什麼是startActivityForResult（）的模擬，但使用片段

Question

我有4個選項卡，每選中一個片段。
從選項卡＃2片段我想要啓動另一個片段在選項卡＃2上運行並從中獲取結果。什麼是正確的方法來做到這一點？有沒有例子？

如果這些是活動，而不是片段，我知道我會用startActivityForResult（）。

Answer 1

有一個片段交互的推薦模式。您的每一個片段的聲明它需要與使用接口他人互動的方式：

這裏的第一個片段的代碼：

public class Fragment1 { 
    private Listener listener; 

    @Override 
    public void onCreateView(...) { 
     Bundle args=getArguments();    
     if (args!=null) { 
      Object arg=args.getParcelable("result"); 
      //use the result for something 
     } 

     //... 
     someView.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
       if (listener!=null) 
        listener.onFragment2Requested(); 
      } 
     }); 
     //... 
    } 

    @Override 
    public void onAttach(Activity activity) { 
     super.onAttach(activity); 

     this.listener=(Listener) activity; 
    } 

    public interface Listener { 
     public void onFragment2Requested(); 
    } 
} 

和第二個片段：

public class Fragment2 { 
    private Listener listener; 

    @Override 
    public void onCreateView(...) { 
     //... 
     someView.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
       Object object=... 

       if (listener!=null) 
        listener.onWorkDone(object); 
      } 
     }); 
     //... 
    } 

    @Override 
    public void onAttach(Activity activity) { 
     super.onAttach(activity); 

     //will throw ClassCastException unless your Activity 
     //implements Listener interface of your fragment 
     this.listener=(Listener) activity; 
    } 

    public interface Listener { 
     public void onWorkDone(Object someResult); 
     public void someOtherMethod(); 
    } 
} 

，然後，最後，你的Activity，作爲協調者：

public class YourActivity extends 
           FragmentActivity 
          implements 
           Fragment1.Listener, 
           Fragment2.Listener { 

    public void onFragment2Requested() { 
     Fragment2 frg2=new Fragment2(); 
     //here goes your code to switch fragments the way you want  
    } 

    public void onWorkDone(Object someResult) { 
     //if you don't want to create new instance of fragment each time 
     //you can try to get it from FragmentManager. 
     //But don't try to store reference to it anywhere (activity field etc.) 
     //it could interfere with fragment recycling mechanism 
     Fragment1 frg1=new Fragment1(); 
     Bundle args=new Bundle(); 
     args.putParcelable("result", someResult); 
     //instead of arguments, you could use setter method, but that way 
     //your Object is lost when fragment is recreated upon orientation change, etc. 
     frg1.setArguments(args); 
     //here goes your code to switch fragments the way you want 
    } 

    public void someOtherMethod() { 
     //... 
    } 
} 

我知道，這可能看起來太多代碼，但這是它完成的方式。 此外，此模式涵蓋了in this article。