Fragment生命周期及add、replace、remove、hide&show方法分析

最近做項目時，發現未能完全的了解Fragment的生命周期，以緻在處理邏輯上踩到到了一些坑。是以花了點時間去分析，也順便整理下，下次再碰到Fragment時就可以避免一些坑了（大笑）。

項目有一個Activity類和3個Fragment類。Activity 中放置3個按鈕（實質TextView）可以切換到不同的Fragment上。下面将給出Activity 和Fragment的代碼和layout。

1-1 Fragment1

public class Fragment1 extends Fragment {
    final  String TAG  = " test  Fragment1";

    public Fragment1() {
        // Required empty public constructor
    }

    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        Log.d(TAG,"onAttach");
    }

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.d(TAG,"onCreate");
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment1_layout, null);
        Log.d(TAG,"onCreateView");
        return view;
    }

    @Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        Log.d(TAG,"onActivityCreated");
    }

    @Override
    public void onStart() {
        super.onStart();
        Log.d(TAG,"onStart");
    }

    @Override
    public void onResume() {
        super.onResume();
        Log.d(TAG,"onResume");
    }

    @Override
    public void onPause() {
        super.onPause();
        Log.d(TAG,"onPause");
    }

    @Override
    public void onStop() {
        super.onStop();
        Log.d(TAG,"onStop");
    }

    @Override
    public void onDestroyView() {
        super.onDestroyView();
        Log.d(TAG,"onDestroyView");
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        Log.d(TAG,"onDestroy");
    }

    @Override
    public void onDetach() {
        super.onDetach();
        Log.d(TAG,"onDetach");
    }
}

1-2 fragment1_layout.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:background="#888"
    android:gravity="center">
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="30sp"
        android:text="Fragment1"/>
</LinearLayout>

2-1 Fragment2

public class Fragment2 extends Fragment {
    final  String TAG  = " test  Fragment2";

    public Fragment2() {
        // Required empty public constructor
    }

    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        Log.d(TAG,"onAttach");
    }

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.d(TAG,"onCreate");
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment2_layout, null);
        Log.d(TAG,"onCreateView");
        return view;
    }

    @Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        Log.d(TAG,"onActivityCreated");
    }

    @Override
    public void onStart() {
        super.onStart();
        Log.d(TAG,"onStart");
    }

    @Override
    public void onResume() {
        super.onResume();
        Log.d(TAG,"onResume");
    }

    @Override
    public void onPause() {
        super.onPause();
        Log.d(TAG,"onPause");
    }

    @Override
    public void onStop() {
        super.onStop();
        Log.d(TAG,"onStop");
    }

    @Override
    public void onDestroyView() {
        super.onDestroyView();
        Log.d(TAG,"onDestroyView");
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        Log.d(TAG,"onDestroy");
    }

    @Override
    public void onDetach() {
        super.onDetach();
        Log.d(TAG,"onDetach");
    }
}

2-2 fragment2_layout.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:background="#888"
    android:gravity="center">
<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textSize="30sp"
    android:text="Fragment2"/>
</LinearLayout>

3-1 Fragment3

public class Fragment3 extends Fragment {
    final  String TAG  = " test  Fragment3";

    public Fragment3() {
        // Required empty public constructor
    }

    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        Log.d(TAG,"onAttach");
    }

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.d(TAG,"onCreate");
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment3_layout, null);
        Log.d(TAG,"onCreateView");
        return view;
    }

    @Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        Log.d(TAG,"onActivityCreated");
    }

    @Override
    public void onStart() {
        super.onStart();
        Log.d(TAG,"onStart");
    }

    @Override
    public void onResume() {
        super.onResume();
        Log.d(TAG,"onResume");
    }

    @Override
    public void onPause() {
        super.onPause();
        Log.d(TAG,"onPause");
    }

    @Override
    public void onStop() {
        super.onStop();
        Log.d(TAG,"onStop");
    }

    @Override
    public void onDestroyView() {
        super.onDestroyView();
        Log.d(TAG,"onDestroyView");
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        Log.d(TAG,"onDestroy");
    }

    @Override
    public void onDetach() {
        super.onDetach();
        Log.d(TAG,"onDetach");
    }
}

3-2 fragment3_layout.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:background="#888"
    android:gravity="center">
<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textSize="30sp"
    android:text="Fragment3"/>
</LinearLayout>

4-1 MainActivity

public class MainActivity extends Activity{
    final String TAG = " test  MainActivity";

    TextView mFragment1Tv ;
    TextView mFragment2Tv ;
    TextView mFragment3Tv ;

    FrameLayout mainll ;

    FragmentManager manager ;
    FragmentTransaction transaction;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        this.setContentView(R.layout.activity_main);

        initView();
        initListener();
        initData();

        Log.d(TAG,"onCreate");
    }

    private void initListener() {
        mFragment1Tv.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Fragment1 fragment1= new Fragment1();
                transaction = manager.beginTransaction();
                transaction.add(R.id.main_ll, fragment1,"1");
                transaction.commit();
            }
        });
        mFragment2Tv.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Fragment2 fragment2= new Fragment2();
                transaction = manager.beginTransaction();
                transaction.add(R.id.main_ll, fragment2,"2");
                transaction.commit();
            }
        });
        mFragment3Tv.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Fragment3 fragment3= new Fragment3();
                transaction = manager.beginTransaction();
                transaction.add(R.id.main_ll, fragment3,"3");
                transaction.commit();
            }
        });
    }

    private void initData() {
        manager = getFragmentManager();
    }

    private void initView() {
        mFragment1Tv = (TextView) findViewById(R.id.fragment1_tv);
        mFragment2Tv = (TextView) findViewById(R.id.fragment2_tv);
        mFragment3Tv = (TextView) findViewById(R.id.fragment3_tv);
        mainll  = (FrameLayout) findViewById(R.id.main_ll);

    }

    @Override
    protected void onStart() {
        super.onStart();
        Log.d(TAG,"onCreate");
    }

    @Override
    protected void onRestart() {
        super.onRestart();
        Log.d(TAG,"onRestart");
    }

    @Override
    protected void onResume() {
        super.onResume();
        Log.d(TAG,"onResume");
    }

    @Override
    protected void onPause() {
        super.onPause();
        Log.d(TAG,"onPause");

    }

    @Override
    protected void onStop() {
        super.onStop();
        Log.d(TAG,"onStop");
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        Log.d(TAG,"onDestroy");
    }
}

4-2 activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <LinearLayout
        android:id="@+id/index"
        android:layout_width="match_parent"
        android:layout_height="40dp"
        android:orientation="horizontal">

        <TextView
            android:id="@+id/fragment1_tv"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_margin="5dp"
            android:background="#bbb"
            android:text="Fragment1"
            android:textSize="22sp" />

        <TextView
            android:id="@+id/fragment2_tv"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_margin="5dp"
            android:background="#bbb"
            android:text="Fragment2"
            android:textSize="22sp" />

        <TextView
            android:id="@+id/fragment3_tv"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_margin="5dp"
            android:background="#bbb"
            android:text="Fragment3"
            android:textSize="22sp" />
    </LinearLayout>
    <View
        android:layout_below="@id/index"
        android:layout_width="match_parent"
        android:layout_height="1dp"
        android:background="#aaa"/>

    <LinearLayout
        android:id="@+id/main_ll"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        android:layout_alignParentBottom="true"
        android:layout_alignParentStart="true">
    </LinearLayout>


</RelativeLayout>

5 測試生命周期

(一) add 方法分析

1.啟動app，log如圖：

Fragment生命周期及add、replace、remove、hide&show方法分析

界面如下：

Fragment生命周期及add、replace、remove、hide&show方法分析

2.點選Fragment1，log如下:

Fragment生命周期及add、replace、remove、hide&show方法分析

界面如下：

Fragment生命周期及add、replace、remove、hide&show方法分析

3點選fragment2 log如下： (這裡并沒有觸發fragment1的生命周期)

Fragment生命周期及add、replace、remove、hide&show方法分析

界面如下：

Fragment生命周期及add、replace、remove、hide&show方法分析

4點選fragment3 log如下：

Fragment生命周期及add、replace、remove、hide&show方法分析

界面如下：

Fragment生命周期及add、replace、remove、hide&show方法分析

5 在此時分為兩次不同的操作：

5-1 測試傳回

操作：點選傳回鍵，此時應用已經退出。log如下：

Fragment生命周期及add、replace、remove、hide&show方法分析

5-2 home鍵測試

操作：（1）點選home鍵，app退到背景，log如下:

Fragment生命周期及add、replace、remove、hide&show方法分析

（2）點選應用圖示重新打開app，log如下:

Fragment生命周期及add、replace、remove、hide&show方法分析

6 回退棧測試

再回到5-1 ，如果想要點選傳回鍵回到上一個Fragment的話，那麼就需要加入到會退棧。

修改 MainActivity 的方法initListener如下：

private void initListener() {
        mFragment1Tv.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Fragment1 fragment1= new Fragment1();
                transaction = manager.beginTransaction();
                transaction.add(R.id.main_ll, fragment1,"1");
                transaction.addToBackStack(null);
                transaction.commit();
            }
        });
        mFragment2Tv.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Fragment2 fragment2= new Fragment2();
                transaction = manager.beginTransaction();
                transaction.add(R.id.main_ll, fragment2,"2");
                transaction.addToBackStack(null);
                transaction.commit();
            }
        });
        mFragment3Tv.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Fragment3 fragment3= new Fragment3();
                transaction = manager.beginTransaction();
                transaction.add(R.id.main_ll, fragment3,"3");
                transaction.addToBackStack(null);
                transaction.commit();

            }
        });
    }

操作：執行 1.打開app,2.點選Fragment，3.點選Fragment2，4.點選Fragment3。

此時清空LogCat，再點選傳回鍵Log如下：

Fragment生命周期及add、replace、remove、hide&show方法分析

此時界面回到Fragment2，而其他Fragment和Activity的生命周期是沒有變化的。若再點選傳回鍵将回到Fragment1界面，再點選傳回鍵就是回到Activity界面了。

(二) replace方法分析

修改 MainActivity 的方法initListener如下：（主要是替換add為replace）

private void initListener() {
        mFragment1Tv.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Fragment1 fragment1= new Fragment1();
                transaction = manager.beginTransaction();
                transaction.replace(R.id.main_ll, fragment1,"1");
               //transaction.add(R.id.main_ll, fragment1,"1");
             // transaction.addToBackStack(null);
                transaction.commit();
            }
        });
        mFragment2Tv.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Fragment2 fragment2= new Fragment2();
                transaction = manager.beginTransaction();
                transaction.replace(R.id.main_ll, fragment2,"2");
                //transaction.add(R.id.main_ll, fragment2,"2");
              // transaction.addToBackStack(null);
                transaction.commit();
            }
        });
        mFragment3Tv.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Fragment3 fragment3= new Fragment3();
                transaction = manager.beginTransaction();
                transaction.replace(R.id.main_ll, fragment3,"3");
                //transaction.add(R.id.main_ll, fragment3,"3");
                //transaction.addToBackStack(null);
                transaction.commit();

            }
        });
    }

1.測試replace

操作：啟動app，然後點選Fragment1，再點選Fragment2，log如下：

Fragment生命周期及add、replace、remove、hide&show方法分析

2.測試傳回鍵

在上一步驟的基礎上點選實體傳回鍵Log如下：（應用程式已經退出了）

Fragment生命周期及add、replace、remove、hide&show方法分析

3.在（二）1的基礎上點選home鍵，再重新打開app，log如下:

Fragment生命周期及add、replace、remove、hide&show方法分析

4．此時看下會退棧的情況。

修改 MainActivity 的方法initListener，主要是取消

的注釋。

操作：打開app，點選Fragment1，點選Fragment2，清空logCat，再點選傳回鍵，此時log如下：

Fragment生命周期及add、replace、remove、hide&show方法分析

可見replace 是會銷毀掉被replace 的Fragment。

(三) hide &show方法分析。

修改 MainActivity如下：（在activity的oncreate中add Fragment1和Fragment2，修改mFragment2Tv的點選事件。）

public class MainActivity extends Activity{
    final String TAG = "testFragment  MainActivity";

    TextView mFragment1Tv ;
    TextView mFragment2Tv ;
    TextView mFragment3Tv ;

    FrameLayout mainll ;

    FragmentManager manager ;
    FragmentTransaction transaction;

    Fragment1 fragment1;
    Fragment2 fragment2;
    Fragment3 fragment3;



    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        this.setContentView(R.layout.activity_main);

        initView();
        initListener();
        initData();

