Java 如何创建一个接口以从 Fragment 获取信息到 Android Activity？

How to create an interface to get info from a Fragment to an Android Activity?

提问by kramer65

Over the past days I've desperately been trying to build an android app with a simple fragment (which I use twice). I want to pass the contents of the fragments' EditText-boxes to a new activity. I just can't figure out how to get those contents from the fragments. What I have so far is this:

在过去的几天里，我一直在拼命尝试用一个简单的片段（我用过两次）来构建一个 android 应用程序。我想将片段的 EditText 框的内容传递给新活动。我只是不知道如何从片段中获取这些内容。到目前为止，我所拥有的是：

I've got my edit_text_fragment.xml:

我有我的edit_text_fragment.xml：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >
    <EditText 
        android:id="@+id/my_edit_text"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:hint="my hint" />
</LinearLayout>

and the corresponding MyEditTextFragment.java:

和相应的MyEditTextFragment.java：

public class MyEditTextFragment extends Fragment {
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.edit_text_fragment, container, false);
        return view;
    }
}

I then use this fragment twice in my main.xmllike this:

然后我main.xml像这样使用这个片段两次：

<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">
    <fragment 
        android:id="@+id/detailfragment_placeholder"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        class="com.example.fragmenttester5.MyEditTextFragment" />
    <fragment 
        android:id="@+id/detailfragment_placeholder2"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        class="com.example.fragmenttester5.MyEditTextFragment" />
    <Button 
        android:id="@+id/submit_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Submit all of it" />
</LinearLayout>

and in my MainActivity I hooked up the button to a new activity:

在我的 MainActivity 中，我将按钮连接到一个新活动：

public class MainActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Button submitButton = (Button) findViewById(R.id.submit_button);
        submitButton.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v){
                Intent intent = new Intent(MainActivity.this, OtherActivity.class);
                intent.putExtra("result1", "the_result_from_the_first_editText");
                intent.putExtra("result2", "the_result_from_the_second_editText");
                startActivity(intent);
            }
        });
    }
}

I thinkI now need to define some kind of interface in the Fragment, but I can't find how. I read a couple examples and tutorials (like this one), but they make no sense to me at all. I don't understand the code given and I just don't understand how to adjust it for my use case.

我想我现在需要在 Fragment 中定义某种接口，但是我找不到方法。我读了几个例子和教程（比如这个），但它们对我来说根本没有意义。我不明白给出的代码，我只是不明白如何为我的用例调整它。

So my question; can anybody help me to get the contents of the fragment from within the activity? Examples would be very very welcome since I'm just banging my head against the wall here..

所以我的问题; 有人可以帮我从活动中获取片段的内容吗？示例将非常受欢迎，因为我只是在这里用头撞墙..

采纳答案by Paul Burke

So you'd create an Interface to talk with the Activityif the event happened inthe Fragment. For situations like this, you can simply make an accessible method in the Fragmentthat the Activitycan call. So

所以，你会创建一个接口与谈话Activity，如果事件发生在的Fragment。对于这种情况，您可以简单地Fragment在Activity可以调用的方法中创建一个可访问的方法。所以

public class MyEditTextFragment extends Fragment {
    private EditText mEditText;

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

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);

        mEditText = (EditText) getView().findViewById(R.id.my_edit_text);
    }

    public Editable getText() {
        return mEditText.getText();
    }
}

Then

然后

public class MainActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        final MyEditTextFragment fragment1 = (MyEditTextFragment)
            getFragmentManager().findFragmentById(R.id.detailfragment_placeholder);

        final MyEditTextFragment fragment2 = (MyEditTextFragment)
            getFragmentManager().findFragmentById(R.id.detailfragment_placeholder2);

        Button submitButton = (Button) findViewById(R.id.submit_button);
        submitButton.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v){

                String firstResult = fragment1.getText().toString();
                String secondResult = fragment2.getText().toString();

                Intent intent = new Intent(MainActivity.this, OtherActivity.class);
                intent.putExtra("result1", firstResult);
                intent.putExtra("result2", secondResult);
                startActivity(intent);
            }
        });
    }
}

This assumes that you assigned the Fragmenttags in your FragmentTransaction. Be sure to check for null Fragments(omitted for brevity)

这假设您Fragment在FragmentTransaction. 一定要检查 null Fragments（为简洁起见省略）

回答by Dan Lew

On a high level, there are two tasks that you commonly need to solve with Fragments. The first is communicating data from an Activity to a Fragment. The second is communicating data from a Fragment to an Activity.

在高层次上，您通常需要使用 Fragment 解决两个任务。第一个是将数据从 Activity 传送到 Fragment。第二个是将数据从 Fragment 传送到 Activity。

An Activity knows which Fragments it contains since it creates them, so it's easy to communicate that way - just call methods on the Fragment itself. But the inverse is not true; Fragments might be attached to any number of random Activities, so it doesn't know anything about it's parent.

