2.Fragment 组件化开发入门

2017-01-01 本文已影响0人 KnifeStone

封面.png

public class MyFragment extends Fragment {
    
    private View mLayout;

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

3.怎么使用

使用Fragment标签在布局中使用，在具体节点下放置fragment标签
重要属性:

id ：fragment标签或者父容器，必须设置一个id，不然会报错
tag：给fragment设置一个标签可以在FragmentManager通过tag查找是否存在该实例
name：编写的Fragment地址

<FrameLayout
        android:id="@+id/layoutBanner"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <fragment
            android:id="@+id/fragment_banner"
            android:name="com.zplh.hei.ui.banner.BannerFragment"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:tag="BannerFragment" />

    </FrameLayout>

代码中创建实例 new Fragment() 通过事物添加进布局

Fragment fragment = new MyFragment();
FragmentManager fragmentManager = getFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
//  添加进R.id.container布局中
fragmentTransaction.add(R.id.container, fragment); 
fragmentTransaction.commit();

4.事务API

//获得Fragment管理器
FragmentManager fragmentManager = getFragmentManager();

//获得Fragment事务
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();

//添加一个Fragment
fragmentTransaction.add(int containerViewId, Fragment fragment); 

//替换已添加到容器中的现有片段
fragmentTransaction.replace(int containerViewId, Fragment fragment);

//删除一个现有的片段。如果它被添加到一个容器中，它的视图也从该容器中删除
fragmentTransaction.remove(Fragment fragment);

//提交事务（提交才会生效）
fragmentTransaction.commit();

//添加进事务栈 这时候点击back键 会回滚事务
fragmentTransaction.addToBackStack("tag");

//显示一个Fragment
fragmentTransaction.show(Fragment fragment);

//隐藏一个现有的Fragment
fragmentTransaction.hide(Fragment fragment);

......
更多API 查看源码 android.app.FragmentTransaction

5.数据传递

传递参数

//通过Bundle来给Fragment传递参数
Bundle args = new Bundle();
//设置参数
args.putString("name", "要传递的字符串");
//实例Fragment
Fragment fragment = new StoreFragmentWithArg();
fragment.setArguments(args);

.获得参数

//获取参数
Bundle args = getArguments();
     if (null != args) {
     String name = args.getString("name");
 }

6.状态保存和恢复

保存

private String name;
@Override
public void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    outState.putInt("name", name);
}

恢复

private String name;
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    if (savedInstanceState != null) {
        name = savedInstanceState.getString("name");
    }
}

7.Fragment与Activity交互

private IComm comm;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    Activity activity = getActivity();
    //onCreate，确定是否支持接口
    if (activity instanceof IComm) {
            comm = (IComm) activity;
    }
}
//定义接口 Activity实现接口
public interface IComm {
     void notifyViewCount(String tag, int viewCount);
}

8.生命周期

打印生命周期的方法


public class MyFragment extends Fragment {

    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        log("onAttach");
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        log("onCreate");
    }

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        log("onCreateView：创建视图");
        return super.onCreateView(inflater, container, savedInstanceState);
    }
    @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        log("onViewCreated:在创建视图");
    }

    @Override
    public void onViewStateRestored(Bundle savedInstanceState) {
        super.onViewStateRestored(savedInstanceState);
        log("onViewStateRestored:在视图状态恢复");
    }

    @Override
    public void onStart() {
        super.onStart();
        log("onStart");
    }

    @Override
    public void onResume() {
        super.onResume();
        log("onResume");
    }

    @Override
    public void onPause() {
        super.onPause();
        log("onPause");
    }
    @Override
    public void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        log("onSaveInstanceState:做保存状态");
    }

    @Override
    public void onStop() {
        super.onStop();
        log("onStop");
    }

    @Override
    public void onDestroyView() {
        log("onDestroyView:销毁视图");
        super.onDestroyView();
    }

    @Override
    public void onDestroy() {
        log("onDestroy");
        super.onDestroy();
    }

    private void log(String tag) {
        Log.d("Fragment生命周期", tag);
    }
}

依次执行以下操作控制台的日志输出

首次进入
Fragment生命周期: onAttach
Fragment生命周期: onCreate
Fragment生命周期: onCreateView：创建视图
Fragment生命周期: onViewCreated:在创建视图
Fragment生命周期: onViewStateRestored:在视图状态恢复
Fragment生命周期: onStart
Fragment生命周期: onResume
关闭屏幕
Fragment生命周期: onPause
Fragment生命周期: onSaveInstanceState:做保存状态
Fragment生命周期: onStop
唤醒屏幕
Fragment生命周期: onStart
Fragment生命周期: onResume
退出
Fragment生命周期: onPause
Fragment生命周期: onDestroyView:销毁视图
Fragment生命周期: onDestroy

9.探讨

FragmentManager.findFragmentById findFragmentByTag
Fragment推荐使用于需要复用的组件和需要嵌套组件的需求
Fragment嵌套Fragment

2.Fragment 组件化开发入门

目录

1.fragment是什么

2.编写一个Fragment