如何使用回调接口从 Mainactivity 与 Fragment 进行通信？

Question

我有四个菜单的导航抽屉，每个菜单都有自己的片段 , 在第一个片段内部有视图分页器滑动选项卡和 2 个片段，

Activity_main.xml

    <?xml version="1.0" encoding="utf-8"?>
    <android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:id="@+id/drawer_layout"
        android:layout_height="match_parent"
        android:layout_width="match_parent"
        android:fitsSystemWindows="true">

    <android.support.design.widget.CoordinatorLayout  
        xmlns:app="http://schemas.android.com/apk/res-auto"
        android:id="@+id/main_content"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <android.support.design.widget.AppBarLayout
            android:id="@+id/appbar"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:animateLayoutChanges="true"
            android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">

            <android.support.v7.widget.Toolbar
                android:id="@+id/toolbar"
                android:layout_width="match_parent"
                android:layout_height="?attr/actionBarSize"
                android:background="?attr/colorPrimary"
                app:popupTheme="@style/ThemeOverlay.AppCompat.Light" />

            <android.support.design.widget.TabLayout
                android:id="@+id/tabs"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                app:tabIndicatorColor="@color/white"
                app:tabIndicatorHeight="4dp" />

        </android.support.design.widget.AppBarLayout>

////////////// Here I'm replacing each fragments ////////////////
        <FrameLayout   
            android:id="@+id/main_content_framelayout"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:layout_behavior="@string/appbar_scrolling_view_behavior" />

        <android.support.design.widget.FloatingActionButton
            android:id="@+id/fab"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="end|bottom"
            android:layout_margin="@dimen/fab_margin"
            android:src="@drawable/ic_done"
            android:visibility="gone"/>

    </android.support.design.widget.CoordinatorLayout>


        <android.support.design.widget.NavigationView
            android:id="@+id/nav_view"
            android:layout_height="match_parent"
            android:layout_width="wrap_content"
            android:layout_gravity="start"
            android:fitsSystemWindows="true"
            app:headerLayout="@layout/nav_header"
            app:menu="@menu/drawer_view"/>

    </android.support.v4.widget.DrawerLayout>

ManinActivity-DrawerSelection

 public void selectDrawerItem(MenuItem menuItem) {
        // Create a new fragment and specify the fragment to show based on nav item clicked
        Fragment fragment = null;
        Class fragmentClass = null;

        switch (menuItem.getItemId()) {
            case R.id.nav_home:
                fragmentClass = Home_Tab_Fragment.class;
                break;
            case R.id.nav_myorders:
                fragmentClass = SecondFragment.class;
                break;
            case R.id.nav_myoffers:
                fragmentClass = ThirdFragment.class;
                break;
            case R.id.nav_notification:
                fragmentClass = FourthFragment.class;
                break;

        }

                fragment = (Fragment) fragmentClass.newInstance();
                FragmentManager fragmentManager = getSupportFragmentManager();
                fragmentManager.beginTransaction().replace(R.id.main_content_framelayout, fragment).commit();
                mDrawerLayout.closeDrawers();

}

HomeTabFragment

public class Home_Tab_Fragment extends Fragment {

    private FragmentActivity myContext;
    ViewPager viewPager;
    TabLayout tabLayout;
    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View rootView =  inflater.inflate(R.layout.layout_viewpager, container, false);
          viewPager = (ViewPager) rootView.findViewById(R.id.view_pager);
        return rootView;
    }

    @Override
    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        SlidingTabAdapter adapter = new SlidingTabAdapter(getChildFragmentManager());
        adapter.addFragment(new FirstTabFragment(), "First TAB");
        adapter.addFragment(new SecondTabFragment(), "Second Tab");
        viewPager.setAdapter(adapter);
        tabLayout = (TabLayout) getActivity().findViewById(R.id.tabs);
        tabLayout.setVisibility(View.VISIBLE);
        tabLayout.setupWithViewPager(viewPager);
    }

}

SlidingTabAdapter

public class SlidingTabAdapter extends FragmentPagerAdapter {

    private final List<Fragment> mFragments = new ArrayList<>();
    private final List<String> mFragmentTitles = new ArrayList<>();

    public SlidingTabAdapter(FragmentManager fm) {
        super(fm);
    }

    public void addFragment(Fragment fragment, String title) {
        mFragments.add(fragment);
        mFragmentTitles.add(title);
    }

    @Override
    public Fragment getItem(int position) {
        return mFragments.get(position);
    }

    @Override
    public int getCount() {
        return mFragments.size();
    }

    @Override
    public CharSequence getPageTitle(int position) {
        return mFragmentTitles.get(position);
    }
}

layout_viewpager.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.view.ViewPager
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/view_pager"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

第一个片段

public class FirstTabFragment extends Fragment {

    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
     View rootView = inflater.inflate(R.layout.fragment_first, container, false);
        getActivity().setTitle("Foodies");
        return rootView ;
    }

  public void updateFirstFragmentValues(){
      //Doing some operations
  }

}

在 MainActivity 里面，我想调用 FirstTabFragment 方法 [updateFirstFragmentValues()]

