handlerType == FragmentHandlerType.REPLACE){            transaction.replace(R.id.fragment_content, fragment);            transaction.addToBackStack(null);        }else if (handlerType == FragmentHandlerType.ADD){            transaction.add(R.id.fragment_content, fragment);        }else if (handlerType == FragmentHandlerType.HIDE){            transaction.hide(mFragmentOne);            transaction.add(R.id.fragment_content, fragment);            transaction.addToBackStack(null);        }        transaction.commit();    }    /**     * Called when a view has been clicked.     *     * @param v The view that was clicked.     */    @Override    public void onClick(View v) {        switch (v.getId()){            case R.id.change_fragment_one_button:                createFragment(mFragmentOne,  FragmentHandlerType.REPLACE);                break;            case R.id.change_fragment_two_button:                createFragment(mFragmentTwo,  FragmentHandlerType.HIDE);                break;            case R.id.change_fragment_three_button:                createFragment(mFragmentThree,  FragmentHandlerType.REPLACE);                break;            default:                break;        }    }    @Override    public void onFragmentInteraction(Uri uri) {    }    @Override    public void onFragmentInteraction(String message) {        mTextView.setText(message);        mTextView.requestLayout();    }    public static class FragmentHandlerType{        public static final int ADD = counter++;        public static final int REPLACE = counter++;        public static final int HIDE = counter++;    }}

**FragmentOne.java**package com.example.kingsoft.FragmentUtil;import android.content.Context;import android.net.Uri;import android.os.Bundle;import android.support.annotation.Nullable;import android.support.v4.app.Fragment;import android.util.Log;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;import com.example.kingsoft.CustomAdapter.R;public class FragmentOne extends Fragment {    // TODO: Rename parameter arguments, choose names that match    // the fragment initialization parameters, e.g. ARG_ITEM_NUMBER    private static final String ARG_PARAM1 = "param1";    private static final String ARG_PARAM2 = "param2";    // TODO: Rename and change types of parameters    private String mParam1;    private String mParam2;    private OnFragmentInteractionListener mListener;    public FragmentOne() {        // Required empty public constructor    }    /**     * Use this factory method to create a new instance of     * this fragment using the provided parameters.     *     * @param param1 Parameter 1.     * @param param2 Parameter 2.     * @return A new instance of fragment FragmentTestOne.     */    // TODO: Rename and change types and number of parameters    public static FragmentOne newInstance(String param1, String param2) {        FragmentOne fragment = new FragmentOne();        Bundle args = new Bundle();        args.putString(ARG_PARAM1, param1);        args.putString(ARG_PARAM2, param2);        fragment.setArguments(args);        return fragment;    }    @Override    public void onAttach(Context context) {        Log.d("FragmentTestOne: ", "onAttach");        System.out.println("FragmentTestOne: onAttach");        super.onAttach(context);        if (context instanceof OnFragmentInteractionListener) {            mListener = (OnFragmentInteractionListener) context;        } else {            throw new RuntimeException(context.toString()                    + " must implement OnFragmentInteractionListener");        }    }    @Override    public void onCreate(Bundle savedInstanceState) {        Log.d("FragmentTestOne: ", "onCreate");        System.out.println("FragmentTestOne: onCreate");        super.onCreate(savedInstanceState);        if (getArguments() != null) {            mParam1 = getArguments().getString(ARG_PARAM1);            mParam2 = getArguments().getString(ARG_PARAM2);        }    }    @Override    public View onCreateView(LayoutInflater inflater, ViewGroup container,                             Bundle savedInstanceState) {        Log.d("FragmentTestOne: ", "onCreateView");        System.out.println("FragmentTestOne: onCreateView");        // Inflate the layout for this fragment        return inflater.inflate(R.layout.fragment_one, container, false);    }    @Override    public void onActivityCreated(@Nullable Bundle savedInstanceState) {        Log.d("FragmentTestOne: ", "onActivityCreated");        System.out.println("FragmentTestOne: onActivityCreated");        super.onActivityCreated(savedInstanceState);    }    @Override    public void onStart() {        Log.d("FragmentTestOne: ", "onStart");        System.out.println("FragmentTestOne: onStart");        super.onStart();    }    @Override    public void onResume() {        Log.d("FragmentTestOne: ", "onResume");        System.out.println("FragmentTestOne: onResume");        super.onResume();    }    @Override    public void onSaveInstanceState(Bundle outState) {        System.out.println("FragmentTestOne: onSaveInstanceState");        super.onSaveInstanceState(outState);    }    @Override    public void onPause() {        Log.d("FragmentTestOne: ", "onPause");        System.out.println("FragmentTestOne: onPause");        super.onPause();    }    @Override    public void onStop() {        Log.d("FragmentTestOne: ", "onStop");        System.out.println("FragmentTestOne: onStop");        super.onStop();    }    @Override    public void onDestroyView() {        Log.d("FragmentTestOne: ", "onDestroyView");        System.out.println("FragmentTestOne: onDestroyView");        super.onDestroyView();    }    @Override    public void onDestroy() {        Log.d("FragmentTestOne: ", "onDestroy");        System.out.println("FragmentTestOne: onDestroy");        super.onDestroy();    }    @Override    public void onDetach() {        Log.d("FragmentTestOne: ", "onDetach");        System.out.println("FragmentTestOne: onDetach");        super.onDetach();        mListener = null;    }    // TODO: Rename method, update argument and hook method into UI event    public void onButtonPressed(Uri uri) {        if (mListener != null) {            mListener.onFragmentInteraction(uri);        }    }    /**     * This interface must be implemented by activities that contain this     * fragment to allow an interaction in this fragment to be communicated     * to the activity and potentially other fragments contained in that     * activity.     * <p>     * See the Android Training lesson <a href=     * "http://developer.android.com/training/basics/fragments/communicating.html"     * >Communicating with Other Fragments</a> for more information.     */    public interface OnFragmentInteractionListener {        // TODO: Update argument type and name        void onFragmentInteraction(Uri uri);    }}

**FragmentTwo.java**package com.example.kingsoft.FragmentUtil;import android.content.Context;import android.net.Uri;import android.os.Bundle;import android.support.v4.app.Fragment;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;import android.widget.Button;import com.example.kingsoft.CustomAdapter.R;/** * A simple {@link Fragment} subclass. * Activities that contain this fragment must implement the * {@link FragmentTwo.OnFragmentInteractionListener} interface * to handle interaction events. * Use the {@link FragmentTwo#newInstance} factory method to * create an instance of this fragment. */public class FragmentTwo extends Fragment {    // TODO: Rename parameter arguments, choose names that match    // the fragment initialization parameters, e.g. ARG_ITEM_NUMBER    private static final String ARG_PARAM1 = "param1";    private static final String ARG_PARAM2 = "param2";    // TODO: Rename and change types of parameters    private String mParam1;    private String mParam2;    private OnFragmentInteractionListener mListener;    private Button mButton = null;    public FragmentTwo() {        // Required empty public constructor    }    /**     * Use this factory method to create a new instance of     * this fragment using the provided parameters.     *     * @param param1 Parameter 1.     * @param param2 Parameter 2.     * @return A new instance of fragment FragmentTwo.     */    // TODO: Rename and change types and number of parameters    public static FragmentTwo newInstance(String param1, String param2) {        FragmentTwo fragment = new FragmentTwo();        Bundle args = new Bundle();        args.putString(ARG_PARAM1, param1);        args.putString(ARG_PARAM2, param2);        fragment.setArguments(args);        return fragment;    }    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        if (getArguments() != null) {            mParam1 = getArguments().getString(ARG_PARAM1);            mParam2 = getArguments().getString(ARG_PARAM2);        }    }    @Override    public View onCreateView(LayoutInflater inflater, ViewGroup container,                             Bundle savedInstanceState) {        // Inflate the layout for this fragment        View view = inflater.inflate(R.layout.fragment_two, container, false);        mButton = (Button)view.findViewById(R.id.interaction_button);        mButton.setOnClickListener((v) -> {            mListener.onFragmentInteraction("this message come from FragmentTwo!");        });        return view;    }    // TODO: Rename method, update argument and hook method into UI event    public void