UI进阶 | Notion

（1）Fragment

允许将Activity拆分成多个完全独立封装的可重用组件

**Fragment依附于Activity ，不独立存在，
一个Activity中可以包含多个Fragment，一个Fragment可以被包含在多个Activity中**

创建Fragment时，需要实现

onCreate()
onCreateView()
onPause()

将Fragment加载到Activity中主要有两种方式：

静态加载：将Fragment加载到布局文件中

动态加载：在Activity代码中动态添加Fragment

讲台加载Fragment的步骤：
  1. 生成Fragment类文件： 在java 中 new  fragment  选择 Blank Fragment
  2. 把新城生成的Fragment类中没用的内容删掉
  3.把Fragment 加载到Activity中：
      <fragment
            android:id="@+id/fragment1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:name="com.example.chapter4ruanyi.fragment.QianrushiFragment">
        </fragment>
    注意1：添加 android:name属性，值是生成的Fragment类
   注意2：必须 添加 android:id属性

动态加载方式：
   1. 生成Fragment类文件： 在java 中 new  fragment  选择 Blank Fragment
   2. 把新城生成的Fragment类中没用的内容删掉
   3. 在Activity 的布局文件中，添加出发动作，比如 按钮
   4. 添加按钮的绑定函数
   5. 在绑定函数中添加Fragment：
       ① 获取Fragment管理器：FragmentManager fragmentManager = getSupportFragmentManager();
      ② 获取 事务：FragmentTransaction  fragmentTransaction=  fragmentManager.beginTransaction();
     ③ 创建Fragment对象
    ④ 把创建的对象添加到事务中
   ⑤ 对事物进行提交

动态删除Fragment步骤：
  ① 获取Fragment管理器：FragmentManager fragmentManager = getSupportFragmentManager();
  ② 获取 事务：FragmentTransaction  fragmentTransaction=  fragmentManager.beginTransaction();
  ③ 获取要删除的fragment :fragmentManager.findFragmentByTag("abc");
  ④ 调用删除方法：fragmentTransaction.remove(fg);
  ⑤ 对事物进行提交

替换Fragment的步骤：
  ① 获取Fragment管理器：FragmentManager fragmentManager = getSupportFragmentManager();
  ② 获取 事务：FragmentTransaction  fragmentTransaction=  fragmentManager.beginTransaction();
  ③ 生成新的Fragmengt对象
  ④ 调用替换方法：fragmentTransaction.replace(R.id.frameMid,qfg2);
  ⑤ 对事物进行提交

代码：

=====================================================================================

---------------------------activity_main_qianrushi.java----------------
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="<http://schemas.android.com/apk/res/android>"
    xmlns:app="<http://schemas.android.com/apk/res-auto>"
    xmlns:tools="<http://schemas.android.com/tools>"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal"
    tools:context=".MainActivityQianrushi">

    <LinearLayout
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="1"
        android:orientation="vertical">

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="左Frame"></TextView>

        <Button
            android:id="@+id/btadd"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="add"
            android:onClick="add">
        </Button>

        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="remove"
            android:onClick="remove">
        </Button>

        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="change"
            android:onClick="change">
        </Button>
    </LinearLayout>

    <LinearLayout
        android:id="@+id/frameMid"
        android:layout_width="0dp"
        android:layout_weight="2"
        android:layout_height="match_parent"
        android:orientation="vertical">

    </LinearLayout>

    <LinearLayout
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_weight="2"
        android:orientation="vertical">

        <fragment
            android:id="@+id/fragment1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:name="com.example.chapter4ruanyi.fragment.QianrushiFragment">

        </fragment>

    </LinearLayout>

</LinearLayout>
-----------------------------MainActivityQianrushi .java----------------------------------------
public class MainActivityQianrushi extends AppCompatActivity {

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

    public void add(View v){
        FragmentManager fragmentManager = getSupportFragmentManager();
        FragmentTransaction  fragmentTransaction=  fragmentManager.beginTransaction();

        QianrushiFragment qianrushiFragment = new QianrushiFragment();
        QianrushiFragment2 qianrushiFragment2 = new QianrushiFragment2();

        fragmentTransaction.add(R.id.frameMid,qianrushiFragment,"abc");
        fragmentTransaction.add(R.id.frameMid,qianrushiFragment2,"abc");

        fragmentTransaction.addToBackStack("aaa");
        fragmentTransaction.commit();

    }

    public void remove(View v){
        FragmentManager fragmentManager = getSupportFragmentManager();
        FragmentTransaction  fragmentTransaction=  fragmentManager.beginTransaction();
        Fragment fg = fragmentManager.findFragmentByTag("abc");
        fragmentTransaction.remove(fg);
        fragmentTransaction.commit();
    }

    public void change(View v){
        QianrushiFragment2 qfg2 = new QianrushiFragment2();
        FragmentManager fragmentManager = getSupportFragmentManager();
        FragmentTransaction  fragmentTransaction=  fragmentManager.beginTransaction();
        fragmentTransaction.replace(R.id.frameMid,qfg2);
        fragmentTransaction.commit();
    }
}
-------------------------QianrushiFragment .java----------------------------------
public class QianrushiFragment extends Fragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_qianrushi, null, false);
    }
}

-----------------------------fragment_qianrushi.xml-------------------------------------
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout 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"
    tools:context=".fragment.QianrushiFragment">

    <!-- TODO: Update blank fragment layout -->
    <TextView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text="@string/hello_blank_fragment" />

</FrameLayout>

------------------------QianrushiFragment2.java ------------------------------
public class QianrushiFragment2 extends Fragment {

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment

        Button bt = getActivity().findViewById(R.id.btadd);
        bt.setText("new  add");
        return inflater.inflate(R.layout.fragment_qianrushi2, null, false);
    }
}

------------------------------fragment_qianrushi2.xml----------------------------------------------
 <?xml version="1.0" encoding="utf-8"?>
<FrameLayout 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"
    tools:context=".fragment.QianrushiFragment2">

    <!-- TODO: Update blank fragment layout -->
    <TextView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:text="第二个fragment" />

</FrameLayout>

Fragment生命周期：活动、暂停、停止、销毁