ListView fehler: Attempt to invoke interface method 'int java.util.List.size()' on a null object reference

[wer112]

Ich habe damals in mein App Store eine Listview gemacht(mehrere) die alle bisher funktioniert hat.
Ich habe das exakt nachgemacht, wie früher, leider bekomme ich diese Fehlermeldung:

java.lang.NullPointerException: Attempt to invoke interface method 'int java.util.List.size()' on a null object reference
                                                                                                        at android.widget.ArrayAdapter.getCount(ArrayAdapter.java:389)
                                                                                                        at android.widget.ListView.setAdapter(ListView.java:612)
                                                                                                        at com.andrealfredklug.klugstore.Konsole.App_spenden$1.onResponse(App_spenden.java:184)
                                                                                                        at com.andrealfredklug.klugstore.Konsole.App_spenden$1.onResponse(App_spenden.java:84)
                                                                                                        at com.android.volley.toolbox.JsonRequest.deliverResponse(JsonRequest.java:100)
                                                                                                        at com.android.volley.ExecutorDelivery$ResponseDeliveryRunnable.run(ExecutorDelivery.java:102)
                                                                                                        at android.os.Handler.handleCallback(Handler.java:938)
                                                                                                        at android.os.Handler.dispatchMessage(Handler.java:99)
                                                                                                        at android.os.Looper.loopOnce(Looper.java:226)
                                                                                                        at android.os.Looper.loop(Looper.java:313)
                                                                                                        at android.app.ActivityThread.main(ActivityThread.java:8751)
                                                                                                        at java.lang.reflect.Method.invoke(Native Method)
                                                                                                        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:571)
                                                                                                        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1135)

Die TEST Json und die ArrayList klappen laut Log.e():

{"status":"es gibt Apps","AppAnzahl":2,"Apps":"{\"app_name\":[\"CoundownWlanApp\",\"Navigator\"],\"package\":[\"com.andrealfredklug.countdownwlanapp\",\"com.navigator\"],\"utc\":[\"02.10.2024\",\"01.10.2024\"]}"}
2024-10-04 17:40:34.990 14738-14738 App spenden             com.andrealfredklug.klugstore        E  [CoundownWlanApp, Navigator]
2024-10-04 17:40:34.990 14738-14738 App spenden             com.andrealfredklug.klugstore        E  [com.andrealfredklug.countdownwlanapp, com.navigator]
2024-10-04 17:40:34.990 14738-14738 App spenden             com.andrealfredklug.klugstore        E  [02.10.2024, 01.10.2024]

Sobald ich den listview.setadapter mache crascht die Listview.

Meine Klasse:

package com.andrealfredklug.klugstore.Konsole;

import android.app.Fragment;
import android.graphics.drawable.ColorDrawable;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;

import androidx.activity.EdgeToEdge;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AlertDialog;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.graphics.Insets;
import androidx.core.view.ViewCompat;
import androidx.core.view.WindowInsetsCompat;

import com.andrealfredklug.klugstore.ALoadingDialog;
import com.andrealfredklug.klugstore.Adapter.App_spenden_Adapter;
import com.andrealfredklug.klugstore.R;
import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.JsonObjectRequest;
import com.android.volley.toolbox.Volley;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import java.util.ArrayList;

public class App_spenden extends Fragment {

    TextView keineApps;

    public ALoadingDialog aLoadingDialog;

    final String TAG = "App spenden";

    App_spenden_Adapter adapter;
    ListView listView;

    ArrayList appName, appPackage, appUtc;

    String abruf_url = "https://www.klug-aug.de/projekte/klugstore/php/android-scripte/entwicklerPHP/console/app_spenden_information.php";

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) {
        View app_spenden = inflater.inflate(R.layout.activity_app_spenden, null);
        return app_spenden;
    }

    @Override
    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {

        adapter = new App_spenden_Adapter(getActivity(), appName, appPackage, appUtc);
        listView = (ListView)view.findViewById(R.id.as_listview);

        aLoadingDialog = new ALoadingDialog(getActivity());
        keineApps = (TextView)view.findViewById(R.id.as_keine_apps_textView);
        keineApps.setVisibility(View.GONE);

        appName = new ArrayList<String>();
        appPackage = new ArrayList<String>();
        appUtc = new ArrayList<String>();


        AppsImport();
    }

    private void AppsImport() {
    aLoadingDialog.show();

        RequestQueue queue = Volley.newRequestQueue(getActivity());

        JsonObjectRequest jsonObjectRequest = new JsonObjectRequest(Request.Method.POST, abruf_url, null, new Response.Listener<JSONObject>() {
            @Override
            public void onResponse(JSONObject response) {
            Log.e(TAG, "" + response.toString());

            String json = response.toString();
            try {
                JSONObject jsonObject = new JSONObject(json);

                if (jsonObject.getString("status").equals("Session fehler")){
                    AlertDialog.Builder builder = new AlertDialog.Builder(getActivity(), R.style.AlertDialogTheme);
                    View view = LayoutInflater.from(getActivity()).inflate(R.layout.layout_error_dialog, getView().findViewById(R.id.layoutDialogContainer));


                    builder.setView(view);
                    ((TextView) view.findViewById(R.id.textTitle)).setText("Session");
                    ((TextView) view.findViewById(R.id.textView_error)).setText("Bitte melden Sie sich erneut an oder wenden Sie sich an den Support: support@klug-aug.de\n\n");
                    ((Button) view.findViewById(R.id.buttonAction)).setText(getString(R.string.okay));
                    ((ImageView) view.findViewById(R.id.image_error)).setImageResource(R.drawable.ic_error);

                    final AlertDialog alertDialog = builder.create();

                    view.findViewById(R.id.buttonAction).setOnClickListener(new View.OnClickListener() {
                        @Override
                        public void onClick(View v) {
                            alertDialog.dismiss();
                            aLoadingDialog.dismiss();
                        }
                    });

                    if (alertDialog.getWindow() != null) {
                        alertDialog.getWindow().setBackgroundDrawable(new ColorDrawable(0));
                    }


                    alertDialog.show();

