两个片段之间的通信 - 这是正确的方式？

Question

我已阅读this手册，同时我正在阅读this书。 developer.android.com说我应该通过活动来实现沟通。但是这本书说我可以使用setTargetFragment()并手动调用onActivityResult（）从其他片段的目标片段。每种方法都有效，但哪一种是正确的什么是setTargetFrament（），如果我不能用它与其他片断进行通信？

Answer 1

setTargetFrament（）和getTargetFrament（）可用于启动另一个片段的片段的上下文中。第一个片段可以通过其自身作为对第二个片段的引用：

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()直接检索从oldFrag的oldFrag和访问方法。

然而，这并不是建议在平常的基础上使用的东西。

片段之间的通信的推荐方法是通过父活动来完成，作为docs提及：

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：

的布局的主要活动：

<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); 
    } 
}