Java 从类方法显示进度对话框

在我的主要活动中，我使用从服务器下载数据的方法初始化了一个类

我想在下载之前显示一个进度对话框。但它不会显示“进度”对话框

我的主要活动：

public class MainActivity extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener{

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
        drawer.setDrawerListener(toggle);
        toggle.syncState();

        NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
        navigationView.setNavigationItemSelectedListener(this);

        setFragmentManager(new MainActivityFragment());

        Updater updater = new Updater(this,(ViewGroup) findViewById(R.id.fragment));
        updater.check();
    }

    public void setFragmentManager(Fragment fragment){
        FragmentManager fragmentManager = getSupportFragmentManager();
        FragmentTransaction fragmentTransaction  = fragmentManager.beginTransaction();
        fragmentTransaction.replace(R.id.fragment, fragment);
        fragmentTransaction.addToBackStack(null);
        fragmentTransaction.commit();
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        switch (id){
            case R.id.action_settings:
                return true;
            case R.id.medi_calc_item:
                setFragmentManager(new MediCalcFragment());
            default:
                return super.onOptionsItemSelected(item);
        }
    }

    @SuppressWarnings("StatementWithEmptyBody")
    @Override
    public boolean onNavigationItemSelected(MenuItem item) {
        // Handle navigation view item clicks here.
        int id = item.getItemId();
        switch (id){
            case R.id.nav_start:
                setFragmentManager(new MainActivityFragment());
                break;
            case R.id.nav_medis:
                setFragmentManager(new MediAbcFragment());
                break;
            case R.id.nav_bos:
                setFragmentManager(new BosAbcFragment());
                break;
            default:
                break;
        }

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        drawer.closeDrawer(GravityCompat.START);
        return true;
    }

    @Override
    public void onBackPressed() {
        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        if (drawer.isDrawerOpen(GravityCompat.START)) {
            drawer.closeDrawer(GravityCompat.START);
        } else {
            super.onBackPressed();
        }
    }
}

我的班级：

public class Updater {
    private Context context;
    private ViewGroup viewGroup;
    private VersionsDAO versionsDAO;
    private MediDAO mediDAO;
    private RegioDAO regioDAO;
    private HashMap<String,Integer> onlineVersions;
    private HashMap<String,Integer> versions;
    private ProgressDialog progressDialog;

    public Updater(Context context, ViewGroup viewGroup) {
        this.context = context;
        this.versionsDAO = new VersionsDAO(context);
        this.mediDAO = new MediDAO(context);
        this.viewGroup = viewGroup;
        this.onlineVersions = new HashMap<>();
        this.regioDAO = new RegioDAO(context);
        this.progressDialog = new ProgressDialog(context);
    }

    public void check(){
progressDialog.setMessage(context.getString(R.string.update_cities));
            progressDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);
            progressDialog.setIndeterminate(true);
            progressDialog.show();
            RequestQueue queue = Volley.newRequestQueue(this.context);
            String url ="http://resper.de/resperApi.php?cmd=deStadt";
            StringRequest stringRequest = new StringRequest(Request.Method.GET, url,
                    new Response.Listener<String>() {
                        @Override
                        public void onResponse(String response) {
                            try {
                                JSONArray jArray = new JSONArray(response);
                                for(int i = 0; i < jArray.length(); i++){
                                    JSONObject jObject = jArray.getJSONObject(i);
                                    regioDAO.insertDeStadt(jObject.getInt("id"), jObject.getString("name"), jObject.getInt("bl"), jObject.getInt("rb"), jObject.getInt("kreis"), jObject.getInt("lk"));
                                }
                                versionsDAO.updateVersion("deStadt", onlineVersions.get("deStadt"));
                                progressDialog.cancel();

                            }catch (JSONException e) {
                                e.printStackTrace();
                            }
                        }
                    }, new Response.ErrorListener() {
                @Override
                public void onErrorResponse(VolleyError error) {
                    serverNotAvailable();
                }
            });
            queue.add(stringRequest);
            progressDialog.cancel();
    }
}

公共类更新程序{
私人语境；
私有视图组视图组；
私有版本dao版本dao；
私人医疗岛；
私人区道区道；
私有HashMap在线版本；
私有HashMap版本；
私有进程对话；
公共更新程序（上下文、视图组、视图组）{
this.context=上下文；
this.versionsDAO=新的versionsDAO（上下文）；
this.mediDAO=新的mediDAO（上下文）；
this.viewGroup=viewGroup；
this.onlineVersions=新HashMap（）；
this.regioDAO=新regioDAO（上下文）；
this.progressDialog=新建progressDialog（上下文）；
}
公共作废检查（）{
progressDialog.setMessage（context.getString（R.string.update_cities））；
progressDialog.setProgressStyle（progressDialog.STYLE_微调器）；
progressDialog.setUndeterminate（true）；
progressDialog.show（）；
RequestQueue=Volley.newRequestQueue（this.context）；
字符串url=”http://resper.de/resperApi.php?cmd=deStadt";
StringRequest StringRequest=新的StringRequest（Request.Method.GET，url，
新的Response.Listener（）{
@凌驾
公共void onResponse（字符串响应）{
试一试{
JSONArray jArray=新JSONArray（响应）；
for（int i=0；i

删除

progressDialog.cancel（）从最后一行开始。即在
queue.add（stringRequest）之后并重试。
删除
progressDialog.cancel（）从最后一行开始。即在
queue.add（stringRequest）之后然后再试一次Md Sufi Khan，就是这样。欢迎。如果答案对你有帮助，请接受。快乐编码：）