Question

我使用Volley从phpmysql数据库中获取数据。现在，每当我单击按钮显示对话框时，我的应用程序都会崩溃并显示以下错误：

有什么问题？

这是我的代码：

public class SetTask extends Fragment {

ListView lv_task_chooser;
ArrayList<SetTaskModel> setTaskModelArrayList;
private SetTaskAdapter setTaskAdapter;
ArrayAdapter<String> scAdapter;
String url, category;
RequestQueue queue_fetch, queue_fetch1;
ConnectivityManager connMgr;
NetworkInfo networkInfo;
Context ctx;
int cat_id;
LinearLayout taskLayout;
private String[] array;
private int[] sub_cat_id;
JSONArray jsonArray, jsonArray1;

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

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    View rootView = inflater.inflate(R.layout.fragment_set_task, container, false);

    ctx = getContext();

    lv_task_chooser = (ListView)rootView.findViewById(R.id.lv_task_chooser);
    taskLayout = (LinearLayout)rootView.findViewById(R.id.taskLayout);

    queue_fetch = Volley.newRequestQueue(ctx);
    queue_fetch1 = Volley.newRequestQueue(ctx);

    setTaskModelArrayList = new ArrayList<>();

    fetchDB();

    Log.i("pointafterfetch", "reached");
    Log.i("numberofarrayentries", String.valueOf(setTaskModelArrayList.size()));

    for (int i = 0; i < setTaskModelArrayList.size(); i++){
        Log.i("arrayentriesfetch", setTaskModelArrayList.get(i).toString());
    }

    //setTaskAdapter = new SetTaskAdapter(setTaskModelArrayList, ctx);
    //lv_task_chooser.setAdapter(setTaskAdapter);

    /*lv_task_chooser.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            populateSpinner(position);
        }
    });*/

    return rootView;
}

private void fetchDB(){

    url = "http://nmstech.in/coach/categorys.php";

    connMgr = (ConnectivityManager) ctx.getSystemService(Context.CONNECTIVITY_SERVICE);
    networkInfo = connMgr.getActiveNetworkInfo();

    if (!(networkInfo != null && networkInfo.isConnected())) {
        final AlertDialog.Builder builder1 = new AlertDialog.Builder(ctx);
        builder1.setTitle(getString(R.string.network_no_t));
        builder1.setMessage(getString(R.string.network_no_m));
        builder1.setPositiveButton("OK", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                dialog.dismiss();
            }
        });

        builder1.create().show();
    }

    else{

        StringRequest strreq_fetch = new StringRequest(Request.Method.GET, url,
                new Response.Listener<String>() {

                    @Override
                    public void onResponse(String Response) {
                        try {
                            jsonArray = new JSONArray(Response);

                            for(int i = 0; i < jsonArray.length(); i++){

                                setTaskModelArrayList.add(new SetTaskModel(jsonArray.getJSONObject(i)
                                        .getString("cat_name")));
                                Log.i("arraylistentries", setTaskModelArrayList.get(i).getCategory());
                                Log.i("noentries", String.valueOf(setTaskModelArrayList.size()));

                                setTaskAdapter = new SetTaskAdapter(setTaskModelArrayList, ctx);
                                lv_task_chooser.setAdapter(setTaskAdapter);
                                setTaskAdapter.notifyDataSetChanged();

                                lv_task_chooser.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                                    @Override
                                    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                                        populateSpinner(position);
                                    }
                                });
                            }

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

        Log.i("pointnotesfetch", "reached");
        queue_fetch.add(strreq_fetch);
    }
}

private void populateSpinner(final int position){

    url = "http://nmstech.in/coach/categorys.php";

    connMgr = (ConnectivityManager) ctx.getSystemService(Context.CONNECTIVITY_SERVICE);
    networkInfo = connMgr.getActiveNetworkInfo();

    if (!(networkInfo != null && networkInfo.isConnected())) {
        final AlertDialog.Builder builder1 = new AlertDialog.Builder(ctx);
        builder1.setTitle(getString(R.string.network_no_t));
        builder1.setMessage(getString(R.string.network_no_m));
        builder1.setPositiveButton("OK", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                dialog.dismiss();
            }
        });

        builder1.create().show();
    }

    else {
        Log.i("spinpop", "reached");
        StringRequest strreq_fetch1 = new StringRequest(Request.Method.GET, url,
                new Response.Listener<String>() {
                    @Override
                    public void onResponse(String Response) {
                        try {
                            cat_id = (int) lv_task_chooser.getItemIdAtPosition(position);

