java - 创建异步任务时出现下划线错误

Question

我在从 SQL Server 检索数据时创建了一个异步任务像这样

    private class MyAsyncTask extends AsyncTask<String, Void, String> {
        protected void onPreExecute() {
            // Runs on the UI thread before doInBackground
            // Good for toggling visibility of a progress indicator
            progressBar.setVisibility(ProgressBar.VISIBLE);
        }

        protected String doInBackground(String... strings) {
            String someBitmap ="";
            String menuListSTR = "";
            if (MenuActivity.Prst_ID.trim() == "-1")
                menuListSTR = "Select ID,Code,Name,Name2 From Presets Where Active = 1 And Rest_ID_Active = 1 AND OutLet_ID_Active = 1 ORDER BY Code";
            else
                menuListSTR = "select dbo.MenuItems.Item_ID, dbo.Items.Code, dbo.Items.Name, dbo.Items.Name2, dbo.Items.PrintOnChick, dbo.Items.Taxable, dbo.Items.NoServiceCharge, dbo.Items.PrintOnReport,Case { fn IFNULL ((SELECT Price_Value FROM dbo.ItemsPrices WHERE (PriceLVL_ID = 1) AND (Item_ID = dbo.Items.ID)), 0) } when 0 then dbo.Items.StaticPrice Else { fn IFNULL ((SELECT Price_Value FROM dbo.ItemsPrices WHERE (PriceLVL_ID = 1) AND (Item_ID = dbo.Items.ID)), dbo.Items.StaticPrice) } END AS Price From dbo.MenuItems LEFT OUTER JOIN dbo.Items ON dbo.MenuItems.Item_ID = dbo.Items.ID Where  (dbo.MenuItems.Preset_ID = " + MenuActivity.Prst_ID + ") AND (dbo.MenuItems.Rest_ID_Active = " + ConnectionClass.Rest_ID + ") AND (dbo.MenuItems.OutLet_ID_Active = " + ConnectionClass.OutletID + ") AND (dbo.Items.Active = 1) ORDER BY dbo.MenuItems.SortNumber";

            ResultSet rs = ConnectionClass.Ret_RS(menuListSTR);
            try {
                while (rs.next()) {
                    SortedMap<String, String> sm = new TreeMap<String, String>();
                    sm.put("Item_ID", rs.getString("Item_ID"));
                    sm.put("Name", rs.getString("Name"));
                    sm.put("Price", rs.getString("Price"));
                    sm.put("PrintOnChick", rs.getString("PrintOnChick"));
                    sm.put("Taxable", rs.getString("Taxable"));
                    sm.put("NoServiceCharge", rs.getString("NoServiceCharge"));
                    sm.put("PrintOnReport", rs.getString("PrintOnReport"));
                    if (TablesFragment.Check_Items.containsKey(rs.getString("Item_ID"))) {
                        SortedMap<String, String> sm1 = TablesFragment.Check_Items.get(rs.getString("Item_ID"));
                        sm.put("Qty", sm1.get("Qty"));
                    } else
                        sm.put("Qty", "0");
                    alphabets.add(sm);
                    listMenuArray.add(rs.getString("Name"));

                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
            return someBitmap;
        }

//        protected void onProgressUpdate(Progress... values) {
//            // Executes whenever publishProgress is called from doInBackground
//            // Used to update the progress indicator
//            progressBar.setProgress(values[0]);
//        }

        protected void onPostExecute(Bitmap result) {
            // This method is executed in the UIThread
            // with access to the result of the long running task
            menuListView.setAdapter(new CustomMenuLVAdapter(this, listMenuArray, alphabets));
            // Hide the progress bar
            progressBar.setVisibility(ProgressBar.INVISIBLE);
        }
    }

我收到了这样的带下划线的错误 这是我的 fragment ，我在上面放置了一个异步任务方法

package abtech.waiteriano.com.waitrer.fragments;

import android.graphics.Bitmap;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ListView;
import android.widget.ProgressBar;

import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.SortedMap;
import java.util.TreeMap;

import abtech.waiteriano.com.waitrer.MenuActivity;
import abtech.waiteriano.com.waitrer.R;
import abtech.waiteriano.com.waitrer.adapters.CustomMenuLVAdapter;
import abtech.waiteriano.com.waitrer.connection_class.ConnectionClass;

public class LVMenuFragment extends android.app.Fragment {
    View rootView;
    ListView menuListView;
    public static ArrayList<String> listMenuArray = new ArrayList<String>();
    ArrayList<SortedMap> alphabets = new ArrayList<SortedMap>();

