RecyclerView 未加载

Question

I have created a Recycler view that is supposed to be created when the activity is created. Currently, when I click a button on my MainActivity, an intent launches the ListActivity which has my recyclerview but it doesn't load. I have used toast message to confirm that each method is getting called, and that I am getting the correct data from the API. If I reset the activity using the restart activity option in Android Studio the Recycler shows up and functions correctly. I don't know what I'm doing wrong.

Here is my ListActivity:

    private RecyclerView myrecyclerview;
    private RecyclerView.Adapter myadapter;
    private RecyclerView.LayoutManager mylayoutmanager;
    static RequestQueue listqueue;
    static final private String url = "https://swapi.dev/api/people/";

    static ArrayList<RecyclerItem> list = new ArrayList<>();


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_list);
        getSupportActionBar().hide();
        listqueue = Volley.newRequestQueue(this);

        myrecyclerview = findViewById(R.id.characterlist);
        

        myadapter = new MyAdapter(list, this);
        myrecyclerview.setAdapter(myadapter);
        myrecyclerview.setHasFixedSize(true);
        mylayoutmanager = new LinearLayoutManager(getApplicationContext());
        myrecyclerview.setLayoutManager(mylayoutmanager);
        parseJsonData();
    }

    public void parseJsonData(){
    JsonObjectRequest request = new JsonObjectRequest(
            Request.Method.GET,
            url, null,
            new Response.Listener<JSONObject>() {
                @Override
                public void onResponse(JSONObject response) {
                    Toast.makeText(getApplicationContext(), response.toString(), Toast.LENGTH_SHORT).show();

                    try {
                        JSONArray jsonarray = response.getJSONArray("results");
                        for (int i = 0; i < jsonarray.length(); i++) {
                            JSONObject jsonobject = jsonarray.getJSONObject(i);

                            String name = jsonobject.getString("name");
                            String height = jsonobject.getString("height");
                            String mass = jsonobject.getString("mass");
                            String eyecolor = jsonobject.getString("eye_color");
                            String birthyear = jsonobject.getString("birth_year");

                            //list.add(new RecyclerItem("darth vader", "200", "128", "1950", "red"));
                            list.add(new RecyclerItem(name, "Height: " + height, "Mass: " + mass, "Birth Year: " + birthyear, eyecolor));
                        }
                    } catch (JSONException e) {
                        e.printStackTrace();
                    }

                }

            }, new Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError error) {
            error.printStackTrace();
        }
    });

        listqueue.add(request);

    }


    @Override
    public void onCharacterClick(int position) {
        String color = list.get(position).getEyecolor();
        Toast.makeText(getApplicationContext(), color, Toast.LENGTH_SHORT).show();
    }

} ```

Like I mentioned, once I reload the activity, it works correctly. But I want the recycler view to show when I navigate to the activity.

Answer 1

The problem is that the first time that the activity is create, list is empty and parseJsonData() is running on the background filling that list. Once you reload the activiy, the list and adapter are filled therefore when you call

myadapter = new MyAdapter(list, this);
myrecyclerview.setAdapter(myadapter);
myrecyclerview.setHasFixedSize(true);
mylayoutmanager = new LinearLayoutManager(getApplicationContext());
myrecyclerview.setLayoutManager(mylayoutmanager);

the recycler view is show. Try to do this on your parseJsonData() ; after the loop ends, then create the adapter and show the rv

for (int i = 0; i < jsonarray.length(); i++) {
   JSONObject jsonobject = jsonarray.getJSONObject(i);
   ....
}

myadapter = new MyAdapter(list, this);
....
myrecyclerview.setLayoutManager(mylayoutmanager);

Answer 2

I hope it help for u

Creat a List

private List< TipsList > tipsLists = new ArrayList<>();

SET UP RECYCLERVIEW LIKE THIS

RecyclerView tipsRv = findViewById(R.id.tips_rv);
    TipsAdapter adapter = new TipsAdapter(tipsLists, this);
    tipsRv.setAdapter(adapter);
    tipsRv.setHasFixedSize(true);
    tipsRv.setLayoutManager(new LinearLayoutManager(this));

getDATA

 public void getWallis() {
    String myJSONStr = method.loadJSON();

    try {
        JSONObject ROOT_OBJ = new JSONObject(myJSONStr);
        JSONArray MAIN_ARRAY = ROOT_OBJ.getJSONArray("ff_api");
        JSONObject TIPS_OBJ = MAIN_ARRAY.getJSONObject(3);
        JSONArray TIPS_ARRAY = TIPS_OBJ.getJSONArray("Tips");

        for (int i = 0; i < TIPS_ARRAY.length(); i++) {
            TipsList tipsList = new TipsList();
            JSONObject jsonObject = TIPS_ARRAY.getJSONObject(i);
            tipsList.setId(jsonObject.getInt("id"));
            tipsList.setTipsTitle(jsonObject.getString("tipsTitle"));
            tipsList.setTipsDec(jsonObject.getString("tipsDec"));
            tipsLists.add(tipsList);
        }

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