两个片段之间的通信-哪种方法正确? [英] Communication between two fragments - which is right way?

问题描述

我已经阅读了此手册，我也在阅读这本书.developer.android.com说我应该通过活动来实现交流.但是这本书说我可以使用 setTargetFragment()并手动调用onActivityResult()来获取其他片段中的目标片段.每种方法都有效，但是哪个正确?如果我不能将setTargetFrament()用于与其他片段进行通信，则该使用什么?

I have read this manual and also i'm reading this book. developer.android.com says i should implement communication through activity. But the book says i can use setTargetFragment() and call onActivityResult() by hand for target fragment from other fragment. Each approach works but which is right? What is setTargetFrament() for, if i can't use it for communication with other fragment?

推荐答案

setTargetFrament()和getTargetFrament()可以在一个片段的上下文中使用，该片段开始另一个片段.第一个片段可以将自身传递为对第二个片段的引用:

setTargetFrament() and getTargetFrament() can be used in the context of one fragment that starts another fragment. The first fragment can pass its self as a reference to the second fragment:

MyFragment newFrag = new MyFragment();
newFrag.setTargetFragment(this, 0);
getFragmentManager().beginTransaction().replace(R.id.frag_one, newFrag).commit();

现在newFrag可以使用 getTargetFrament()来检索oldFrag并直接从oldFrag中访问方法.

Now newFrag can use getTargetFrament() to retrieve the oldFrag and access methods from oldFrag directly.

但是，这不是建议通常使用的东西.

This is not however something that is recommanded to be used on an usual basis.

片段之间的通讯方式建议通过父活动完成，例如文档提及:

The recommanded way of communication between fragments is to be done through the parent activity, as the docs mention:

Often you will want one Fragment to communicate with another, 
for example to change the content based on a user event. 
All Fragment-to-Fragment communication is done through the associated Activity. 
Two Fragments should never communicate directly.

下面是一个例子:

主要活动的布局:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >
    <FrameLayout 
        android:id="@+id/frag_one"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"/>
    <FrameLayout 
        android:id="@+id/frag_two"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"/>
</LinearLayout>

活动:

public class MainActivity extends Activity
{
    private MyFragment f1;
    private MyFragment f2;

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

        Bundle b1 = new Bundle();
        b1.putString("name", "Fragment One");
        f1 = MyFragment.createNew(b1);//we create a new fragment instance
        f1.setOnReceiveListener(new MyFragment.ReceiveListener()//we create a new ReceiveListener and pass it to the fragment
        {
            @Override
            public void recv(String str)
            {
                //f1 has sent data to the activity, the activity passes forward to f2 
                f2.send(str);
            }
        });
        //we attach the fragment to the activity
        getFragmentManager().beginTransaction().add(R.id.frag_one, f1, "frag_one").commit();


        //we repeat the above process for the second fragment
        Bundle b2 = new Bundle();
        b2.putString("name", "Fragment Two");
        f2 = MyFragment.createNew(b2);
        f2.setOnReceiveListener(new MyFragment.ReceiveListener()
        {
            @Override
            public void recv(String str)
            {
                f1.send(str);
            }
        });
        getFragmentManager().beginTransaction().add(R.id.frag_two, f2, "frag_two").commit();        
    }
}

片段布局:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >
    <Button 
        android:id="@+id/frag_btn"
        android:layout_height="wrap_content"
        android:layout_width="match_parent"
        android:layout_alignParentTop="true"/>
    <TextView
        android:id="@+id/frag_txt"
        android:layout_height="match_parent"
        android:layout_width="match_parent"
        android:layout_below="@+id/frag_btn"
        android:textSize="10sp"/>
</RelativeLayout>

片段类:

public class MyFragment extends Fragment
{
    private ReceiveListener recv_list;
    private Button btn;
    private TextView txt;

    //static factory function that creates new fragments  
    public static MyFragment createNew(Bundle b) 
    {
        MyFragment f = new MyFragment();
        f.setArguments(b);
        return f;
    }

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

    @Override
    public void onViewCreated(View view, Bundle savedInstanceState)
    {
        super.onViewCreated(view, savedInstanceState);

        btn = (Button) view.findViewById(R.id.frag_btn);
        txt = (TextView) view.findViewById(R.id.frag_txt);

        //we retrieve the passed arguments (in this case the name)
        Bundle b = getArguments();
        final String name = b.getString("name");

        btn.setText(name);
        btn.setOnClickListener(new View.OnClickListener()
        {
            @Override
            public void onClick(View v)
            {
                if(null != recv_list)
                {
                    //now we pass the data to the parent activity
                    recv_list.recv(name + " says hello!");
                }
            }
        });
    }

    //the activity passes data to the fragment using this method
    public void send(String s)
    {
        txt.append(s + "\n");
    }

    //helper method that will set the listener
    public void setOnReceiveListener(ReceiveListener l)
    {
        recv_list = l;
    }

    //the declaration of the listener
    public interface ReceiveListener
    {
        public void recv(String str);
    }
}

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