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);
}
}