我尝试在 FirstTabFragment 中添加 TAG，

public static final String TAG ="FirstTabFragment.TAG";

然后我像下面这样在 MainActivity 中调用，但 Fragment 始终为空。

 public void invokeMethodFromFirstTabFragment() {
        FragmentManager fm = this.getSupportFragmentManager();
        FirstTabFragment fb=(FirstTabFragment)fm.findFragmentByTag(FirstTabFragment.TAG);
        if (null != fb) {
            fb.updateFirstFragmentValues();
        }else{
            L.m("Fragment is null===========");
        }
    }

请告知，如何从“MainActivity”中调用“FirstTabFragment”方法

请注意 FirstTabFragment 不直接添加到 MainActivity ， 它通过“Home_Tab_Fragment”添加。

Answer 1

好的，阅读您的所有回复，我知道您只需要在创建时将数据传递给片段并能够执行片段的一些方法。好的，很简单：

IMessageFragment 接口

public interface IMessageFragment {
  /**
   * Method to receive new message text
   * @param text Message text to receive
   */
   void updateMessageText(String text);
}

消息片段

public class MessageFragment extends Fragment implements IMessageFragment {
  /**
   * Bind views using ButterKnife
   */
  @BindView(R.id.textView) TextView mTextView;

  /**
   * Bundle data
   */
  private String mMessageText;

  /**
   * Unique id of bundle data
   */
  private static final String MESSAGE_EXTRA_KEY = "f_message";

  /**
   * New fragment pattern. This is pretty much all the magic PLUS this
   * looks by far better than `new Fragment()` upon instatiation
   */
  public static MessageFragment newFragment(String message) {
      // 1. Create new fragment
      MessageFragment auctionFragment = new MessageFragment();
      // 2. Create bundle for fragment params
      Bundle args = new Bundle();
      // 3. Put position
      args.putString(MESSAGE_EXTRA_KEY, message);
      // 4. Set arguments
      auctionFragment.setArguments(args);
      return auctionFragment;
  }


  @Nullable
  @Override
  public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
      View view = inflater.inflate(R.layout.tutorial_fragment, container, false);

      /**
       * Bind views
       */
      ButterKnife.bind(this, view);

      // Update UI
      updateUI();

      return view;
  }

  /**
   * Method to update value of mTextView
   */
  private void updateUI() {
      if(!mMessageText.equals("")) {
          mTextView.setText(mMessageText);
      }
  }

  @Override
  public void updateMessageText(String text) {
      mMessageText = text;
      updateUI();
  }
}

东西非常简单，界面的存在只是为了良好的代码风格和支持设计模式。

Answer 2

编辑：

您不能从 MainActivity 直接访问 FirstTabFragment 方法。首先，您必须从活动中调用Home_Tab_Fragment 方法。然后从该方法中您可以调用FirstTabFragment 方法。

这里是策略：

第 1 步：Home_Tab_Fragment 到 FirstTabFragment 通信

定义这样的接口

public interface IHomeToFirstFragmentController{
          void firstFragmentMethod();
    } 

现在在您的FirstTabFragment 中实现IHomeToFirstFragmentController。那么你必须实现firstFragmentMethod()。

@overrride
    void firstFragmentMethod(){

    }

使用这种方式从Home_Tab_Fragment调用这个firstFragmentMethod方法

YOUR_fragmentInstance.firstFragmentMethod();

第 2 步： 活动至Home_Tab_Fragment：

定义这样的接口

public interface IActivityToHomeTabController{
          void callFirstFragment();
    }

现在在您的Home_Tab_Fragment 中实现IFragmentController。那么你必须实现callFirstFragment()。

@overrride
void callFirstFragment(){
  YOUR_fragmentInstance.firstFragmentMethod();
}

编辑 2：

使用这种方式调用片段

((IFragmentController)YOUR_fragmentInstance).firstFragmentMethod();

希望这能让您对这些主题有所了解。欲了解更多信息，请访问this answer

Answer 3

首先，你创建界面：

public interface CallBackListener{
      void onCallBack();
}

在片段中

public MyFragment extends Fragment{
    private CallBackListener mCallBack;

    @Override
    public void onAttach(Context context) {
        AppCompatActivity activity;
        if (context instanceof AppCompatActivity) {
            activity = (AppCompatActivity) context;
            try {
                mCallBack= (CallBackListener ) activity;
            } catch (ClassCastException e) {
                throw new ClassCastException(activity.toString() + " class must be implement" +
                        " OnBackFragmentListener");
            }
        }
        super.onAttach(context);
    }
}

使用：

mCallBack.onCallBack();

而在Activity中，你必须实现接口：

public MyActivity extends AppCompatActivity implements CallBackListener{

   @Override
   public void onCallBack(){
   // Do somethings here...
   }
}