Activity 知道它包含哪些 Fragment，因为它创建了它们，因此很容易以这种方式进行通信 - 只需调用 Fragment 本身的方法即可。但反之则不然。Fragments 可能附加到任意数量的随机活动，因此它不知道它的父级。

The solution is to implement an interface that the Activity implements and the Fragment knows how to communicate with. That way, your Fragment has something it knows how to talk with. There are specific code examples for how to do it here: http://developer.android.com/guide/components/fragments.html#CommunicatingWithActivity

解决方案是实现一个接口，Activity 实现和 Fragment 知道如何与之通信。这样，你的 Fragment 就有了它知道如何与之交谈的东西。这里有具体的代码示例：http: //developer.android.com/guide/components/fragments.html#CommunicatingWithActivity

(In particular, check out the "Creating event callbacks to the activity" code examples).

（特别是，请查看“创建活动的事件回调”代码示例）。

回答by Ridcully

You are right, that's kind of a standard way to pass data from a Fragment to an activity.

您说得对，这是将数据从 Fragment 传递到活动的一种标准方式。

Basically you define a Listenerinterface which the Activity implements, and the Activity registers itself as a Listener with the Fragment.

基本上，您定义了一个ListenerActivity 实现的接口，并且 Activity 将自己注册为 Fragment 的侦听器。

Here's a simple example:

这是一个简单的例子：

Fragment

分段

class MyFragment extends Fragment {

    interface Listener {
        public void somethingHappenedInFragment(Object... anyDataYouWantToPassToActivity);
    }

    private Listener mListener;

    public void setListener(Listener listener) {
        mListener = listener;
    }

    // ... your code ...

    // Now here you pass the data to the activity
    mListener.somethingHappenedInFragment(some, data);

    // ... more of your code
 }

Activity

活动

public MyActivity extends Activity implements MyFragment.Listener {

    // ... your code ...

    // creating the Fragment
    MyFragment f = new MyFragment();

    // register activity as listener
    f.setListener(this);

    // ... more of your code

    // implementation of MyFragment.Listener interface
    @Override
    public void somethingHappenedInFragment(Object... anyDataYouWantToPassToActivity) {
        // here you have the data passed from the fragment.
        for (Object o : anyDataYouWantToPassToActivity {
            System.out.println(o.toString();
        }
    }

}

回答by Albert Nguyen

Activity will be received data from updateDetail() method in Fragment

Activity 将从 Fragment 中的 updateDetail() 方法接收数据

//// Activity 
public class RssfeedActivity extends Activity implements MyListFragment.OnItemSelectedListener {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_rssfeed);
        Button btn = (Button) findViewById(R.id.btn);
        btn.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                Log.d("Annv - Fragment", "onClick here");
            }
        });
    }

    // if the wizard generated an onCreateOptionsMenu you can delete
    // it, not needed for this tutorial

    @Override
    public void onRssItemSelected(String link) {
        //        DetailFragment fragment = (DetailFragment) getFragmentManager()
        //                .findFragmentById(R.id.detailFragment);
        //        if (fragment != null && fragment.isInLayout()) {
        //          fragment.setText(link);
        //        } 
        //        Intent start = new Intent(this, RssfeedSecondActivity.class);
        //        startActivity(start);
        DetailFragment fragment = (DetailFragment) getFragmentManager()
                .findFragmentById(R.id.detailFragment);
        if (fragment != null && fragment.isInLayout()) {
            fragment.setText(link);
        }
    }

}

/// Fragment
public class MyListFragment extends Fragment {

    private OnItemSelectedListener listener;
    private OnItemStartActivityListener listenerStartAct;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_rsslist_overview,
                container, false);
        Button button = (Button) view.findViewById(R.id.button1);
        Log.d("Annv - Fragment", "run on " + getActivity().toString());
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                updateDetail();
            }
        });
        return view;
    }

    public interface OnItemSelectedListener {
        public void onRssItemSelected(String link);
    }

    public interface OnItemStartActivityListener {
        public void onRssStartActivity(String link);
    }

    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
        if (activity instanceof OnItemSelectedListener) {
            Log.d("Annv - Fragment", "activity " + activity.getLocalClassName());
            listener = (OnItemSelectedListener) activity;
        } else if (activity instanceof OnItemStartActivityListener) {
            Log.d("Annv - Fragment", "activity " + activity.getLocalClassName());
            listenerStartAct = (OnItemStartActivityListener) activity;
        } else {
            throw new ClassCastException(activity.toString()
                    + " must implemenet MyListFragment.OnItemSelectedListener");
        }
    }

    // May also be triggered from the Activity
    public void updateDetail() {
        // create fake data
        //        String newTime = String.valueOf(System.currentTimeMillis());
        //        // Send data to Activity
        //        listenerStartAct.onRssItemSelected(newTime);
        if (getActivity() instanceof OnItemSelectedListener) {
            listener.onRssItemSelected("start start");
        } else {
            String newTime = String.valueOf(System.currentTimeMillis());
            listenerStartAct.onRssStartActivity(newTime);
        }

    }

}