Android Fragmnet 两种添加方式的区别及所涉及的生命周期

电玩女神 2021-11-09 09:46 263阅读 0赞

一、Demo所涉及的部分代码

1.MainActivity的布局文件

<?xml version="1.0" encoding="utf-8"?>
    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:orientation="vertical"
        android:background="#ffffff"
        android:layout_width="match_parent"
        android:layout_height="match_parent">
    
        <FrameLayout
            android:id="@+id/main_frame_layout"
            android:background="#dddddd"
            android:layout_weight="1"
            android:layout_width="match_parent"
            android:layout_height="0dp">
        </FrameLayout>
    
        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="48dp">
            <Button
                android:id="@+id/btn1"
                android:layout_weight="1"
                android:layout_width="0dp"
                android:layout_height="match_parent"
                android:background="#ffffff"
                android:text="首页"/>
            <Button
                android:id="@+id/btn2"
                android:layout_weight="1"
                android:layout_width="0dp"
                android:layout_height="match_parent"
                android:background="#ffffff"
                android:text="消息"/>
        </LinearLayout>
    </LinearLayout>

MainActivity的代码：

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
        private static final String TAG = "MainActivity";
        private FrameLayout main_frame_layout;
        private Button btn1;
        private Button btn2;
        private Button btn3;
        FragmentA f1;
        FragmentB f2;
        FragmentC f3;
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            main_frame_layout = findViewById(R.id.main_frame_layout);
            btn1 = findViewById(R.id.btn1);
            btn2 = findViewById(R.id.btn2);
            btn3 = findViewById(R.id.btn3);
            btn1.setOnClickListener(this);
            btn2.setOnClickListener(this);
            btn3.setOnClickListener(this);
            initFragment1();
    
            Log.i(TAG, "onCreate()");
    
        }
    
        @Override
        protected void onStart() {
            super.onStart();
            Log.i(TAG, "onStart()");
        }
    
        @Override
        protected void onResume() {
            super.onResume();
            Log.i(TAG, "onResume()");
        }
    
        @Override
        protected void onPause() {
            super.onPause();
            Log.i(TAG, "onPause()");
        }
    
        @Override
        protected void onStop() {
            super.onStop();
            Log.i(TAG, "onStop()");
        }
    
        @Override
        protected void onDestroy() {
            super.onDestroy();
            Log.i(TAG, "onDestroy()");
        }
    
    
        private void initFragment1() {
            FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
            //第一种方式使用add
            if (f1 == null) {
                f1 = new FragmentA("首页");
                transaction.add(R.id.main_frame_layout, f1);
            }
            //隐藏
            hideFragment(transaction);
            //展示
            transaction.show(f1);
    
    //        //第二种方式  replace
    //        if(f1==null){
    //            f1=new FragmentA("首页");
    //        }
    //        transaction.replace(R.id.main_frame_layout,f1);
    //        transaction.commit();
        }
    
        private void hideFragment(FragmentTransaction transaction) {
            if (f1 != null) {
                transaction.hide(f1);
            }
            if (f2 != null) {
                transaction.hide(f2);
            }
            if (f3 != null) {
                transaction.hide(f3);
            }
        }
    
        public void initFragment2() {
            FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
            //第一种方式使用add
            if (f2 == null) {
                f2 = new FragmentB("消息");
                transaction.add(R.id.main_frame_layout, f2);
            }
            //隐藏
            hideFragment(transaction);
            //展示
            transaction.show(f2);
    
    //        //第二种方式  replace
    //        if (f2 == null) {
    //            f2 = new FragmentB("消息");
    //        }
    //        transaction.replace(R.id.main_frame_layout, f2);
    //
    //        transaction.commit();
        }
    
        @Override
        public void onClick(View view) {
            if (view == btn1) {
                initFragment1();
            } else if (view == btn2) {
                initFragment2();
            } else if (view == btn3) {
                initFragment3();
            }
        }
    
        private void initFragment3() {
            FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
            //第一种方式使用add
            if (f3 == null) {
                f3 = new FragmentC("消息");
                transaction.add(R.id.main_frame_layout, f3);
            }
            //隐藏
            hideFragment(transaction);
            //展示
            transaction.show(f3);
    
    
    //        //第二种方式  replace
    //        if (f3 == null) {
    //            f3 = new FragmentC("消息");
    //        }
    //        transaction.replace(R.id.main_frame_layout, f3);
            //transaction.commit();
        }
    }

FragmentA:

public class FragmentA extends Fragment {
        private static  final String TAG="FragmentA";
        private TextView tv;
        private String name;
        public FragmentA(String fName){
            this.name = fName;
        }
    
        @Override
        public void onAttach(Context context) {
            super.onAttach(context);
            Log.i(TAG,"onAttach()");
        }
    
        @Override
        public void onCreate(@Nullable Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            Log.i(TAG,"onCreate()");
        }
    
