3个片段之间的通信

Question

我有 3 个片段。片段 A、B 和 C。A 有一个“继续”按钮，它将把它带到 B。B 有一个继续按钮，它将把它带到 C。C 有一个“添加”按钮，它将把它带回 B。现在我想要在按下继续按钮时将数据从 A 发送到 B。以及按下添加按钮时从 C 到 B。我尝试使用捆绑包。第一次从 A 到 B 时，它给了我空指针异常，来自 C 的包为空。如何解决这个问题？非常感谢任何帮助。请通过下面的代码sn-p

注意：ItemDetails是从fragment A获取的，EmployeeDetails是从fragment C获取的。 Fragment Flow => 1. fragment A 2. A到B(itemsList传递给B) 3. B到C(不通信) 4. 返回从 C 到 B（传递给 B 的员工列表）。

 String TEMP_STRING_EMPLOYEES, TEMP_STRING_ITEMS;
EmployeeList employeeList;
ItemsList itemsList;

@Override
public void onStart() {
    super.onStart();
    Bundle args = getArguments();
    if (args != null) {

        TEMP_STRING_ITEMS = args.getString("ItemsDetails");

        try {
            // Set article based on argument passed in
            TEMP_STRING_EMPLOYEES = args.getString("EmployeeDetails");

        } catch (NullPointerException ex) {

        }


    } else {

    }

}
//Next lines of code from MAinActivity.java

@覆盖 public void onFragmentInteractionForEmployeeDetails(ArrayList arrayList) {

    EmployeeList employeeList = new EmployeeList(arrayList);
    String correspondingJson = NavigationUtils.getStringForObject(employeeList);

    B newFragment = new B();
    Bundle args = new Bundle();
    args.putString("EmployeeDetails", correspondingJson);
    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);
    transaction.commit();
}

Answer 1

您可以在 Fragment 中使用回调，并且 Activity 存储您的对象。

活动

public class MyActivity extends Activity implements MyActivityCallback{

    private Object myObject; // Replace with your object type

    @Override 
    public Object getMyObject(){
         return myObject;
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        myObject = new Object();
        // ...
    }

    // ....
}

MyActivityCallback

public interface MyActivityCallback{
   Object getMyObject();
}

片段

private MyActivityCallback mCallback;

@Override
public void onAttach(Context context) {
    super.onAttach(context);

    try {
        mCallback = (MyActivityCallback) getActivity();
    } catch (ClassCastException e) {
        throw new ClassCastException(context.toString()
                + " must implement " + MyActivityCallback.class.getSimpleName());
    }
}

@Override
public void onDetach() {
    mCallback = null;
    super.onDetach();
}

然后在您的 Fragment 中，访问您的对象 mCallback.getMyObject();