Question

所以我有MainActivity.java，我也有FragmentA.java和FragmentB.java。

在我的MainActivity中，我有一个BottomNavigation，可让我在两个片段之间进行切换。

MainActivity.java

private BottomNavigationView.OnNavigationItemSelectedListener navListener = new BottomNavigationView.OnNavigationItemSelectedListener() {
    @Override
    public boolean onNavigationItemSelected(@NonNull MenuItem menuItem) {
        Fragment selectedFragment = null;
        switch (menuItem.getItemId()) {
            case R.id.nav_a:
                selectedFragment = new FragmentA();
                break;
            case R.id.nav_b:
                selectedFragment = new FragmentB();
                break;
        }

        getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container, selectedFragment).commit();

        return true;
    }
};

在FragmentA内，我有一个RecyclerView，当然还有一个适配器，并且在每个CardView上都有一个按钮，当我单击该按钮时，我想将相应的对象传递给{ RecyclerView中的{1}}。

FragmentA.java

FragmentB

FragmentB.java

adapter.setOnItemClickListener(new RewardItemAdapter.OnItemClickListener() {
    @Override
    public void onItemClick(int position) {
        //When I click the item, pass theItem to FragmentB
        CustomObject theItem = items.get(position);
    }
});

唯一的问题是我不知道该怎么做，我尝试使用接口，但是无法正确实现，我不确定是否是因为我实例化了片段的新实例。

Answer 1

通过接口执行作业是正确的，但是您必须在onAttached lifeCycle方法中将其绑定到Fragment。

定义一个接口。 OnFragmentInteractionListener.java

public interface OnFragmentInteractionListener {
    // TODO: Update argument type and name
    void onFragmentInteraction(String args);
}

然后通过界面实施您的活动。

    public class MainActivity extends ActionBarActivity implements OnFragmentInteractionListener{

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

        @Override
        onFragmentInteraction(String args){
            **// Made the Change Here**
            // Send Local Broadcast Receiver 
            Intent intent = new Intent("UPDATE_LIST");
            intent.putExtra("TYPE", 0);
            // Change the args to get position or the relevant param
            intent.putExtra("POSITION", selectedPosition);
            LocalBroadcastManager.getInstance(this).sendBroadcast(intent);
        }
   }

在 FragmentA.java 中，

public class FragmentA extends Fragment {
    OnFragmentInteractionListener mCallback;

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

        // This makes sure that the container activity has implemented
        // the callback interface. If not, it throws an exception
        try {
            mCallback = (OnFragmentInteractionListener) context;
        } catch (ClassCastException e) {
            throw new ClassCastException(activity.toString()
                    + " must implement OnFragmentInteractionListener");
        }
    }

    ...

    adapter.setOnItemClickListener(new RewardItemAdapter.OnItemClickListener() 
    {
       @Override
       public void onItemClick(int position) {
       //When I click the item, pass theItem to FragmentB
            CustomObject theItem = items.get(position);
            // Send the selected Item Name to Main Activity through args
            mCallback.onFragmentInteraction(theItem.getName);
       }
    });

}

在您的 FragmentB.java 类上，添加本地广播接收器

公共类FragmentBt扩展Fragment {

    public static Fragment newInstance(){
       ...
    }

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

    ...

    @Override
    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        // Register Local Broadcast Receiver
        LocalBroadcastManager.getInstance(getContext()).registerReceiver(mMessageReceiver, new IntentFilter("UPDATE_LIST"));
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        // Destroy the  Local Broadcast Receiver
        LocalBroadcastManager.getInstance(getContext()).unregisterReceiver(mMessageReceiver);
    }

    // Create Broadcast Receiver instance
    private BroadcastReceiver mMessageReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            if(intent.hasExtra("POSITION")){
                mAdapter.notifyItemChanged(intent.getIntExtra("POSITION", 0));
                // Update Adapter as the requirement
            }
        }
    };

}

希望这会有所帮助。干杯！

Answer 2

您可以通过两种方式实现这一目标：

1）通过片段与活动之间的接口契约

class FragmentA: Fragment() {
    interface SomeInterfaceName {
        fun setSelectedItem(item: SomeItem)
    }
}

class FragmentA: Fragment() {
    interface AnotherInterfaceName {
        fun getSelectedItem(): SomeItem
    }
}

class ContainerActivity: Activity(), AnotherInterfaceName, SomeInterfaceName {
   var someItem: SomeItem? = null

    fun setSelectedItem(item: SomeItem) {
        someItem = item
        // inflate your FragmentB
    }     

    fun getSelectedItem(): SomeItem {
        return someItem;
    }
}

但是我认为最好的解决方案是在这种情况下使用共享的ViewModel。

您可以在“ {在片段之间共享数据”部分here中了解此内容。

从其他片段访问列表

2 个答案: