学而不思则罔，思而不学则殆

【Android】Fragment简单初识

前言Demo用法1.xml注册2.动态添加Fragment3.在Fragment中实现返回栈 Activity和Fragment通信Activity发送给Fragment使用Bundle来传递数据1.在Activity中绑定数据到Fragment上2.在Fragment中拿到Bundle对象3.效果 Fragment把数据传递给Activity1.使用Activity对象效果 2.使用回调接口1.在需要发送数据的一边中添加内部接口（这里仅以RightFragment为例）2.在Activity实现接口3.效果 生命周期学习通过add添加两个Fragment通过add 添加两个Fragment并且加入到返回栈中通过replace添加两个Fragment通过replace添加两个Fragment并且添加返回栈测试hide和show

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前言

Fragment是一种可以嵌套在Activity当中的UI片段。

Demo

https://github.com/aJanefish/FragmentDemo

用法

1.xml注册

1.自定义Fragment

//left_fragment.xml <?xml version="1.0" encoding="utf-8"?> <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:background="@color/gray"> <Button android:id="@+id/left_fragment_button" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="我是左fragment" /> </androidx.constraintlayout.widget.ConstraintLayout> //LeftFragment.java public class LeftFragment extends Fragment { @Nullable @Override public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) { return inflater.inflate(R.layout.left_fragment, container, false); } } //right_fragment.xml <?xml version="1.0" encoding="utf-8"?> <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:background="@color/colorAccent"> <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="我是右边的fragment" /> </androidx.constraintlayout.widget.ConstraintLayout> //RightFragment .java public class RightFragment extends Fragment { @Nullable @Override public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) { return inflater.inflate(R.layout.right_fragment, container, false); } }

2.布局中注册两个fragment 通过{android:name}引用Fragment

<?xml version="1.0" encoding="utf-8"?> <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="horizontal" tools:context=".activity.XmlActivity"> <fragment android:id="@+id/activity_xml_left" android:name="com.example.fragmentdemo.fragment.LeftFragment" android:layout_width="0dp" android:layout_height="match_parent" android:layout_weight="1" /> <fragment android:id="@+id/activity_xml_right" android:name="com.example.fragmentdemo.fragment.RightFragment" android:layout_width="0dp" android:layout_height="match_parent" android:layout_weight="1" /> </LinearLayout>

3.展示效果

2.动态添加Fragment

1.在自定义一个Fragment

//another_right_fragment.xml <?xml version="1.0" encoding="utf-8"?> <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:background="@color/colorAccent"> <Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="我另一个Fragment" /> </androidx.constraintlayout.widget.ConstraintLayout> //AnotherRightFragment.java public class AnotherRightFragment extends Fragment { @Nullable @Override public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) { return inflater.inflate(R.layout.another_right_fragment, container, false); } }

2.定义容器

<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="horizontal" tools:context=".activity.JavaUseFragmentActivity"> <fragment android:id="@+id/activity_java_use_fragment_left" android:name="com.example.fragmentdemo.fragment.LeftFragment" android:layout_width="0dp" android:layout_height="match_parent" android:layout_weight="1" /> <!--Fragment的容器--> <FrameLayout android:id="@+id/activity_java_use_fragment_fl" android:layout_width="0dp" android:layout_height="match_parent" android:layout_weight="1" /> </LinearLayout>

3.动态替换fragment

public class JavaUseFragmentActivity extends AppCompatActivity { boolean flag = false; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_java_use_fragment); Button button = findViewById(R.id.left_fragment_button); button.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { if (flag) { replaceFragment(new AnotherRightFragment()); } else { replaceFragment(new RightFragment()); } flag = !flag; } }); } private void replaceFragment(Fragment fragment) { //获取FragmentManager FragmentManager fragmentManager = getSupportFragmentManager(); //开启一个事务 FragmentTransaction beginTransaction = fragmentManager.beginTransaction(); //向容器添加或者替换Fragment beginTransaction.replace(R.id.activity_java_use_fragment_fl, fragment); //提交事务 beginTransaction.commit(); } }

动态添加Fragment主要分为5步:

创建一个Fragment的实例获取FragmentManager开启一个事务向容器添加或者替换Fragment提交事务

效果如下： 开始时容器中没有Fragment,效果为1，点击后添加Fragment到容器中了，就是2 和 3的切换

3.在Fragment中实现返回栈

在上一节的测试中，实现了向Activity中动态添加Fragment的功能。不过你尝试一下就会发现。通过点击按钮添加了一个Fragment之后，这是按下返回键，该页面就会自动退出。如果我们想实现类似返回栈的效果，按下Back键后，回到上一个Fragment，该如何实现呢？ 其实很简单，FragmentTransaction 中提供了addToBackStack()方法，可以用于将一个事务添加到返回栈中。代码如下：

private void replaceFragment(Fragment fragment) { //获取FragmentManager FragmentManager fragmentManager = getSupportFragmentManager(); //开启一个事务 FragmentTransaction beginTransaction = fragmentManager.beginTransaction(); //向容器添加或者替换Fragment beginTransaction.replace(R.id.activity_java_use_fragment_fl, fragment); //加入返回栈 beginTransaction.addToBackStack(null); //提交事务 beginTransaction.commit(); }

这里我们在事务提交之前调用了addToBackStack方法，他可以接收一个名字用于描述返回栈的状态，一般传入null即可。现在重新运行程序，并点击按钮两次，会添加RightFragment和AnotherRightFragment两个到容器中，然后按下返回键，这个时候并没有退出Activity，而是回到了RightFragment。继续按下返回键，RightFragment界面也会消失，容器为空。再次按下返回键，页面才会退出。

Activity和Fragment通信

Activity发送给Fragment

使用Bundle来传递数据

1.在Activity中绑定数据到Fragment上

这是一个点击事件：

boolean flag = false; public void interactionActivityTest(View view) { if (flag) { AnotherRightFragment anotherRightFragment = new AnotherRightFragment(); Bundle bundle = new Bundle(); long now = System.currentTimeMillis(); Log.d("zhangyu20201012", "interactionActivityTest start AnotherRightFragment now:" + now); bundle.putString("testKey", "" + now); anotherRightFragment.setArguments(bundle); replaceFragment(anotherRightFragment); } else { RightFragment rightFragment = new RightFragment(); Bundle bundle = new Bundle(); long now = System.currentTimeMillis(); Log.d("zhangyu20201012", "interactionActivityTest start RightFragment now:" + now); bundle.putString("testKey", "" + now); rightFragment.setArguments(bundle); replaceFragment(rightFragment); } flag = !flag; }

2.在Fragment中拿到Bundle对象

//RightFragment.java //AnotherRightFragment.java @Override public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) { super.onViewCreated(view, savedInstanceState); TextView des = view.findViewById(R.id.right_fragment_des); Bundle bundle = getArguments(); if (bundle != null) { String testKey = bundle.getString("testKey"); des.setText("來自Activity的信息："+testKey); } }

3.效果

Fragment把数据传递给Activity

1.使用Activity对象

public class InteractionActivity extends AppCompatActivity { private TextView des; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_interaction); des = findViewById(R.id.activity_interaction_des); } ... //接收Fragment的调用 public void testDes(String msg) { des.setText(msg); } } public class RightFragment extends Fragment { ... @Override public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) { super.onViewCreated(view, savedInstanceState); TextView des = view.findViewById(R.id.right_fragment_des); Bundle bundle = getArguments(); if (bundle != null) { String testKey = bundle.getString("testKey"); des.setText("來自Activity的信息：" + testKey); } final FragmentActivity activity = getActivity(); Log.d("zhangyu20201012", "RightFragment onViewCreated:" + activity); Button button = view.findViewById(R.id.right_fragment_button); button.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { if (activity instanceof InteractionActivity) { ((InteractionActivity) activity).testDes("我是来自RightFragment的信息"); } } }); } } public class AnotherRightFragment extends Fragment { ... @Override public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) { super.onViewCreated(view, savedInstanceState); TextView des = view.findViewById(R.id.another_right_fragment_des); Bundle bundle = getArguments(); if (bundle != null) { String testKey = bundle.getString("testKey"); des.setText("來自Activity的信息：" + testKey); } final FragmentActivity activity = getActivity(); Log.d("zhangyu20201012", "AnotherRightFragment onViewCreated:" + activity); Button button = view.findViewById(R.id.another_right_fragment_button); button.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { if (activity instanceof InteractionActivity) { ((InteractionActivity) activity).testDes("我是来自AnotherRightFragment的信息"); } } }); } }

