1

我在更新 RecyclerView 数据时遇到问题，我猜 notifyDataSetChanged() 有问题，但我不知道是什么问题。RecyclerView 创建后只是空的，没有任何变化。

这是我的代码：

EditFriends2 (once i have it working i erase the "2" ;) )

public class EditFriendsActivty2 extends AppCompatActivity {

private static final String TAG = EditFriendsActivty2.class.getSimpleName();
private ParseUser mCurrentUser;
private ParseRelation<ParseUser> mFriendsRelation;
private List<ParseUser> mFriends;
private List<ParseUser> mUsers;
private FriendsAdapter adapter;

private RecyclerView mRecyclerView;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_edit_friends_activty2);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    mRecyclerView = (RecyclerView) findViewById(R.id.recyclerView);

    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                    .setAction("Action", null).show();
        }
    });
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);

    adapter = new FriendsAdapter(mUsers, mFriends);

    mRecyclerView.setAdapter(adapter);

    RecyclerView.LayoutManager layoutManager = new LinearLayoutManager(EditFriendsActivty2.this);
    mRecyclerView.setLayoutManager(layoutManager);

    mRecyclerView.setHasFixedSize(true);

    showFriendsList();
}

@Override
protected void onResume() {
    super.onResume();
    showFriendsList();
}

private void showFriendsList() {
    mCurrentUser = ParseUser.getCurrentUser();
    mFriendsRelation = mCurrentUser.getRelation(ParseConstants.KEY_FRIENDS_RELATION);

    ParseQuery<ParseUser> query = ParseUser.getQuery();
    query.orderByAscending(ParseConstants.KEY_USERNAME);
    query.setLimit(1000);
    query.findInBackground(new FindCallback<ParseUser>() {
        @Override
        public void done(List<ParseUser> list, ParseException e) {
            if (e == null) {
                // Success
                mUsers = list;
                downloadFriends();
            } else {
                Toast.makeText(EditFriendsActivty2.this, R.string.error_toast, Toast.LENGTH_SHORT).show();
                Log.i(TAG, e.getMessage());
            }
        }
    });
}

private void downloadFriends() {
    mFriendsRelation.getQuery().findInBackground(new FindCallback<ParseUser>() {
        @Override
        public void done(List<ParseUser> list, ParseException e) {
            if (e == null) {
                mFriends = list;

                 // Here i'm updating the RecyclerView, when i have the data about users and friends

                adapter.notifyDataSetChanged();
            } else {
                Log.i(TAG, e.getMessage());
            }
        }
    });
}
}

我的适配器：

public class FriendsAdapter extends RecyclerView.Adapter<FriendsAdapter.FriendsViewHolder> {

private static final String TAG = FriendsAdapter.class.getSimpleName();

private List<ParseUser> mUsers;
private List<ParseUser> mFriends;


public FriendsAdapter(List<ParseUser> users, List<ParseUser> friends){
    mUsers = users;
    mFriends = friends;
}


@Override
public FriendsViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View view = LayoutInflater.from(parent.getContext()).inflate((R.layout.friends_list_item), parent, false);
    FriendsViewHolder viewHolder = new FriendsViewHolder(view);
    return viewHolder;
}

@Override
public void onBindViewHolder(FriendsViewHolder holder, int position) {
    if(mUsers != null) {
        holder.bindFriends(mUsers.get(position));
    }
}

@Override
public int getItemCount() {
    return 0;
}

public class FriendsViewHolder extends RecyclerView.ViewHolder {

    public TextView mNameLabel;
    public CheckBox mCheckBox;

    public FriendsViewHolder(View itemView) {
        super(itemView);

        mNameLabel = (TextView) itemView.findViewById(R.id.nameLabel);
        mCheckBox = (CheckBox) itemView.findViewById(R.id.checkBox);
    }

    public void bindFriends (ParseUser user){
        mNameLabel.setText(user.getUsername());
        mCheckBox.setChecked(false);

        for (ParseUser friend : mFriends){
                if(friend.getObjectId().equals(user.getObjectId())){
                    mCheckBox.setChecked(true);
                    break;
                }
        }
    }
}

}

谁能帮我解决它？提前感谢！

4

2 回答 2

1

最初在创建FriendsAdapteryourmFriends和mUsers列表时是null?

当您收到数据响应时，您正在用新的参考替换您的当前mUsers和mFriends列表。而 RecyclerView 将继续指向旧列表。

解决方案1：

确保mFriends而mUsers不是null开始。

mFriends.addAll(newFriends)然后，您可以mUsers.addAll(newUsers)在收到后添加新朋友和用户。然后执行adapter.notifyDataSetChanged()

解决方案2：

在你添加一个方法FriendsAdapter告诉 RecyclerView 你有一个新列表adapter.showNewFriends(mFriends)。如果您需要这些用户作为另一个参数或另一个方法调用，请在首先获取它们时添加用户。然后在此适配器方法中，您可以调用notifyDataSetChanged().

于 2015-11-09T14:48:26.360 回答
1

问题是您实际上从未更改适配器的列表。查看Activity类中的这一行：

mFriendsRelation.getQuery().findInBackground(new FindCallback<ParseUser>() {
    @Override
    public void done(List<ParseUser> list, ParseException e) {
        if (e == null) {
            mFriends = list;

             // Here i'm updating the RecyclerView, when i have the data about users and friends

            adapter.notifyDataSetChanged();
        } else {
            Log.i(TAG, e.getMessage());
        }
    }
});

您设置的mFriends对象是 Activity 内部的变量，它与 Adapter 内部的不同。我建议在您的适配器中添加这样的方法：

public void swapFriends(List<ParseUser> friends) {
   mFriends = friends;
   notifyDataSetChanged();
}

然后你可以findInBackground()像这样在你的方法中调用它：

mFriendsRelation.getQuery().findInBackground(new FindCallback<ParseUser>() {
    @Override
    public void done(List<ParseUser> list, ParseException e) {
        if (e == null) {
            adapter.swapFriends(list);
        } else {
            Log.i(TAG, e.getMessage());
        }
    }
});

编辑：另一个问题可能在于你的getItemCount()方法。您总是返回 0。您需要返回要显示的朋友数。将其更改为：

@Override
public int getItemCount() {
    return mFriends.size();
}
于 2015-11-09T15:14:29.850 回答