Fragment的简单Demo

简介

Fragment 是碎片化的 Activity，是 Activity 的模块化组成部分。例如，可以在 Activity 中使用多个 Fragment 来构建多窗格 UI，以及在多个 Activity 中重复使用某个 Fragment。
Fragment 必须依赖 Activity 存在，其生命周期直接受到宿主 Activity 生命周期的影响。 例如，当 Activity 暂停时，其中所有的 Fragment 也会暂停；当 Activity 被销毁时，所有 Fragment 也会被销毁。

开始Demo编写

目录结构总览：

image.png

界面总览：

image.png

主界面布局:activity_main.xml

<?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=".MainActivity">
<!-- LinearLayout 左侧任务栏-->
   <LinearLayout
       android:orientation="vertical"
       android:layout_weight="1"
       android:layout_width="0dp"
       android:layout_height="match_parent">
       <Button
           android:id="@+id/bt_1"
           android:text="1"
           android:layout_width="wrap_content"
           android:layout_height="0dp"
           android:layout_weight="1"/>
       <Button
           android:id="@+id/bt_2"
           android:text="2"
           android:layout_width="wrap_content"
           android:layout_height="0dp"
           android:layout_weight="1"/>


   </LinearLayout>
    <!-- LinearLayout 左侧任务栏-->
    <LinearLayout
        android:orientation="vertical"
        android:layout_weight="8"
        android:layout_width="0dp"
        android:layout_height="match_parent">
<FrameLayout
    android:layout_weight="1"
    android:layout_width="match_parent"
    android:layout_height="0dp">
    <fragment
        android:id="@+id/fragment_up"
        android:layout_width="match_parent"
        android:name="com.example.lp.myfragment.upFragment"
        android:layout_height="match_parent"
        />

</FrameLayout>
        <FrameLayout
            android:id="@+id/fragment_donw"
            android:layout_weight="9"
            android:layout_width="match_parent"
            android:layout_height="0dp">


        </FrameLayout>

    </LinearLayout>
</LinearLayout>

上方fragment布局：fragment_up.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=".upFragment">

    <!-- TODO: Update blank fragment layout -->
    <TextView
        android:id="@+id/tv_up"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        />

</FrameLayout>

下方fragment布局1（2）：fragment_down01.xml：（布局fragment_down02.xml与之相同）

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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:orientation="vertical"
    tools:context=".down01Fragment">

    <TextView
        android:id="@+id/tv_01"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        />

</LinearLayout>

upFragment：

public class upFragment extends Fragment {
    private static final String TAG="upFragment";
    private TextView textView;

    public upFragment() {
        // Required empty public constructor
        Log.i(TAG, "upFragment: ");
    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        Log.i(TAG, "onCreateView: ");
        View view= inflater.inflate(R.layout.fragment_up, container, false);
        textView=view.findViewById(R.id.tv_up);
        textView.setText("测试上方碎片");
        textView.setTextColor(Color.BLUE);
        return view;
    }



    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
        Log.i(TAG, "onAttach: ");

    }

    @Override
    public void onDetach() {
        super.onDetach();
        Log.i(TAG, "onDetach: ");

    }

}

down01Fragment: (down02Fragment相同)

public class down01Fragment  extends Fragment {
    private static final String TAG="down01Fragment";
    private TextView textView;

    public down01Fragment() {
        // Required empty public constructor
        Log.i(TAG, "down01Fragment: ");
    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        Log.i(TAG, "down01Fragment onCreateView: ");
        View view= inflater.inflate(R.layout.fragment_down01, container, false);
        textView=view.findViewById(R.id.tv_01);
        textView.setTextColor(Color.GREEN);
        textView.setText("down01Fragment");
        return view;
    }



    @Override
    public void onAttach(Activity activity) {
        Log.i(TAG, "down01Fragment onAttach: ");
        super.onAttach(activity);

    }

    @Override
    public void onDetach() {
        Log.i(TAG, "down01Fragment onDetach: ");
        super.onDetach();

    }

}

MainActivity：

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
    private static final String TAG="MainActivity";
    private FragmentTransaction fragmentTransaction;

    private down01Fragment down01Fragment;
    private down02Fragment down02Fragment;

    private Button button1;
    private Button button2;

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

    private void initFragment() {
        Log.i(TAG, "initFragment: ");
       //fragmentTransaction=getFragmentManager().beginTransaction();
        fragmentTransaction=getSupportFragmentManager().beginTransaction();
        down01Fragment=new down01Fragment();
        down02Fragment=new down02Fragment();
        fragmentTransaction.replace(R.id.fragment_donw,down01Fragment);//replace的形式是每次都刷新，add show不会刷新，只是hide隐藏起来
        fragmentTransaction.commit();

    }

    private void initView() {
        Log.i(TAG, "initView: ");
        button1=findViewById(R.id.bt_1);
        button2=findViewById(R.id.bt_2);
        button1.setOnClickListener(this);
        button2.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()){
            case R.id.bt_1:
                fragmentTransaction.replace(R.id.fragment_donw,down01Fragment);
                fragmentTransaction.commit();
                break;
            case R.id.bt_2:
                fragmentTransaction.replace(R.id.fragment_donw,down02Fragment);
                fragmentTransaction.commit();
                break;
        }
    }
}

需要注意的是，fragment和v4包中的app.fragment的使用的区别
android.support.v4.app.Fragment：可以兼容到安卓1.6的版本
v4包下的fragment所在的activity必须继承FragmentActivity，否则会报错。
使用v4时，FragmentTransaction 的创建要使用：
FragmentTransaction fragmentTransaction=getSupportFragmentManager().beginTransaction();
getFragmentManager（）对应的是 app；
功能上没啥区别。

附上demo链接：https://github.com/CodeLpea/PracticceOfAndorid.git

image.png

fragment还有add show的形式展示，有空可以自己尝试一下哈。
demo中删了两行代码，会造成app挂掉，
试试找出来哈，自己写一遍的代码才是自己的，对吧。
谢谢观看。