Fragment与Fragment之间交互

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装载自:https://developer.android.com/training/basics/fragments/communicating.html

Fragment与Fragment之间交互

首先我们必须知道Fragment是依附于Activity的,所有以Fragment 之间的交互应通过与之关联的 Activity 来完成,两个 Fragment 之间不应直接交互.

1.定义接口方法进行交互

在 Fragment 类中定义一个接口，并在 Activity 中实现。Fragment 在它的 onAttach() 方法生命周期中获取该接口的实现，然后调用接口的方法.Fragment在生命周期onAttach() 获取接口实现方法,调用的接口方法和Activity进行交互.

举例:

public class HeadlinesFragment extends ListFragment {    OnHeadlineSelectedListener mCallback;    // Container Activity must implement this interface    public interface OnHeadlineSelectedListener {        public void onArticleSelected(int position);    }    @Override    public void onAttach(Activity activity) {        super.onAttach(activity);        // This makes sure that the container activity has implemented        // the callback interface. If not, it throws an exception        try {            mCallback = (OnHeadlineSelectedListener) activity;        } catch (ClassCastException e) {            throw new ClassCastException(activity.toString()                    + " must implement OnHeadlineSelectedListener");        }    }    ...}

现在 Fragment 可以通过调用 mCallback（OnHeadlineSelectedListener 接口的实例）的 onArticleSelected() 方法（或者接口的方法其它方法）与 Activity 进行消息传递。

比如,当用户在frgment中点击一条item时候.Fragment回调接口将事件传递给父 Activity。

 @Override    public void onListItemClick(ListView l, View v, int position, long id) {        // Send the event to the host activity        mCallback.onArticleSelected(position);    }

实现接口

为了接收来自Fragment中的回调,其宿主Activity必须实现Fragment中的接口.

举例:

public static class MainActivity extends Activity        implements HeadlinesFragment.OnHeadlineSelectedListener{    ...    public void onArticleSelected(int position) {        // The user selected the headline of an article from the HeadlinesFragment        // Do something here to display that article    }}

发送一条消息至Fragment

宿主Activity 能够发送信息至一个fragment,通过findFragmentById()方法获取Fragment的实例,然后直接调用frgment里面的公共方法向Fragment传递事件.

public static class MainActivity extends Activity        implements HeadlinesFragment.OnHeadlineSelectedListener{    ...    public void onArticleSelected(int position) {        // The user selected the headline of an article from the HeadlinesFragment        // Do something here to display that article        ArticleFragment articleFrag = (ArticleFragment)                getSupportFragmentManager().findFragmentById(R.id.article_fragment);        if (articleFrag != null) {            // If article frag is available, we're in two-pane layout...            // Call a method in the ArticleFragment to update its content            articleFrag.updateArticleView(position);        } else {            // Otherwise, we're in the one-pane layout and must swap frags...            // Create fragment and give it an argument for the selected article            ArticleFragment newFragment = new ArticleFragment();            Bundle args = new Bundle();            args.putInt(ArticleFragment.ARG_POSITION, position);            newFragment.setArguments(args);            FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();            // Replace whatever is in the fragment_container view with this fragment,            // and add the transaction to the back stack so the user can navigate back            transaction.replace(R.id.fragment_container, newFragment);            transaction.addToBackStack(null);            // Commit the transaction            transaction.commit();        }    }}

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