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

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        rootView = inflater.inflate(R.layout.fragment_lvmenu, container, false);
        menuListView = (ListView) rootView.findViewById(R.id.listView);
        listMenuArray.clear();
        alphabets.clear();
        String menuListSTR = "";
        if (MenuActivity.Prst_ID.trim() == "-1")
            menuListSTR = "Select ID,Code,Name,Name2 From Presets Where Active = 1 And Rest_ID_Active = 1 AND OutLet_ID_Active = 1 ORDER BY Code";
        else
            menuListSTR = "select dbo.MenuItems.Item_ID, dbo.Items.Code, dbo.Items.Name, dbo.Items.Name2, dbo.Items.PrintOnChick, dbo.Items.Taxable, dbo.Items.NoServiceCharge, dbo.Items.PrintOnReport,Case { fn IFNULL ((SELECT Price_Value FROM dbo.ItemsPrices WHERE (PriceLVL_ID = 1) AND (Item_ID = dbo.Items.ID)), 0) } when 0 then dbo.Items.StaticPrice Else { fn IFNULL ((SELECT Price_Value FROM dbo.ItemsPrices WHERE (PriceLVL_ID = 1) AND (Item_ID = dbo.Items.ID)), dbo.Items.StaticPrice) } END AS Price From dbo.MenuItems LEFT OUTER JOIN dbo.Items ON dbo.MenuItems.Item_ID = dbo.Items.ID Where  (dbo.MenuItems.Preset_ID = " + MenuActivity.Prst_ID + ") AND (dbo.MenuItems.Rest_ID_Active = " + ConnectionClass.Rest_ID + ") AND (dbo.MenuItems.OutLet_ID_Active = " + ConnectionClass.OutletID + ") AND (dbo.Items.Active = 1) ORDER BY dbo.MenuItems.SortNumber";

        ResultSet rs = ConnectionClass.Ret_RS(menuListSTR);
        try {
            while (rs.next()) {
                SortedMap<String, String> sm = new TreeMap<String, String>();
                sm.put("Item_ID", rs.getString("Item_ID"));
                sm.put("Name", rs.getString("Name"));
                sm.put("Price", rs.getString("Price"));
                sm.put("PrintOnChick", rs.getString("PrintOnChick"));
                sm.put("Taxable", rs.getString("Taxable"));
                sm.put("NoServiceCharge", rs.getString("NoServiceCharge"));
                sm.put("PrintOnReport", rs.getString("PrintOnReport"));
                if (TablesFragment.Check_Items.containsKey(rs.getString("Item_ID"))) {
                    SortedMap<String, String> sm1 = TablesFragment.Check_Items.get(rs.getString("Item_ID"));
                    sm.put("Qty", sm1.get("Qty"));
                } else
                    sm.put("Qty", "0");
                alphabets.add(sm);
                listMenuArray.add(rs.getString("Name"));

            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        menuListView.setAdapter(new CustomMenuLVAdapter(this, listMenuArray, alphabets));
        new MyAsyncTask().execute();
        return rootView;
    }
    ProgressBar progressBar;
    // The types specified here are the input data type, the progress type, and the result type
    private class MyAsyncTask extends AsyncTask<String, Void, String> {
        protected void onPreExecute() {
            // Runs on the UI thread before doInBackground
            // Good for toggling visibility of a progress indicator
            progressBar.setVisibility(ProgressBar.VISIBLE);
        }

        protected String doInBackground(String... strings) {
            String someBitmap ="";
            String menuListSTR = "";
            if (MenuActivity.Prst_ID.trim() == "-1")
                menuListSTR = "Select ID,Code,Name,Name2 From Presets Where Active = 1 And Rest_ID_Active = 1 AND OutLet_ID_Active = 1 ORDER BY Code";
            else
                menuListSTR = "select dbo.MenuItems.Item_ID, dbo.Items.Code, dbo.Items.Name, dbo.Items.Name2, dbo.Items.PrintOnChick, dbo.Items.Taxable, dbo.Items.NoServiceCharge, dbo.Items.PrintOnReport,Case { fn IFNULL ((SELECT Price_Value FROM dbo.ItemsPrices WHERE (PriceLVL_ID = 1) AND (Item_ID = dbo.Items.ID)), 0) } when 0 then dbo.Items.StaticPrice Else { fn IFNULL ((SELECT Price_Value FROM dbo.ItemsPrices WHERE (PriceLVL_ID = 1) AND (Item_ID = dbo.Items.ID)), dbo.Items.StaticPrice) } END AS Price From dbo.MenuItems LEFT OUTER JOIN dbo.Items ON dbo.MenuItems.Item_ID = dbo.Items.ID Where  (dbo.MenuItems.Preset_ID = " + MenuActivity.Prst_ID + ") AND (dbo.MenuItems.Rest_ID_Active = " + ConnectionClass.Rest_ID + ") AND (dbo.MenuItems.OutLet_ID_Active = " + ConnectionClass.OutletID + ") AND (dbo.Items.Active = 1) ORDER BY dbo.MenuItems.SortNumber";