onButtonPressed(String message) {        if (mListener != null) {            mListener.onFragmentInteraction(message);        }    }    @Override    public void onAttach(Context context) {        super.onAttach(context);        if (context instanceof OnFragmentInteractionListener) {            mListener = (OnFragmentInteractionListener) context;        } else {            throw new RuntimeException(context.toString()                    + " must implement OnFragmentInteractionListener");        }    }    @Override    public void onDetach() {        super.onDetach();        mListener = null;    }    /**     * This interface must be implemented by activities that contain this     * fragment to allow an interaction in this fragment to be communicated     * to the activity and potentially other fragments contained in that     * activity.     * <p>     * See the Android Training lesson <a href=     * "http://developer.android.com/training/basics/fragments/communicating.html"     * >Communicating with Other Fragments</a> for more information.     */    public interface OnFragmentInteractionListener {        // TODO: Update argument type and name        void onFragmentInteraction(String message);    }}

**FragmentThree .java**package com.example.kingsoft.FragmentUtil;import android.content.Context;import android.net.Uri;import android.os.Bundle;import android.support.v4.app.Fragment;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;import com.example.kingsoft.CustomAdapter.R;/** * A simple {@link Fragment} subclass. * Activities that contain this fragment must implement the * {@link FragmentThree.OnFragmentInteractionListener} interface * to handle interaction events. * Use the {@link FragmentThree#newInstance} factory method to * create an instance of this fragment. */public class FragmentThree extends Fragment {    // TODO: Rename parameter arguments, choose names that match    // the fragment initialization parameters, e.g. ARG_ITEM_NUMBER    private static final String ARG_PARAM1 = "param1";    private static final String ARG_PARAM2 = "param2";    // TODO: Rename and change types of parameters    private String mParam1;    private String mParam2;    private OnFragmentInteractionListener mListener;    public FragmentThree() {        // Required empty public constructor    }    /**     * Use this factory method to create a new instance of     * this fragment using the provided parameters.     *     * @param param1 Parameter 1.     * @param param2 Parameter 2.     * @return A new instance of fragment FragmentThree.     */    // TODO: Rename and change types and number of parameters    public static FragmentThree newInstance(String param1, String param2) {        FragmentThree fragment = new FragmentThree();        Bundle args = new Bundle();        args.putString(ARG_PARAM1, param1);        args.putString(ARG_PARAM2, param2);        fragment.setArguments(args);        return fragment;    }    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        if (getArguments() != null) {            mParam1 = getArguments().getString(ARG_PARAM1);            mParam2 = getArguments().getString(ARG_PARAM2);        }    }    @Override    public View onCreateView(LayoutInflater inflater, ViewGroup container,                             Bundle savedInstanceState) {        // Inflate the layout for this fragment        return inflater.inflate(R.layout.fragment_three, container, false);    }    // TODO: Rename method, update argument and hook method into UI event    public void onButtonPressed(Uri uri) {        if (mListener != null) {            mListener.onFragmentInteraction(uri);        }    }    @Override    public void onAttach(Context context) {        super.onAttach(context);        if (context instanceof OnFragmentInteractionListener) {            mListener = (OnFragmentInteractionListener) context;        } else {            throw new RuntimeException(context.toString()                    + " must implement OnFragmentInteractionListener");        }    }    @Override    public void onDetach() {        super.onDetach();        mListener = null;    }    /**     * This interface must be implemented by activities that contain this     * fragment to allow an interaction in this fragment to be communicated     * to the activity and potentially other fragments contained in that     * activity.     * <p>     * See the Android Training lesson <a href=     * "http://developer.android.com/training/basics/fragments/communicating.html"     * >Communicating with Other Fragments</a> for more information.     */    public interface OnFragmentInteractionListener {        // TODO: Update argument type and name        void onFragmentInteraction(Uri uri);    }}