        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
            View view = LayoutInflater.from(getActivity()).inflate(R.layout.fragment_,container,false);
            tv = (TextView) view.findViewById(R.id.fragment_tv);
            tv.setText(name);
            tv.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    tv.setText("我变了-" + name);
                }
            });
            Log.i(TAG,"onCreatedView()");
            return view;
        }
    
        @Override
        public void onActivityCreated(@Nullable Bundle savedInstanceState) {
            super.onActivityCreated(savedInstanceState);
            Log.i(TAG,"onActivityCreated()");
        }
    
        @Override
        public void onPause() {
            super.onPause();
            Log.i(TAG,"onPause()");
        }
    
        @Override
        public void onStop() {
            super.onStop();
            Log.i(TAG,"onStop()");
        }
    
        @Override
        public void onDestroyView() {
            super.onDestroyView();
            Log.i(TAG,"onDestroyView()");
        }
    
        @Override
        public void onDetach() {
            super.onDetach();
            Log.i(TAG,"onDettach()");
        }
    
        @Override
        public void onDestroy() {
            super.onDestroy();
            Log.i(TAG,"onDestroy()");
        }
    }

FragmentA对应的布局文件：

<?xml version="1.0" encoding="utf-8"?>
    <RelativeLayout 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:background="#dddddd">
    
        <TextView
            android:id="@+id/fragment_tv"
            android:layout_centerInParent="true"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="fragment"
            android:textColor="#000000"/>
    
    </RelativeLayout>

FragmnetB、FragmentC与FragmentA的代码是一样的

二、使用add、hide、show的方式添加Fragment

1、程序一运行，首先加载的FragmentA对应的界面此时所涉及的生命周期方法是：

MainActivity: onCreate()  
FragmentA: onAttach()  
FragmentA: onCreate()  
FragmentA: onCreatedView()  
FragmentA: onActivityCreated()  
MainActivity: onStart()  
MainActivity: onResume()

2、此时切换到FragmnetB所涉及的生命周期方法有：

FragmentB: onAttach()  
FragmentB: onCreate()  
FragmentB: onCreatedView()  
FragmentB: onActivityCreated()

3、在切换回FraagmentA

2019-08-02 20:04:16.874 25640-25640/com.example.testfragment I/ViewRootImpl: jank\_removeInvalidNode all the node in jank list is out of time

4、然后在点击Home键后执行的生命周期方法

FragmentA: onPause()  
FragmentB: onPause()  
MainActivity: onPause()  
FragmentA: onStop()  
FragmentB: onStop()  
MainActivity: onStop()

5、点击桌面应用图标在进去当前应用：

MainActivity: onStart()  
MainActivity: onResume()

6、点击返回键退出应用

FragmentA: onPause()  
FragmentB: onPause()  
MainActivity: onPause()  
FragmentA: onStop()  
FragmentB: onStop()  
MainActivity: onStop()  
FragmentA: onDestroyView()  
FragmentA: onDestroy()  
FragmentA: onDettach()  
FragmentB: onDestroyView()  
FragmentB: onDestroy()  
FragmentB: onDettach()  
MainActivity: onDestroy()

三、使用replace方式替换

1、第一次启动程序

MainActivity: onCreate()  
FragmentA: onAttach()  
FragmentA: onCreate()  
FragmentA: onCreatedView()  
FragmentA: onActivityCreated()  
MainActivity: onStart()  
MainActivity: onResume()

2、切换至FragmentB

FragmentB: onAttach()  
FragmentB: onCreate()  
FragmentA: onPause()  
FragmentA: onStop()  
FragmentA: onDestroyView()  
FragmentA: onDestroy()  
FragmentA: onDettach()  
FragmentB: onCreatedView()  
FragmentB: onActivityCreated()

3、切换至FragmentC

FragmentC: onAttach()  
FragmentC: onCreate()  
FragmentB: onPause()  
FragmentB: onStop()  
FragmentB: onDestroyView()  
FragmentB: onDestroy()  
FragmentB: onDettach()  
FragmentC: onCreatedView()  
FragmentC: onActivityCreated()

4、此时按Home键

FragmentC: onPause()  
MainActivity: onPause()  
FragmentC: onStop()  
MainActivity: onStop()

5、在按图标重新启动应用程序

MainActivity: onStart()  
MainActivity: onResume()

6、此时在按返回键

FragmentA: onPause()  
MainActivity: onPause()

FragmentA: onStop()  
MainActivity: onStop()  
FragmentA: onDestroyView()  
FragmentA: onDestroy()  
FragmentA: onDettach()  
MainActivity: onDestroy()

四、add方式和replace方式的区别

add、hide、show方式添加Fragmnet，再次切换回来时不会重新创建该Fragment的实例~  直接复用

replace方式添加的Fragment，再次切换回来时会重新创建Fragment的实例，每切换一次创建一次~

五、点击Home键返回桌面，在想让应用重新启动的方式有？

①点击应用图标

②多任务中点击启动

③也有可能是，系统内存不足了，此时应用被杀死了，在被重新启动