Android Fragment生命周期及静态加载

一个Fragment必须总是被嵌入到一个Activity中,它的生命周期直接被其所属的宿主Activity生命周期影响,它的状态会随宿主的状态变化而变化。

要创建一个Fragment 必须创建一个Fragment的子类,或者继承自另一个已经存在的Fragment的子类.并重写onCreateView()方法加载UI。

静态加载两个Fragment，左边显示三个Button,右边显示一个TextView

 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools"
     android:id="@+id/activity_main"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:orientation="vertical"
     tools:context="com.example.lesson10_fragment.MainActivity">

     <fragment
         android:tag="fragment1"
         android:name="com.example.lesson10_fragment.Fragment1"
         android:layout_width="match_parent"
         android:layout_height="wrap_content" />

     <fragment
         android:tag="fragment2"
         android:name="com.example.lesson10_fragment.Fragment2"
         android:layout_width="match_parent"
         android:layout_height="wrap_content" />

 </LinearLayout>

activity_main.xml

 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:orientation="vertical">

     <Button
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:text="Button1"/>
     <Button
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:text="Button2"/>
     <Button
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:text="Button3"/>
 </LinearLayout>

frag1_layout.xml

 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
     android:layout_height="match_parent">

     <TextView
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:text="哈哈哈啊哈哈"
         android:textSize="50sp"
         android:layout_centerInParent="true"/>

 </RelativeLayout>

frag2_layout.xml

 public class Fragment1 extends Fragment{

     @Override
     public void onAttach(Context context) {
         super.onAttach(context);
         Log.e("TAG","----------Fragment1----onAttach");
     }

     @Override
     public void onCreate(@Nullable Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         Log.e("TAG","----------Fragment1----onCreate");
     }

     @Nullable
     @Override
     public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
         View layout = View.inflate(getActivity(),R.layout.frag1_layout,null);
         //由于这super.onCreateView(inflater, container, savedInstanceState)返回的是null,所以不能用

         Log.e("TAG","----------Fragment1----onCreateView");
         return layout;
     }

     @Override
     public void onActivityCreated(@Nullable Bundle savedInstanceState) {
         super.onActivityCreated(savedInstanceState);
         Log.e("TAG","----------Fragment1----onActivityCreated");
     }

     @Override
     public void onStart() {
         super.onStart();
         Log.e("TAG","----------Fragment1----onStart");
     }

     @Override
     public void onResume() {
         super.onResume();
         Log.e("TAG","----------Fragment1----onResume");
     }

     @Override
     public void onPause() {
         super.onPause();
         Log.e("TAG","----------Fragment1----onPause");
     }

     @Override
     public void onStop() {
         super.onStop();
         Log.e("TAG","----------Fragment1----onStop");
     }

     @Override
     public void onDestroyView() {
         super.onDestroyView();
         Log.e("TAG","----------Fragment1----onDestroyView");
     }

     @Override
     public void onDestroy() {
         super.onDestroy();
         Log.e("TAG","----------Fragment1----onDestroy");
     }

     @Override
     public void onDetach() {
         super.onDetach();
         Log.e("TAG","----------Fragment1----onDetach");
     }
 }

Fragment1.java

 public class Fragment2 extends Fragment{

     @Nullable
     @Override
     public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
         View layout = View.inflate(getActivity(),R.layout.frag2_layout,null);
         return layout;
     }
 }

Fragment2.java

 public class MainActivity extends AppCompatActivity {

     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
         Log.e("TAG","---MainActivity----onCreate");
     }

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

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

     @Override
     protected void onPause() {
         super.onPause();
         Log.e("TAG","---MainActivity----onPause");
     }

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

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

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

MainActivity.java

运行之后