                            jsonArray1 = new JSONArray(Response);

                            final AlertDialog.Builder builder = new AlertDialog.Builder(ctx);
                            builder.setTitle("Subtopics");

                            connMgr = (ConnectivityManager) ctx.getSystemService(Context.CONNECTIVITY_SERVICE);
                            networkInfo = connMgr.getActiveNetworkInfo();

                            category = jsonArray1.getJSONObject(cat_id).getString("cat_name");

                            int k = 0;

                            try {
                                   for (int i = 0; i < jsonArray1.getJSONObject(position).getJSONArray("sub_cat").length(); i++){

                                    array = new String[jsonArray1.getJSONObject(position).getJSONArray("sub_cat").length()];
                                    sub_cat_id = new int[jsonArray1.getJSONObject(position).getJSONArray("sub_cat").length()];

                                    array[i] = jsonArray1.getJSONObject(position).getJSONArray("sub_cat").getJSONObject(i).getString("sub_cat_name");
                                    sub_cat_id[k++] = jsonArray1.getJSONObject(position).getJSONArray("sub_cat").getJSONObject(i).getInt("sub_cat_id");
                                    Log.i("sub_cat_id", String.valueOf(sub_cat_id[k-1]));
                                    Log.i("sub_cat", array[i]);
                                }

                                scAdapter = new ArrayAdapter<String>(ctx, android.R.layout.simple_spinner_dropdown_item, array);
                            }
                            catch (Exception e){
                                e.printStackTrace();
                            }

                            builder.setItems(array, new DialogInterface.OnClickListener() {
                                @Override
                                public void onClick(DialogInterface dialog, int which) {
                                    dialog.dismiss();

                                    Bundle cat_args = new Bundle();
                                    cat_args.putInt("sub_cat_id", sub_cat_id[which]);
                                    cat_args.putString("sub_cat", array[which]);

                                    Fragment fragment = new Exercise();
                                    FragmentTransaction fragmentTransaction = getActivity().getSupportFragmentManager().beginTransaction();
                                    fragment.setArguments(cat_args);
                                    fragmentTransaction.replace(R.id.mainFrame, fragment);
                                    fragmentTransaction.commit();
                                }
                            });

                            builder.show();

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

        Log.i("pointnotesfetch", "reached");
        queue_fetch1.add(strreq_fetch1);
    }
}
}

