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>

<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>

<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>

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");
    }
}

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;
    }
}

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");
    }
}

运行之后