效果

2.使用回调接口

1.在需要发送数据的一边中添加内部接口（这里仅以RightFragment为例）

public class RightFragment extends Fragment { private OnMsgChangeListener msgChangeListener; ... @Override public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) { super.onViewCreated(view, savedInstanceState); TextView des = view.findViewById(R.id.right_fragment_des); Bundle bundle = getArguments(); if (bundle != null) { String testKey = bundle.getString("testKey"); des.setText("來自Activity的信息：" + testKey); } final FragmentActivity activity = getActivity(); Log.d("zhangyu20201012", "RightFragment onViewCreated:" + activity); Button button = view.findViewById(R.id.right_fragment_button); button.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { // if (activity instanceof InteractionActivity) { // ((InteractionActivity) activity).testDes("我是来自RightFragment的信息"); // } if (msgChangeListener != null) { msgChangeListener.msgChange("我是来自RightFragment的信息,通过接口"); } } }); } /** * 内部接口 */ public interface OnMsgChangeListener { void msgChange(String msg); } public void setMsgChangeListener(OnMsgChangeListener msgChangeListener) { this.msgChangeListener = msgChangeListener; } }

2.在Activity实现接口

public class InteractionActivity extends AppCompatActivity implements RightFragment.OnMsgChangeListener { private TextView des; ... boolean flag = false; public void interactionActivityTest(View view) { if (flag) { AnotherRightFragment anotherRightFragment = new AnotherRightFragment(); Bundle bundle = new Bundle(); long now = System.currentTimeMillis(); Log.d("zhangyu20201012", "interactionActivityTest start AnotherRightFragment now:" + now); bundle.putString("testKey", "" + now); anotherRightFragment.setArguments(bundle); replaceFragment(anotherRightFragment); } else { RightFragment rightFragment = new RightFragment(); rightFragment.setMsgChangeListener(this); //注册接口 Bundle bundle = new Bundle(); long now = System.currentTimeMillis(); Log.d("zhangyu20201012", "interactionActivityTest start RightFragment now:" + now); bundle.putString("testKey", "" + now); rightFragment.setArguments(bundle); replaceFragment(rightFragment); } flag = !flag; } public void testDes(String msg) { des.setText(msg); } @Override public void msgChange(String msg) { des.setText(msg); } }

3.效果

生命周期学习

新建一个新的BaseFragment类，在关键的生命周期方法内打印生命周期的信息：

public class BaseFragment extends Fragment { String getTAG() { return "zhangyu1027-" + this.getClass().getSimpleName(); } @Override public void onAttach(@NonNull Context context) { super.onAttach(context); Log.d(getTAG(), "onAttach " + this.hashCode()); } @Override public void onCreate(@Nullable Bundle savedInstanceState) { super.onCreate(savedInstanceState); Log.d(getTAG(), "onCreate " + this.hashCode()); } @Nullable @Override public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) { Log.d(getTAG(), "onCreateView " + this.hashCode()); return super.onCreateView(inflater, container, savedInstanceState); } @Override public void onActivityCreated(@Nullable Bundle savedInstanceState) { super.onActivityCreated(savedInstanceState); Log.d(getTAG(), "onActivityCreated " + this.hashCode()); } @Override public void onStart() { super.onStart(); Log.d(getTAG(), "onStart " + this.hashCode()); } @Override public void onResume() { super.onResume(); Log.d(getTAG(), "onResume " + this.hashCode()); } @Override public void onPause() { super.onPause(); Log.d(getTAG(), "onPause " + this.hashCode()); } @Override public void onStop() { super.onStop(); Log.d(getTAG(), "onStop " + this.hashCode()); } @Override public void onDestroyView() { super.onDestroyView(); Log.d(getTAG(), "onDestroyView " + this.hashCode()); } @Override public void onDestroy() { super.onDestroy(); Log.d(getTAG(), "onDestroy " + this.hashCode()); } @Override public void onDetach() { super.onDetach(); Log.d(getTAG(), "onDetach " + this.hashCode()); } }

