RecyclerView.Adapter onClick ClassCastException

Question

我试图在Fragment内加载Activity，我可以加载这些项目。现在，我想要做的是单击列表中的项目并将其传递给DetailsView.class，Fragment将收到捆绑数据java.lang.ClassCastException: com.test.example.LoadAFragment cannot be cast to com.test.example.MainActivity at com.test.example.controller.DetailsView.onCreateView(DetailsView.java:178) 。但每次我点击该项目我总是会收到错误。以下是我得到的logcat错误

Logcat错误

MainActivity activity = ((MainActivity) getActivity());

行java：178

public class LoadAFragment extends Activity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.load_layout);
        FragmentManager fragmentManager = getFragmentManager();
        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
        MyFragment myFragment = new MyFragment();
        fragmentTransaction.add(R.id.frame_container, myFragment);
        fragmentTransaction.commit();
    }
}

LoadAFragment.class

public class MyFragmentAdapter extends RecyclerView.Adapter <RecyclerView.ViewHolder> {

    private List<ListModel> list;
    private Context mContext = null;
    private DetailsView detailsView;

    public MyFragmentAdapter(Context context, List<ListModel> list) {
        mContext = context;
        this.list = list;
    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item, parent, false);
        return new MyViewHolder(view);
    }

    @Override
    public void onBindViewHolder(final RecyclerView.ViewHolder holder, int position) {
        final ListModel list = list.get(holder.getAdapterPosition());
        String mID = list.getID();
        final int id = Integer.valueOf(mID );
        ((MyViewHolder) holder).title.setText(list.getTitle());
        ((MyViewHolder) holder).caption.setText(list.getCaption());
        ((MyViewHolder) holder).itemView.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                FragmentManager manager = ((Activity) mContext).getFragmentManager();
                FragmentTransaction transaction = manager.beginTransaction();
                Bundle bundle = new Bundle();
                bundle.putInt("id", id);
                detailsView = new DetailsView ();
                detailsView.setTitle(title);
                detailsView.setArguments(bundle);
                transaction.replace(R.id.frame_container, detailsView);
                transaction.addToBackStack("list");
                transaction.commit();
            }
        });
    }

    @Override
    public int getItemCount() {
        return (list != null? list.size():0);
    }

    private class MyViewHolder extends RecyclerView.ViewHolder {

        public TextView title;
        public TextView caption;

        MyViewHolder(View itemView) {
            super(itemView);
            title = (TextView) itemView.findViewById(R.id.title);
            caption = (TextView) itemView.findViewById(R.id.caption );
        }
    }
}

RecyclerView适配器

public class MyFragment extends Fragment{

    List<ListModel> list;
    RecyclerView mRecyclerView;
    MyFragmentAdapter myFragmentAdapter;
    ListDb listDb;

    public MyFragment() {}

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        super.onCreateView(inflater, container, savedInstanceState);

        View rootView = inflater.inflate(R.layout.fragment, container, false);

        mRecyclerView = (RecyclerView) rootView.findViewById(R.id.recyclerview);

        listDb = new ListDb(getActivity());
        list = listDb.getList();
        myFragmentAdapter = new MyFragmentAdapter (getActivity(), list);
        mRecyclerView.setAdapter(myFragmentAdapter);

        return rootView;
    }
}

MyFragment.class

public class DetailsView extends Fragment{
     private MainActivity activity;
Bundle b;

public DetailsView() {}

 @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (savedInstanceState != null)
            b = savedInstanceState.getBundle("save");
      }

 @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        super.onCreateView(inflater, container, savedInstanceState);
        activity = ((MainActivity) getActivity());
        return rootView;
    }

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

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        if (b != null) {
            setTitle(b.getString("title"));
            id = b.getInt("id");
        }
        if (b != this.getArguments().getInt("id")) {
            b = this.getArguments().getInt("id");
            //get data from id
        }
    }
}

DetailsView.class

{{1}}

Answer 1

在DetailsView.java中将getActivity（）强制转换为'LoadAFragment'而不是'MainActivity'。这样：

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    super.onCreateView(inflater, container, savedInstanceState);
    activity = ((LoadAFragment) getActivity());
    return rootView;
}

Answer 2

最好和最干净的解决方案是将侦听器传递给适配器。

qRegisterMetaType

让Fragment实现监听器并创建新的适配器。

{
    bool const _ = []{
        qRegisterMetaType<QItemSelection>();
        qRegisterMetaType<QItemSelectionModel::SelectionFlags>();
        return true;
    }();
}

Answer 3

尝试这种方式在MainActivity

中引用DetailViewFragment

private MainActivity parent_activity;

 @Override
public void onAttach(Activity activity)
{
    parent_activity = (MainActivity.class.isAssignableFrom(activity
            .getClass())) ? (MainActivity) activity : null;
    super.onAttach(activity);
}

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

现在使用参考：

 if(parent_activity!=null)
{
   parent_activity.someMethod();
}