        Log.d(TAG,"onCreate");
    }

    private void initListener() {
        mFragment1Tv.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                transaction = manager.beginTransaction();
                transaction.add(R.id.main_ll, fragment1,"1");
                transaction.commit();
            }
        });
        mFragment2Tv.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                transaction = manager.beginTransaction();
                transaction.hide(fragment1).show(fragment2);
                transaction.commit();
            }
        });
        mFragment3Tv.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                transaction = manager.beginTransaction();
                transaction.replace(R.id.main_ll, fragment3,"3");
//                transaction.add(R.id.main_ll, fragment3,"3");
                transaction.addToBackStack(null);
                transaction.commit();

            }
        });
    }

    private void initData() {
        manager = getFragmentManager();
        fragment1= new Fragment1();
        fragment2= new Fragment2();
        fragment3= new Fragment3();
        transaction = manager.beginTransaction();
        transaction.add(R.id.main_ll, fragment2,"2");
        transaction.add(R.id.main_ll, fragment1,"1");
        transaction.commit();
    }

    private void initView() {
        mFragment1Tv = (TextView) findViewById(R.id.fragment1_tv);
        mFragment2Tv = (TextView) findViewById(R.id.fragment2_tv);
        mFragment3Tv = (TextView) findViewById(R.id.fragment3_tv);
        mainll  = (FrameLayout) findViewById(R.id.main_ll);

    }

    @Override
    protected void onStart() {
        super.onStart();
        Log.d(TAG,"onStart");
    }

    @Override
    protected void onRestart() {
        super.onRestart();
        Log.d(TAG,"onRestart");
    }

    @Override
    protected void onResume() {
        super.onResume();
        Log.d(TAG,"onResume");
    }

    @Override
    protected void onPause() {
        super.onPause();
        Log.d(TAG,"onPause");

    }

    @Override
    protected void onStop() {
        super.onStop();
        Log.d(TAG,"onStop");
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        Log.d(TAG,"onDestroy");
    }
}

操作：啟動app ，log如下圖，代碼裡面是先add Fragment2 再add Fragment1，此時顯示的界面是Fragment1 的界面，然後點選TextView mFragment2Tv，界面切換到了Fragment2上，而log無任何的資訊列印，可見hide &show 方法不觸發Fragment生命周期，隻影響它的顯示。

Fragment生命周期及add、replace、remove、hide&show方法分析

(四) remove方法分析

在 (三)hide&show方法分析的代碼基礎上修改MainActivity 如下：

(其他代碼不變，隻修改為remove方法)

mFragment2Tv.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                transaction = manager.beginTransaction();
                transaction.remove(fragment1).show(fragment2);
                transaction.commit();
            }
        });

啟動app 時的log:

Fragment生命周期及add、replace、remove、hide&show方法分析

此時點選Fragment2，log如下:

Fragment生命周期及add、replace、remove、hide&show方法分析

本以為分析下Fragment會很簡單，想不到分析Fragment+一篇文章能耗那麼多時間，看來得加個鹵蛋犒勞犒勞自己了（偷笑中…）

Fragment生命周期及add、replace、remove、hide&show方法分析

繼續閱讀

專訪鄧凡平：深入了解Android

與專家面對面：Android開發入門問與答

Android MVP架構MVCMVP

mvp初探

Android常用工具類簡介目錄

android常用工具類轉載自：http://www.trinea.cn/android/android-common-utils/Android常用工具類

Android常用工具類ToastUtilsSizeUtilsLogUtilsRetrofitManagerAnimUtil

Android Studio 0.8.0解決 Failure [INSTALL_FAILED_OLDER_SDK] 問題

Android – ListView 中添加按鈕，動态删除添加ItemView的操作

Kotlin的ListView與RecyclerView的簡單應用

關于公司的那些坑：Android Studio篇

android SQLite事務和kotlin協程

無法正常編譯錯誤Compilation failed to complete

關于Gradle配置的小結

AOP程式設計_Android優雅權限架構(1)概念基礎，2021金三銀四前言正文大綱正文

Android APK檔案反編譯Android APK檔案反編譯

Fragment生命周期及add、replace、remove、hide&amp;show方法分析

繼續閱讀

Fragment生命周期及add、replace、remove、hide&show方法分析