通过add添加两个Fragment

2020-10-27 08:07:14.802 15760-15760/com.example.fragmentdemo D/zhangyu1027-RightFragment: onAttach 44450868 2020-10-27 08:07:14.802 15760-15760/com.example.fragmentdemo D/zhangyu1027-RightFragment: onCreate 44450868 2020-10-27 08:07:14.802 15760-15760/com.example.fragmentdemo D/zhangyu1027-RightFragment: onCreateView 44450868 2020-10-27 08:07:14.810 15760-15760/com.example.fragmentdemo D/zhangyu1027-RightFragment: onActivityCreated 44450868 2020-10-27 08:07:14.811 15760-15760/com.example.fragmentdemo D/zhangyu1027-RightFragment: onStart 44450868 2020-10-27 08:07:14.811 15760-15760/com.example.fragmentdemo D/zhangyu1027-RightFragment: onResume 44450868 2020-10-27 08:07:15.383 15760-15760/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onAttach 227039740 2020-10-27 08:07:15.383 15760-15760/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onCreate 227039740 2020-10-27 08:07:15.384 15760-15760/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onCreateView 227039740 2020-10-27 08:07:15.394 15760-15760/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onActivityCreated 227039740 2020-10-27 08:07:15.394 15760-15760/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onStart 227039740 2020-10-27 08:07:15.394 15760-15760/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onResume 227039740

生命周期为：【onAttach -> onCreate -> onCreateView -> onActivityCreated -> onStart -> onResume 】 点击返回键：

2020-10-27 08:07:17.130 15760-15760/com.example.fragmentdemo D/zhangyu1027-RightFragment: onPause 44450868 2020-10-27 08:07:17.130 15760-15760/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onPause 227039740 2020-10-27 08:07:17.784 15760-15760/com.example.fragmentdemo D/zhangyu1027-RightFragment: onStop 44450868 2020-10-27 08:07:17.784 15760-15760/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onStop 227039740 2020-10-27 08:07:17.786 15760-15760/com.example.fragmentdemo D/zhangyu1027-RightFragment: onDestroyView 44450868 2020-10-27 08:07:17.787 15760-15760/com.example.fragmentdemo D/zhangyu1027-RightFragment: onDestroy 44450868 2020-10-27 08:07:17.787 15760-15760/com.example.fragmentdemo D/zhangyu1027-RightFragment: onDetach 44450868 2020-10-27 08:07:17.787 15760-15760/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onDestroyView 227039740 2020-10-27 08:07:17.788 15760-15760/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onDestroy 227039740 2020-10-27 08:07:17.788 15760-15760/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onDetach 227039740

点击返回键，页面全部一下退出，通过add添加的两个Fragment都直接全部退出。生命周期为： 【onPause -> onStop -> onDestroyView-> onDestroy -> onDetach】，两个Fragment生命周期之间存在交叉。

通过add 添加两个Fragment并且加入到返回栈中

private void transactionFragment(Fragment fragment) { //获取FragmentManager FragmentManager fragmentManager = getSupportFragmentManager(); //开启一个事务 FragmentTransaction beginTransaction = fragmentManager.beginTransaction(); //向容器添加或者替换Fragment beginTransaction.add(R.id.activity_life_cycle_fl, fragment); //加入返回栈 beginTransaction.addToBackStack(null); //提交事务 beginTransaction.commit(); }

先添加两个Fragment,生命周期如下： 生命周期为：【onAttach -> onCreate -> onCreateView -> onActivityCreated -> onStart -> onResume 】

2020-10-27 08:09:48.911 15977-15977/com.example.fragmentdemo D/zhangyu1027-RightFragment: onAttach 245832902 2020-10-27 08:09:48.911 15977-15977/com.example.fragmentdemo D/zhangyu1027-RightFragment: onCreate 245832902 2020-10-27 08:09:48.914 15977-15977/com.example.fragmentdemo D/zhangyu1027-RightFragment: onCreateView 245832902 2020-10-27 08:09:48.923 15977-15977/com.example.fragmentdemo D/zhangyu1027-RightFragment: onActivityCreated 245832902 2020-10-27 08:09:48.923 15977-15977/com.example.fragmentdemo D/zhangyu1027-RightFragment: onStart 245832902 2020-10-27 08:09:48.924 15977-15977/com.example.fragmentdemo D/zhangyu1027-RightFragment: onResume 245832902 2020-10-27 08:09:50.965 15977-15977/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onAttach 22956878 2020-10-27 08:09:50.965 15977-15977/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onCreate 22956878 2020-10-27 08:09:50.965 15977-15977/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onCreateView 22956878 2020-10-27 08:09:50.977 15977-15977/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onActivityCreated 22956878 2020-10-27 08:09:50.977 15977-15977/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onStart 22956878 2020-10-27 08:09:50.978 15977-15977/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onResume 22956878

这个时候点击返回键，会先回到上一个Fragment，再点击一次放回键才会退出页面。 生命周期为：【onPause -> onStop -> onDestroyView-> onDestroy -> onDetach】，两个Fragment生命周期没有交叉。

2020-10-27 08:09:52.413 15977-15977/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onPause 22956878 2020-10-27 08:09:52.414 15977-15977/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onStop 22956878 2020-10-27 08:09:52.414 15977-15977/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onDestroyView 22956878 2020-10-27 08:09:52.419 15977-15977/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onDestroy 22956878 2020-10-27 08:09:52.419 15977-15977/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onDetach 22956878 2020-10-27 08:09:56.423 15977-15977/com.example.fragmentdemo D/zhangyu1027-RightFragment: onPause 245832902 2020-10-27 08:09:56.423 15977-15977/com.example.fragmentdemo D/zhangyu1027-RightFragment: onStop 245832902 2020-10-27 08:09:56.423 15977-15977/com.example.fragmentdemo D/zhangyu1027-RightFragment: onDestroyView 245832902 2020-10-27 08:09:56.424 15977-15977/com.example.fragmentdemo D/zhangyu1027-RightFragment: onDestroy 245832902 2020-10-27 08:09:56.425 15977-15977/com.example.fragmentdemo D/zhangyu1027-RightFragment: onDetach 245832902

通过replace添加两个Fragment

private void transactionFragment(Fragment fragment) { //获取FragmentManager FragmentManager fragmentManager = getSupportFragmentManager(); //开启一个事务 FragmentTransaction beginTransaction = fragmentManager.beginTransaction(); //向容器添加或者替换Fragment beginTransaction.replace(R.id.activity_life_cycle_fl, fragment); //加入返回栈 //beginTransaction.addToBackStack(null); //提交事务 beginTransaction.commit(); }

先添加RightFragment，生命周期跟之前一样：【onAttach -> onCreate -> onCreateView -> onActivityCreated -> onStart -> onResume 】 当时呢，当我们添加AnotherRightFragment的时候，AnotherRightFragment的生命周期为先是【onAttach -》onCreate 】，接着RightFragment直接走销毁的生命周期：【onPause -> onStop -> onDestroyView-> onDestroy -> onDetach】。 然后AnotherRightFragment走【onCreateView -> onActivityCreated -> onStart -> onResume】