                }else if(jsonObject.getString("status").equals("Du bist nicht angemeldet.")){
                    AlertDialog.Builder builder = new AlertDialog.Builder(getActivity(), R.style.AlertDialogTheme);
                    View view = LayoutInflater.from(getActivity()).inflate(R.layout.layout_error_dialog, getView().findViewById(R.id.layoutDialogContainer));


                    builder.setView(view);
                    ((TextView) view.findViewById(R.id.textTitle)).setText("Abgemeldet");
                    ((TextView) view.findViewById(R.id.textView_error)).setText("Du bist abgemeldet. Bitte melde dich erneut an.\n");
                    ((Button) view.findViewById(R.id.buttonAction)).setText(getString(R.string.okay));
                    ((ImageView) view.findViewById(R.id.image_error)).setImageResource(R.drawable.ic_error);

                    final AlertDialog alertDialog = builder.create();

                    view.findViewById(R.id.buttonAction).setOnClickListener(new View.OnClickListener() {
                        @Override
                        public void onClick(View v) {
                            alertDialog.dismiss();
                            aLoadingDialog.dismiss();
                        }
                    });

                    if (alertDialog.getWindow() != null) {
                        alertDialog.getWindow().setBackgroundDrawable(new ColorDrawable(0));
                    }


                    alertDialog.show();
                } else if (jsonObject.getString("status").equals("keine Apps")) {
                    keineApps.setVisibility(View.VISIBLE);
                    aLoadingDialog.dismiss();

                } else if (jsonObject.getString("status").equals("es gibt Apps")) {
                    aLoadingDialog.dismiss();

                    JSONObject jsonApps = new JSONObject(jsonObject.getString("Apps"));

                    String anzahl = response.getString("AppAnzahl").trim();
                    Integer anzahlInt = Integer.parseInt(anzahl);

                    if (anzahlInt == 1){
                        String appN, appP, appU;
                        appN = jsonApps.getString("app_name");
                        appP = jsonApps.getString("package");
                        appU = jsonApps.getString("utc");

                        appName.add(appN);
                        appPackage.add(appP);
                        appUtc.add(appU);

                        listView.setVisibility(View.VISIBLE);
                        listView.setAdapter(adapter);

                    } else if (anzahlInt > 1) {

                        JSONArray name = jsonApps.getJSONArray("app_name");
                        JSONArray pack = jsonApps.getJSONArray("package");
                        JSONArray utc = jsonApps.getJSONArray("utc");

                        for(int i = 0; i < anzahlInt; i++){
                         appName.add(name.get(i));
                         appPackage.add(pack.get(i));
                         appUtc.add(utc.get(i));
                        }

                        Log.e(TAG, appName.toString());
                        Log.e(TAG, appPackage.toString());
                        Log.e(TAG, appUtc.toString());
                        listView.setVisibility(View.VISIBLE);
                        listView.setAdapter(adapter);
                    }


                }

            } catch (JSONException e) {
                throw new RuntimeException(e);
            }


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

            }
        });

        queue.add(jsonObjectRequest);
    }
}

Mein Adapter:

package com.andrealfredklug.klugstore.Adapter;

import android.app.Activity;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;

import com.andrealfredklug.klugstore.R;

import java.util.ArrayList;

public class App_spenden_Adapter extends ArrayAdapter<String> {
    private final Activity context;
    private ArrayList appname = new ArrayList<String>();
    private ArrayList packagename = new ArrayList<String>();
    private ArrayList utc = new ArrayList<String>();

    public App_spenden_Adapter(Activity context,  ArrayList<String> appname, ArrayList<String> packagename, ArrayList<String> utc){
        super(context, R.layout.app_spenden_listview, packagename);

        this.context = context;
        this.appname = appname;
        this.packagename = packagename;
        this.utc = utc;
    }

    @NonNull
    @Override
    public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
        LayoutInflater inflater=context.getLayoutInflater();
        View rowView=inflater.inflate(R.layout.app_spenden_listview, null,true);

        TextView appnameText = (TextView) rowView.findViewById(R.id.as_appname_textView);
        TextView apppackageText = (TextView) rowView.findViewById(R.id.as_list_package_textView);
        TextView apputcText = (TextView) rowView.findViewById(R.id.as_list_utc_textView);

        appnameText.setText(appname.get(position).toString());
        apppackageText.setText(packagename.get(position).toString());
        apputcText.setText(utc.get(position).toString());
        return rowView;
    }
}

Ich weiß nicht woran das liegt, das es diesmal nicht klappt und sonst immer klappt.

Ich bedanke mich mal bei euch für eure Hilfe 😉

 

[Robert Zenz]

189:                        listView.setAdapter(adapter);

Augenscheinlich ist adapter null. Wenn ich raten muesste (und das muss ich weil ich den Code nicht so genau gelesen habe) wuerde ich sagen das onViewCreated erst aufgerufen wird nachdem die Anfrage durchgefuehrt wurde.

 

[wer112]

189:                        listView.setAdapter(adapter);

Augenscheinlich ist adapter null. Wenn ich raten muesste (und das muss ich weil ich den Code nicht so genau gelesen habe) wuerde ich sagen das onViewCreated erst aufgerufen wird nachdem die Anfrage durchgefuehrt wurde.

Ne das Problem habe ich gelöst, musste den Adapter erst deklarieren nachdem der AppsImport erfolgt ist.