【Android】Activity与Fragment的生命周期的关系

小灰灰 2022-08-17 14:10 41阅读 0赞

**一、问题描述：**

> 假设有两个Activity（1和2）,每个Activity拥有一个Fragment，并分别有一个Button，点击Button1可以start Activity2，然后点击Button2可以finish掉自己（即Activity2）,然后返回到Activity1。根据这个简单模型描述一下Activity和Fragment的生命周期之间的依赖关系？

![这里写图片描述][20151125142250638]

--------------------

**二、生命周期知识**

Activity和Fragment的生命周期图谱可以参考我的另外一篇博客：[**【Android】Fragment的生命周期详解**][Android_Fragment]，他们的关系大致如下图：

![这里写图片描述][20151125114550996]

--------------------

**三、代码验证**

MainActivity和SecondActivity的布局是这样的，里面各添加了一个Fragment：

![这里写图片描述][20160122171224773] ![这里写图片描述][20160122171401607]

/**
      * MainActivity布局xml文件
      */
    
    <?xml version="1.0" encoding="utf-8"?>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:orientation="vertical" android:layout_width="fill_parent"
        android:layout_height="fill_parent">
    
        <Button
            android:id="@+id/button"
            android:text="开启第二个Activity"
            android:layout_gravity="center"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"></Button>
    
        <LinearLayout
            android:id="@+id/linearlayout"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="vertical"
            android:background="#339999">
        </LinearLayout>
    
    </LinearLayout>

/**
      * MainActivity.java代码，SecondActivity的代码与之类似，这里就不贴那么多了
      */
    public class MainActivity extends Activity {
        
        private static final String LOG_TAG = "MainActivity";
        private Button mButton;
    
        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            Log.w(LOG_TAG, "==============onCreate()");
    
            FragmentManager fragmentManager = getFragmentManager();
            FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
    
            FirstFragment firstFragment = new FirstFragment();
            fragmentTransaction.add(R.id.linearlayout, firstFragment);
            fragmentTransaction.commit();
    
            mButton = (Button) findViewById(R.id.button);
            mButton.setOnClickListener(new View.OnClickListener() {
    
                @Override
                public void onClick(View v) {
                    Log.w(LOG_TAG, "------------------mButton onClick-------------------");
                    startActivity(new Intent(MainActivity.this, SecondActivity.class));
                }
            });
        }
    
        @Override
        protected void onStart() {
            super.onStart();
            Log.w(LOG_TAG, "==============onStart()");
        }
    
        @Override
        protected void onRestart() {
            super.onRestart();
            Log.w(LOG_TAG, "==============onRestart()");
        }
    
        @Override
        protected void onResume() {
            super.onResume();
            Log.w(LOG_TAG, "==============onResume()");
        }
    
        @Override
        protected void onPause() {
            super.onPause();
            Log.w(LOG_TAG, "==============onPause()");
        }
    
        @Override
        protected void onStop() {
            super.onStop();
            Log.w(LOG_TAG, "==============onStop()");
        }
    
        @Override
        protected void onDestroy() {
            super.onDestroy();
            Log.w(LOG_TAG, "==============onDestroy()");
        }
    }

/**
      * FirstFragment.java代码， SecondFragment和它差不多一样
      */
    public class FirstFragment extends Fragment {
        
        private static final String LOG_TAG = "FirstFragment";
        private static final String ARG_PARAM1 = "param1";
        private static final String ARG_PARAM2 = "param2";
    
        private String mParam1;
        private String mParam2;
    
        public FirstFragment() {
        }
    
        @Override
        public void onAttach(Activity activity) {
            super.onAttach(activity);
            Log.w(LOG_TAG, "onAttach...");
        }
    
        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            Log.w(LOG_TAG, "onCreate...");
            if (getArguments() != null) {
                mParam1 = getArguments().getString(ARG_PARAM1);
                mParam2 = getArguments().getString(ARG_PARAM2);
            }
        }
    
        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {
            Log.w(LOG_TAG, "onCreateView...");
            return inflater.inflate(R.layout.fragment_first, container, false);
        }
    
    
        @Override
        public void onActivityCreated(Bundle savedInstanceState) {
            super.onActivityCreated(savedInstanceState);
            Log.w(LOG_TAG, "onActivityCreated...");
        }
    
        @Override
        public void onStart() {
            super.onStart();
            Log.w(LOG_TAG, "onStart...");
        }
    
    
        @Override
        public void onResume() {
            super.onResume();
            Log.w(LOG_TAG, "onResume...");
        }
    
        @Override
        public void onPause() {
            super.onPause();
            Log.w(LOG_TAG, "onPause...");
        }
    
        @Override
        public void onStop() {
            super.onStop();
            Log.w(LOG_TAG, "onStop...");
        }
    
        @Override
        public void onDestroyView() {
            super.onDestroyView();
            Log.w(LOG_TAG, "onDestroyView...");
        }
    
        @Override
        public void onDestroy() {
            super.onDestroy();
            Log.w(LOG_TAG, "onDestroy...");
        }
    
        @Override
        public void onDetach() {
            super.onDetach();
            Log.w(LOG_TAG, "onDetach...");
        }
    
    }

--------------------

**四、运行结果**

1、第一次打开以后：

com.example.kuguan.anlearning W/MainActivity﹕ ==============onCreate()
    com.example.kuguan.anlearning W/FirstFragment﹕ onAttach...
    com.example.kuguan.anlearning W/FirstFragment﹕ onCreate...
    com.example.kuguan.anlearning W/FirstFragment﹕ onCreateView...
    com.example.kuguan.anlearning W/FirstFragment﹕ onActivityCreated...
    com.example.kuguan.anlearning W/MainActivity﹕ ==============onStart()
    com.example.kuguan.anlearning W/FirstFragment﹕ onStart...
    com.example.kuguan.anlearning W/MainActivity﹕ ==============onResume()
    com.example.kuguan.anlearning W/FirstFragment﹕ onResume...

2、点击MainActivity中的按钮“打开第二个Activity”以后：

com.example.kuguan.anlearning W/MainActivity﹕ ----------------mButton onClick-----------------
    com.example.kuguan.anlearning W/FirstFragment﹕ onPause...
    com.example.kuguan.anlearning W/MainActivity﹕ ==============onPause()
    com.example.kuguan.anlearning W/SecondFragment﹕ onAttach...
    com.example.kuguan.anlearning W/SecondFragment﹕ onCreate...
    com.example.kuguan.anlearning W/SecondFragment﹕ onCreateView...
    com.example.kuguan.anlearning W/SecondFragment﹕ onActivityCreated...
    com.example.kuguan.anlearning W/SecondActivity﹕ ==============onStart()
    com.example.kuguan.anlearning W/SecondFragment﹕ onStart...
    com.example.kuguan.anlearning W/SecondActivity﹕ ==============onResume()
    com.example.kuguan.anlearning W/SecondFragment﹕ onResume...
    com.example.kuguan.anlearning W/FirstFragment﹕ onStop...
    com.example.kuguan.anlearning W/MainActivity﹕ ==============onStop()

3、点击SecondActivity的按钮“finish”之后：

com.example.kuguan.anlearning W/SecondActivity﹕ -----------------mButton onClick------------------
    com.example.kuguan.anlearning W/SecondFragment﹕ onPause...
    com.example.kuguan.anlearning W/SecondActivity﹕ ==============onPause()
    com.example.kuguan.anlearning W/MainActivity﹕ ==============onRestart()
    com.example.kuguan.anlearning W/MainActivity﹕ ==============onStart()
    com.example.kuguan.anlearning W/FirstFragment﹕ onStart...
    com.example.kuguan.anlearning W/MainActivity﹕ ==============onResume()
    com.example.kuguan.anlearning W/FirstFragment﹕ onResume...
    com.example.kuguan.anlearning W/SecondFragment﹕ onStop...
    com.example.kuguan.anlearning W/SecondActivity﹕ ==============onStop()
    com.example.kuguan.anlearning W/SecondFragment﹕ onDestroyView...
    com.example.kuguan.anlearning W/SecondFragment﹕ onDestroy...
    com.example.kuguan.anlearning W/SecondFragment﹕ onDetach...
    com.example.kuguan.anlearning W/SecondActivity﹕ ==============onDestroy()

4、点击back键使MainActivity退到后台：

com.example.kuguan.anlearning W/FirstFragment﹕ onPause...
    com.example.kuguan.anlearning W/MainActivity﹕ ==============onPause()
    com.example.kuguan.anlearning W/FirstFragment﹕ onStop...
    com.example.kuguan.anlearning W/MainActivity﹕ ==============onStop()
    com.example.kuguan.anlearning W/FirstFragment﹕ onDestroyView...
    com.example.kuguan.anlearning W/FirstFragment﹕ onDestroy...
    com.example.kuguan.anlearning W/FirstFragment﹕ onDetach...
    com.example.kuguan.anlearning W/MainActivity﹕ ==============onDestroy()

5、在MianActivity显示的时候，按HOME键：

6、然后再点击Icon打开：

com.example.kuguan.anlearning W/MainActivity﹕ ==============onRestart()
    com.example.kuguan.anlearning W/MainActivity﹕ ==============onStart()
    com.example.kuguan.anlearning W/FirstFragment﹕ onStart...
    com.example.kuguan.anlearning W/MainActivity﹕ ==============onResume()
    com.example.kuguan.anlearning W/FirstFragment﹕ onResume...

【参考资料】：  
1、[Fragment和Activity][Fragment_Activity]

[20151125142250638]: /images/20220731/ca9cdfc2989d402285377cae3d0f76a9.png
[Android_Fragment]: http://blog.csdn.net/u010983881/article/details/50034805
[20151125114550996]: /images/20220731/c3849c57891d47b787a68cc02774d256.png
[20160122171224773]: https://img-blog.csdn.net/20160122171224773
[20160122171401607]: /images/20220731/3f1d72323dfe48749c0138c4a68511a5.png
[Fragment_Activity]: http://www.cnblogs.com/mengdd/archive/2013/01/11/2856374.html