编辑：添加完整的堆栈跟踪

06-29 10：38：25.499 9183-9183 / nmss.example.com.coach E / AndroidRuntime：致命异议：主要处理：nmss.example.com.coach，PID：9183 java.lang.NullPointerException：尝试调用虚方法＆＃39; java.lang.String java.lang.Object.toString（）＆＃39;在null对象上参考在 android.widget.ArrayAdapter.createViewFromResource（ArrayAdapter.java:409）在android.widget.ArrayAdapter.getView（ArrayAdapter.java:371）在android.widget.AbsListView.obtainView（AbsListView.java:2367）在android.widget.ListView.measureHeightOfChildren（ListView.java:1326）在android.widget.ListView.onMeasure（ListView.java:1233）在android.view.View.measure（View.java:19756）在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:6124）在android.widget.FrameLayout.onMeasure（FrameLayout.java:185）在android.view.View.measure（View.java:19756）在 android.support.v7.widget.AlertDialogLayout.tryOnMeasure（AlertDialogLayout.java:135）在 android.support.v7.widget.AlertDialogLayout.onMeasure（AlertDialogLayout.java:63）在android.view.View.measure（View.java:19756）在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:6124）在android.widget.FrameLayout.onMeasure（FrameLayout.java:185）在 android.support.v7.widget.ContentFrameLayout.onMeasure（ContentFrameLayout.java:139）在android.view.View.measure（View.java:19756）在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:6124）在android.widget.FrameLayout.onMeasure（FrameLayout.java:185）在android.view.View.measure（View.java:19756）在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:6124）在android.widget.FrameLayout.onMeasure（FrameLayout.java:185）在android.view.View.measure（View.java:19756）在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:6124）在 android.widget.LinearLayout.measureChildBeforeLayout（LinearLayout.java:1464）在android.widget.LinearLayout.measureVertical（LinearLayout.java:758）在android.widget.LinearLayout.onMeasure（LinearLayout.java:640）在android.view.View.measure（View.java:19756）在android.view.ViewGroup.measureChildWithMargins（ViewGroup.java:6124）在android.widget.FrameLayout.onMeasure（FrameLayout.java:185）在com.android.internal.policy.DecorView.onMeasure（DecorView.java:687）在android.view.View.measure（View.java:19756）在android.view.ViewRootImpl.performMeasure（ViewRootImpl.java:2283）在android.view.ViewRootImpl.measureHierarchy（ViewRootImpl.java:1343）在android.view.ViewRootImpl.performTraversals（ViewRootImpl.java:1619）在android.view.ViewRootImpl.doTraversal（ViewRootImpl.java:1258）在 android.view.ViewRootImpl $ TraversalRunnable.run（ViewRootImpl.java:6348）在 android.view.Choreographer $ CallbackRecord.run（Choreographer.java:871）在android.view.Choreographer.doCallbacks（Choreographer.java:683）在android.view.Choreographer.doFrame（Choreographer.java:619）在 android.view.Choreographer $ FrameDisplayEventReceiver.run（Choreographer.java:857）在android.os.Handler.handleCallback（Handler.java:751）在android.os.Handler.dispatchMessage（Handler.java:95）在android.os.Looper.loop（Looper.java:154）在android.app.ActivityThread.main（ActivityThread.java:6123） at java.lang.reflect.Method.invoke（Native Method）在 com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:867）在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:757）

编辑2：

为SetTaskAdapter类添加代码

public class SetTaskAdapter extends ArrayAdapter<SetTaskModel>{

private ArrayList<SetTaskModel> data;
Context mContext;

private static class ViewHolder{

    Button btn_category;
}

public SetTaskAdapter(ArrayList<SetTaskModel> data, Context mContext){

    super(mContext, R.layout.lv_task_chooser, data);
    this.data = data;
    this.mContext = mContext;
}

@NonNull
@Override
public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {

    SetTaskModel setTaskModel = getItem(position);
    ViewHolder viewHolder;
    final View result;

    if(convertView == null){
        viewHolder = new ViewHolder();
        LayoutInflater layoutInflater = LayoutInflater.from(getContext());
        convertView = layoutInflater.inflate(R.layout.lv_task_chooser, parent, false);

        viewHolder.btn_category = (Button)convertView.findViewById(R.id.btn_category);


        result = convertView;

        convertView.setTag(viewHolder);
    }

    else{
        viewHolder = (ViewHolder)convertView.getTag();
        result = convertView;
    }

    viewHolder.btn_category.setText(setTaskModel.getCategory());

    return convertView;
}
}

Answer 1

尝试此代码，初始化for循环中的字符串数组和int数组。

示例：

        array = new String[jsonArray1.getJSONObject(position).getJSONArray("sub_cat").length()];
        sub_cat_id = new int[jsonArray1.getJSONObject(position).getJSONArray("sub_cat").length()];

        try {
            for (int i = 0; i < jsonArray1.getJSONObject(position).getJSONArray("sub_cat").length(); i++){
                array[i] = jsonArray1.getJSONObject(position).getJSONArray("sub_cat").getJSONObject(i).getString("sub_cat_name");
                sub_cat_id[k++] = jsonArray1.getJSONObject(position).getJSONArray("sub_cat").getJSONObject(i).getInt("sub_cat_id");
                Log.i("sub_cat_id", String.valueOf(sub_cat_id[k-1]));
                Log.i("sub_cat", array[i]);
            }

            scAdapter = new ArrayAdapter<String>(ctx, android.R.layout.simple_spinner_dropdown_item, array);
        }
        catch (Exception e){
            e.printStackTrace();
        }

使用Volley

1 个答案: