Question

我有需要刷新的列表，我使用PullToRefresh。我曾经使用过Activiti，但现在我需要重写片段中的所有内容。当我使用Activiti一切正常时，但是现在我发现了一个错误，当我复制了我使用相同方法和逻辑的所有内容时，但是发生了一个错误，即nullpointerexception。这是我的片段代码：

private PullToRefreshListView mPullRefreshListView;

public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {        
    View view = inflater.inflate(R.layout.fragment_vk, container, false);
    Map<String, String> networkDetails = getConnectionDetails();
    if (networkDetails.isEmpty()) {
        Toast.makeText(getActivity().getApplicationContext(),
                "Нет интернет подключения!", Toast.LENGTH_LONG).show();
    }
    getActivity().getActionBar().setDisplayShowTitleEnabled(false);
    /** Create an array adapter to populate dropdownlist */
    ArrayAdapter<String> adapter = new ArrayAdapter<String>(
            getActivity().getBaseContext(),
            android.R.layout.simple_spinner_dropdown_item, actions);

    /** Enabling dropdown list navigation for the action bar */
    getActivity().getActionBar().setNavigationMode(ActionBar.NAVIGATION_MODE_LIST);

    /** Defining Navigation listener */
    ActionBar.OnNavigationListener navigationListener = new OnNavigationListener() {

        @Override
        public boolean onNavigationItemSelected(int itemPosition,
                long itemId) {
            switch (itemPosition) {
            case 1:
                Intent intent1 = new Intent(getActivity().getApplicationContext(),
                        KfuNews.class);
                getActivity().finish();
                startActivity(intent1);
                break;
            }
            return false;
        }
    };

    /**
     * Setting dropdown items and item navigation listener for the actionbar
     */
    getActivity().getActionBar().setListNavigationCallbacks(adapter, navigationListener);
    boolean firstrun = getActivity().getSharedPreferences("PREFERENCE", getActivity().MODE_PRIVATE)
            .getBoolean("firstrun", true);

    // Set a listener to be invoked when the list should be refreshed.
    mPullRefreshListView
            .setOnRefreshListener(new OnRefreshListener<ListView>() {
                @Override
                public void onRefresh(
                        PullToRefreshBase<ListView> refreshView) {
                    String label = DateUtils.formatDateTime(
                            getActivity().getApplicationContext(),
                            System.currentTimeMillis(),
                            DateUtils.FORMAT_SHOW_TIME
                                    | DateUtils.FORMAT_SHOW_DATE
                                    | DateUtils.FORMAT_ABBREV_ALL);

                    // Update the LastUpdatedLabel
                    refreshView.getLoadingLayoutProxy()
                            .setLastUpdatedLabel(label);

                    // Do work to refresh the list here.
                    new GetDataTask().execute();
                }
            });

    // Add an end-of-list listener
    mPullRefreshListView
            .setOnLastItemVisibleListener(new OnLastItemVisibleListener() {

                @Override
                public void onLastItemVisible() {
                    Toast.makeText(getActivity().getApplicationContext(), "End of List!",
                            Toast.LENGTH_SHORT).show();
                }
            });
    sp11 = getActivity().getSharedPreferences("VK", 0);
    editor1 = sp11.edit();
    account.restore(getActivity());
    if ((firstrun) || (account.access_token == null)) {
        AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
        builder.setTitle("Авторизация")
                .setMessage(
                        "для просмотра новостей необходимо авторизоваться.")
                .setCancelable(false)
                .setPositiveButton("Авторизоваться",
                        new DialogInterface.OnClickListener() {
                            public void onClick(DialogInterface dialog,
                                    int id) {
                                editor1.putInt("isVk", 1).commit();
                                editor1.apply();
                                startLoginActivity();
                            }
                        })
                .setNegativeButton("Отмена",
                        new DialogInterface.OnClickListener() {
                            public void onClick(DialogInterface dialog,
                                    int id) {
                                dialog.cancel();
                                editor1.putInt("isVk", 0).commit();
                                editor1.apply();
                                Intent intent = new Intent(
                                        getActivity().getApplicationContext(),
                                        KfuNews.class);
                                getActivity().finish();
                                startActivity(intent);
                            }
                        });
        AlertDialog alert = builder.create();
        alert.show();
        // Save the state
        getActivity().getSharedPreferences("PREFERENCE", getActivity().MODE_PRIVATE).edit()
                .putBoolean("firstrun", false).commit();
    }
    if (account.access_token != null) {
        api = new Api(account.access_token, Constants.API_ID);
    }
    Log.d("isChange", isChangedStat + "");
    getWall();
    return view;
}

我在这一行有问题：

mPullRefreshListView
            .setOnRefreshListener(new OnRefreshListener<ListView>() {

我有nullpointerexception，我没有太多时间来解决这个问题，请帮忙。

Answer 1

在片段中启动listview并将listenlay添加到此列表视图中。

Answer 2

您没有初始化 mPullRefreshListView 变量因此nullpointerexception。根据您的代码，您缺少这一行：

mPullRefreshListView = (PullToRefreshListView) view .findViewById(R.id.mPullRefreshListView);

片段中的PullToRefresh

2 个答案: