java - 使用 ViewPager 从 Activity 更改 Fragment TextView

Question

我有一个 Activity ，可以在单击按钮后从 Web API 检索数据并将其保存在自定义统计对象中。在我看来，我有一个带有 ViewPager 的 TabLayout。问题是，在 Activity 检索所有数据后，我无法更改 Fragment 中的 TextView，我总是收到 NullPointerException。

我尝试了很多方法，但似乎都不起作用，我不知道该怎么办。

这是我的 Activity :

public class StatsActivity extends AppCompatActivity {

    public TextView textStats, responseView;
    public EditText usuario;
    public ProgressBar progressBar;
    public ImageButton buscar;
    public TabLayout tabLayout;
    public TabItem tabSolo, tabDuo, tabSquad;
    public ViewPager viewPager;

    String idUsuario, user;
    Stats soloStats = new Stats();
    Stats duoStats = new Stats();
    Stats squadStats = new Stats();
    Typeface TF;
    PageAdapter pageAdapter;


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

        textStats = findViewById(R.id.textStats);
        progressBar = findViewById(R.id.progressBar);
        responseView = findViewById(R.id.responseView);
        usuario = findViewById(R.id.editText);
        buscar = findViewById(R.id.searchButton);
        tabLayout = findViewById(R.id.tabs);
        tabSolo = findViewById(R.id.tabsolo);
        tabDuo = findViewById(R.id.tabduo);
        tabSquad = findViewById(R.id.tabsquad);
        viewPager = findViewById(R.id.pager);

        TF = Typeface.createFromAsset(getAssets(), "font/BurbankBigCondensed-Bold.ttf");

        pageAdapter = new PageAdapter(getSupportFragmentManager(), tabLayout.getTabCount());
        viewPager.setAdapter(pageAdapter);
        viewPager.addOnPageChangeListener(new TabLayout.TabLayoutOnPageChangeListener(tabLayout));
        viewPager.setVisibility(View.INVISIBLE);
        setCustomFont();

        LinearLayout tabStrip = ((LinearLayout) tabLayout.getChildAt(0));
        for(int i = 0; i < tabStrip.getChildCount(); i++) {
            tabStrip.getChildAt(i).setOnTouchListener(new View.OnTouchListener() {
                @Override
                public boolean onTouch(View v, MotionEvent event) {
                    return true;
                }
            });
        }

        tabLayout.setVisibility(View.INVISIBLE);

        responseView.setText("");
        responseView.setMovementMethod(new ScrollingMovementMethod());

        textStats.setTypeface(TF);
        responseView.setTypeface(TF);

        buscar.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                user = usuario.getText().toString().trim();
                new getPlayerId().execute();
            }
        });

    }

    class getPlayerId extends AsyncTask<Void, Void, String> {

        private Exception exception;

        protected void onPreExecute() {
            progressBar.setVisibility(View.VISIBLE);
            responseView.setText("");
        }

        protected String doInBackground(Void... urls) {

            user = user.trim();

            try {
                // getting data

                    return stringBuilder.toString();
                }
                finally{
                    urlConnection.disconnect();
                }
            }
            catch(Exception e) {
                Log.e("ERROR", e.getMessage(), e);
                return null;
            }
        }

        protected void onPostExecute(String response) {
            if(response == null) {
                response = "THERE WAS AN ERROR";
            }
            Log.i("INFO", response);

            try {
                JSONObject object = (JSONObject) new JSONTokener(response).nextValue();

                //Parsing JSON and setting soloStats

            } catch (JSONException e) {
                e.printStackTrace();
            }

            //HERE IS WHERE I WANT TO CHANGE MY FRAGMENT TEXTVIEW

            //SoloFragment solo = (SoloFragment) pageAdapter.getItem(0);
            //solo.getStats(soloStats);
        }
    }
}

我的 fragment 代码:

public class SoloFragment extends Fragment {

    TextView textVictorias, textTop2, textTop3, textPartidas, textKills, textPuntos, textMinutos, textJugadores;

    public SoloFragment() {
        // Required empty public constructor
    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment

        View v = inflater.inflate(R.layout.fragment_solo, container, false);

        textVictorias = v.findViewById(R.id.textVictorias);
        textTop2 = v.findViewById(R.id.textTop2);
        textTop3 = v.findViewById(R.id.textTop3);
        textPartidas = v.findViewById(R.id.textPartidas);
        textKills = v.findViewById(R.id.textKills);
        textPuntos = v.findViewById(R.id.textPuntos);
        textMinutos = v.findViewById(R.id.textMinutos);
        textJugadores = v.findViewById(R.id.textJugadores);

        return v;
    }

    public void setStats(Stats stats){

        textVictorias.setText(stats.getTop1());
        textTop2.setText(stats.getTop2());
        textTop3.setText(stats.getTop3());
        textPartidas.setText(stats.getPartidas());
        textKills.setText(stats.getKills());
        textPuntos.setText(stats.getPuntos());
        textMinutos.setText(stats.getMinutos());
        textJugadores.setText(stats.getJugadores());

    }

}

我总是在 setStats 中的 setText 上得到 NPE，我不知道如何解决这个问题，希望有人能帮助我!谢谢!

Answer 1

在 onPostExecute 方法中使用它

      //HERE IS WHERE I WANT TO CHANGE MY FRAGMENT TEXTVIEW        
      if (pageAdapter.getFragment() != null) {
          pageAdapter.getFragment().getStats(soloStats);
      }