2020-10-27 08:17:57.397 16178-16178/com.example.fragmentdemo D/zhangyu1027: LifeCycleActivity onCreate127615966 2020-10-27 08:17:58.924 16178-16178/com.example.fragmentdemo D/zhangyu1027-RightFragment: onAttach 182829729 2020-10-27 08:17:58.924 16178-16178/com.example.fragmentdemo D/zhangyu1027-RightFragment: onCreate 182829729 2020-10-27 08:17:58.925 16178-16178/com.example.fragmentdemo D/zhangyu1027-RightFragment: onCreateView 182829729 2020-10-27 08:17:58.944 16178-16178/com.example.fragmentdemo D/zhangyu1027-RightFragment: onActivityCreated 182829729 2020-10-27 08:17:58.944 16178-16178/com.example.fragmentdemo D/zhangyu1027-RightFragment: onStart 182829729 2020-10-27 08:17:58.944 16178-16178/com.example.fragmentdemo D/zhangyu1027-RightFragment: onResume 182829729 2020-10-27 08:18:01.920 16178-16178/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onAttach 86636105 2020-10-27 08:18:01.920 16178-16178/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onCreate 86636105 2020-10-27 08:18:01.921 16178-16178/com.example.fragmentdemo D/zhangyu1027-RightFragment: onPause 182829729 2020-10-27 08:18:01.921 16178-16178/com.example.fragmentdemo D/zhangyu1027-RightFragment: onStop 182829729 2020-10-27 08:18:01.922 16178-16178/com.example.fragmentdemo D/zhangyu1027-RightFragment: onDestroyView 182829729 2020-10-27 08:18:01.929 16178-16178/com.example.fragmentdemo D/zhangyu1027-RightFragment: onDestroy 182829729 2020-10-27 08:18:01.929 16178-16178/com.example.fragmentdemo D/zhangyu1027-RightFragment: onDetach 182829729 2020-10-27 08:18:01.930 16178-16178/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onCreateView 86636105 2020-10-27 08:18:01.939 16178-16178/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onActivityCreated 86636105 2020-10-27 08:18:01.939 16178-16178/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onStart 86636105 2020-10-27 08:18:01.939 16178-16178/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onResume 86636105

此时点击返回键，整个页面退出：AnotherRightFragment走销毁的生命周期：【onPause -> onStop -> onDestroyView-> onDestroy -> onDetach】

2020-10-27 08:22:05.931 16178-16178/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onPause 86636105 2020-10-27 08:22:06.555 16178-16178/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onStop 86636105 2020-10-27 08:22:06.556 16178-16178/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onDestroyView 86636105 2020-10-27 08:22:06.557 16178-16178/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onDestroy 86636105 2020-10-27 08:22:06.557 16178-16178/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onDetach 86636105 2020-10-27 08:22:06.559 16178-16178/com.example.fragmentdemo D/zhangyu1027: LifeCycleActivity onDestroy127615966

通过replace添加两个Fragment并且添加返回栈

添加代码

private void transactionFragment(Fragment fragment) { //获取FragmentManager FragmentManager fragmentManager = getSupportFragmentManager(); //开启一个事务 FragmentTransaction beginTransaction = fragmentManager.beginTransaction(); //向容器添加或者替换Fragment beginTransaction.replace(R.id.activity_life_cycle_fl, fragment); //beginTransaction.add(R.id.activity_life_cycle_fl, fragment); //加入返回栈 beginTransaction.addToBackStack(null); //提交事务 beginTransaction.commit(); }

先添加两个Fragment， 添加RightFragment，生命周期为：【onAttach -> onCreate -> onCreateView -> onActivityCreated -> onStart -> onResume 】，没有什么疑问，很好理解。 再添加一个AnotherRightFragment，生命周期先为【onAttach -》onCreate 】，跟上一个一样。 不一样的来了，此时RightFragment的生命周期为【onPause -> onStop -> onDestroyView】，没有走【 onDestroy -> onDetach】，因为添加到了返回栈中，RightFragment没有跟当前的Activity解除关联。 然后AnotherRightFragment剩下的生命周期为：【onCreateView -> onActivityCreated -> onStart -> onResume】，这里跟之前一样。

