小编new*_*oid的帖子

我正在尝试AsyncTask在后台执行任务,然后在完成后呈现它,但会发生的事情是在完成之前不会显示任何内容.

我也尝试使用execute并doInBackground调用它,但两者都会导致相同的问题,我必须等待活动开始准备好一切,而不是显示带有加载进度条的页面,然后再添加列表.

码:

private class listTask extends AsyncTask<Void,Void,Void> {
    @Override
    protected Void doInBackground(Void... voids) {
        recyclerview.setAdapter(new ItemAdapter(getInternalFileList()));
        return null;
    }

    @Override
    protected void onPostExecute(Void aVoid) {
        super.onPostExecute(aVoid);
        progressbar.setVisibility(View.GONE);
    }

    List<GalleryItem> getInternalFileList(){
        String path = getActivity().getFilesDir().toString();
        File directory = new File(path);
        File[] files = directory.listFiles();
        List<GalleryItem> galleryItems = new ArrayList<>();

        MainDBRepository repo = new MainDBRepository(getActivity());
        HashMap<String,GalleryItem> itemsMap = repo.getItemsMap();

        for(File file : files) {
            if(itemsMap.containsKey(file.getName()))
                galleryItems.add(itemsMap.get(file.getName()));
        }

        Collections.reverse(galleryItems);

        return galleryItems;
    }

    private class ItemHolder extends RecyclerView.ViewHolder { …

每当我尝试在我的 ubuntu 服务器 18.04 上安装 phpmyadmin 时，我都会收到以下错误

sudo apt install phpmyadmin php-mbstring php-gettext
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to locate package phpmyadmin
E: Unable to locate package php-mbstring
E: Unable to locate package php-gettext

我发现的大多数线程都建议使用 apt 重新更新和升级，但这样做没有任何作用，而且我在第四行也收到了该错误

Err:5 http://ppa.launchpad.net/nijel/phpmyadmin/ubuntu bionic Release
  404  Not Found [IP: 91.189.95.83 80]
Hit:6 http://archive.ubuntu.com/ubuntu bionic-updates InRelease
Hit:7 http://download.webmin.com/download/repository sarge Release
Reading package lists... Done
E: The repository 'http://ppa.launchpad.net/nijel/phpmyadmin/ubuntu bionic Release' does not have a Release file.

有人可以帮忙吗？