如何指定要在列表中<parseObject>添加的解析对象

Question

我正在尝试根据当前用户的用户名在我的列表中添加一些特定的 ParseObject。但是这段代码只在NullPointerException中结束了：

query.findInBackground（new FindCallback（）

mStatus.add（status.get（i））;

有人请帮我解决这个问题。谢谢。

@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View view = null;
    view = inflater.inflate(R.layout.update_status, container, false);
    ParseUser currentUser = ParseUser.getCurrentUser();
    final String strCurrentUsername = currentUser.getUsername();
    if (currentUser != null) {
        //try
        final ParseQuery<ParseObject> query = new ParseQuery<ParseObject>("Status");
        query.orderByDescending("createdAt");
        query.findInBackground(new FindCallback<ParseObject>() {
            @Override
            public void done(final List<ParseObject> status, ParseException e) {
                if(e == null){
                    //success
                    for(int i = 0; i <status.size();i++){
                        String usernow = status.get(i).getString("user");
                        if(usernow.equals(strCurrentUsername)){
                            Toast.makeText(getActivity(), "num"+i, Toast.LENGTH_SHORT).show();
                            mStatus.add(status.get(i));
                        }
                        else i++;
                    }
                    //mStatus = status;
                    StatusAdapter statusAdapter = new StatusAdapter( getListView().getContext(), mStatus);
                    setListAdapter(statusAdapter);
                }else{
                    //there was a problem
                }
            }
        });

    } else {
        Intent intent = new Intent(getActivity(), FirstActivity.class);
        startActivity(intent);
    }
    return view;
}

Answer 1

mStatus 是否启动？ mStatus 是类字段吗？我不确定您从哪里得到空异常，但我测试了您的代码，这对我有用，其中用户是我的解析数据库中的一列，其值是一个字符串：

 ParseUser currentUser = ParseUser.getCurrentUser();
    final String strCurrentUsername = currentUser.getUsername();
    if (currentUser != null) {
        //try
        final ParseQuery<ParseObject> query = new ParseQuery<ParseObject>("Status");
        query.orderByDescending("createdAt");
        query.findInBackground(new FindCallback<ParseObject>() {
            @Override
            public void done(final List<ParseObject> status, ParseException e) {
                if (e == null) {
                    ArrayList<ParseObject> mStatus = new ArrayList<ParseObject>();
                    //success
                    for (int i = 0; i < status.size(); i++) {
                        String usernow = status.get(i).getString("user");
                        if (usernow.equals(strCurrentUsername)) {
                            mStatus.add(status.get(i));
                        } else i++;
                    }

                } else {
                    //there was a problem
                }
            }
        });

    } else {
    }