2020-10-27 08:23:40.140 16400-16400/com.example.fragmentdemo D/zhangyu1027: LifeCycleActivity onCreate127615966 2020-10-27 08:23:41.417 16400-16400/com.example.fragmentdemo D/zhangyu1027-RightFragment: onAttach 119552776 2020-10-27 08:23:41.417 16400-16400/com.example.fragmentdemo D/zhangyu1027-RightFragment: onCreate 119552776 2020-10-27 08:23:41.418 16400-16400/com.example.fragmentdemo D/zhangyu1027-RightFragment: onCreateView 119552776 2020-10-27 08:23:41.429 16400-16400/com.example.fragmentdemo D/zhangyu1027-RightFragment: onActivityCreated 119552776 2020-10-27 08:23:41.429 16400-16400/com.example.fragmentdemo D/zhangyu1027-RightFragment: onStart 119552776 2020-10-27 08:23:41.429 16400-16400/com.example.fragmentdemo D/zhangyu1027-RightFragment: onResume 119552776 2020-10-27 08:23:42.088 16400-16400/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onAttach 86636105 2020-10-27 08:23:42.088 16400-16400/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onCreate 86636105 2020-10-27 08:23:42.088 16400-16400/com.example.fragmentdemo D/zhangyu1027-RightFragment: onPause 119552776 2020-10-27 08:23:42.089 16400-16400/com.example.fragmentdemo D/zhangyu1027-RightFragment: onStop 119552776 2020-10-27 08:23:42.090 16400-16400/com.example.fragmentdemo D/zhangyu1027-RightFragment: onDestroyView 119552776 2020-10-27 08:23:42.094 16400-16400/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onCreateView 86636105 2020-10-27 08:23:42.104 16400-16400/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onActivityCreated 86636105 2020-10-27 08:23:42.105 16400-16400/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onStart 86636105 2020-10-27 08:23:42.106 16400-16400/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onResume 86636105

然后点击返回键： 点击第一次：回到上一个Fragment， 栈顶的AnotherRightFragment会销毁，生命周期为：【onPause -> onStop -> onDestroyView-> onDestroy -> onDetach】 RightFragment会重新在展示出来，生命周期为：【onCreateView -> onActivityCreated -> onStart -> onResume 】

2020-10-27 08:28:29.963 16400-16400/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onPause 86636105 2020-10-27 08:28:29.963 16400-16400/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onStop 86636105 2020-10-27 08:28:29.963 16400-16400/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onDestroyView 86636105 2020-10-27 08:28:29.966 16400-16400/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onDestroy 86636105 2020-10-27 08:28:29.966 16400-16400/com.example.fragmentdemo D/zhangyu1027-AnotherRightFragment: onDetach 86636105 2020-10-27 08:28:29.966 16400-16400/com.example.fragmentdemo D/zhangyu1027-RightFragment: onCreateView 119552776 2020-10-27 08:28:29.974 16400-16400/com.example.fragmentdemo D/zhangyu1027-RightFragment: onActivityCreated 119552776 2020-10-27 08:28:29.975 16400-16400/com.example.fragmentdemo D/zhangyu1027-RightFragment: onStart 119552776 2020-10-27 08:28:29.975 16400-16400/com.example.fragmentdemo D/zhangyu1027-RightFragment: onResume 119552776

再点击：此时页面退出。 生命周期为：【onPause -> onStop -> onDestroyView-> onDestroy -> onDetach】

2020-10-27 08:28:59.252 16400-16400/com.example.fragmentdemo D/zhangyu1027-RightFragment: onPause 119552776 2020-10-27 08:28:59.253 16400-16400/com.example.fragmentdemo D/zhangyu1027-RightFragment: onStop 119552776 2020-10-27 08:28:59.253 16400-16400/com.example.fragmentdemo D/zhangyu1027-RightFragment: onDestroyView 119552776 2020-10-27 08:28:59.254 16400-16400/com.example.fragmentdemo D/zhangyu1027-RightFragment: onDestroy 119552776 2020-10-27 08:28:59.254 16400-16400/com.example.fragmentdemo D/zhangyu1027-RightFragment: onDetach 119552776

测试hide和show

private void hide(Fragment fragment) { //获取FragmentManager FragmentManager fragmentManager = getSupportFragmentManager(); //开启一个事务 FragmentTransaction beginTransaction = fragmentManager.beginTransaction(); beginTransaction.hide(fragment); //提交事务 beginTransaction.commit(); } private void show(Fragment fragment) { //获取FragmentManager FragmentManager fragmentManager = getSupportFragmentManager(); //开启一个事务 FragmentTransaction beginTransaction = fragmentManager.beginTransaction(); beginTransaction.show(fragment); //提交事务 beginTransaction.commit(); }

hide和show的时候生命周期无变化