            ResultSet rs = ConnectionClass.Ret_RS(menuListSTR);
            try {
                while (rs.next()) {
                    SortedMap<String, String> sm = new TreeMap<String, String>();
                    sm.put("Item_ID", rs.getString("Item_ID"));
                    sm.put("Name", rs.getString("Name"));
                    sm.put("Price", rs.getString("Price"));
                    sm.put("PrintOnChick", rs.getString("PrintOnChick"));
                    sm.put("Taxable", rs.getString("Taxable"));
                    sm.put("NoServiceCharge", rs.getString("NoServiceCharge"));
                    sm.put("PrintOnReport", rs.getString("PrintOnReport"));
                    if (TablesFragment.Check_Items.containsKey(rs.getString("Item_ID"))) {
                        SortedMap<String, String> sm1 = TablesFragment.Check_Items.get(rs.getString("Item_ID"));
                        sm.put("Qty", sm1.get("Qty"));
                    } else
                        sm.put("Qty", "0");
                    alphabets.add(sm);
                    listMenuArray.add(rs.getString("Name"));

                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
            return someBitmap;
        }

//        protected void onProgressUpdate(Progress... values) {
//            // Executes whenever publishProgress is called from doInBackground
//            // Used to update the progress indicator
//            progressBar.setProgress(values[0]);
//        }

        protected void onPostExecute(Bitmap result) {
            // This method is executed in the UIThread
            // with access to the result of the long running task
            menuListView.setAdapter(new CustomMenuLVAdapter(this, listMenuArray, alphabets));
            // Hide the progress bar
            progressBar.setVisibility(ProgressBar.INVISIBLE);
        }
    }

}

这是我的适配器类

package abtech.waiteriano.com.waitrer.adapters;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.RelativeLayout;
import android.widget.TextView;

import java.util.ArrayList;
import java.util.SortedMap;

import abtech.waiteriano.com.waitrer.R;
import abtech.waiteriano.com.waitrer.fragments.LVMenuFragment;
import abtech.waiteriano.com.waitrer.fragments.TablesFragment;

/**
 * Created by dell on 3/7/2017.
 */

public class CustomMenuLVAdapter extends BaseAdapter {
    ArrayList<String> resultMenuItems;
    ArrayList<SortedMap> Items_Details;
    LVItemHolder lvItemHolder;
    Context context;
    private static LayoutInflater inflater = null;

    public CustomMenuLVAdapter(LVMenuFragment lvMenuFragment, ArrayList<String> listMenuArray, ArrayList<SortedMap> alphabets) {
        resultMenuItems = listMenuArray;
        Items_Details = alphabets;
        context = lvMenuFragment.getActivity();
        inflater = (LayoutInflater) context.
                getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    }

    @Override
    public int getCount() {
        return resultMenuItems.size();
    }

    @Override
    public Object getItem(int position) {
        return position;
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    public class LVItemHolder {
        TextView listMenuTV, txtQTY;
        RelativeLayout qtyView;
        Button minusBtn;
    }

    @Override
    public View getView(final int position, View convertView, ViewGroup parent) {
        final LVItemHolder lvItemHolder = new LVItemHolder();
        View rowView;
        rowView = inflater.inflate(R.layout.menu_list_item, null);
        lvItemHolder.listMenuTV = (TextView) rowView.findViewById(R.id.menulistTV2);
        lvItemHolder.txtQTY = (TextView) rowView.findViewById(R.id.txtQTY);
        lvItemHolder.minusBtn = (Button) rowView.findViewById(R.id.minusBtn);
        lvItemHolder.listMenuTV.setText(resultMenuItems.get(position));

        SortedMap<String, String> sm = Items_Details.get(position);
        lvItemHolder.txtQTY.setText(sm.get("Qty"));

        rowView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                int q = 0;
                q = Integer.valueOf(lvItemHolder.txtQTY.getText().toString());
                q++;
                lvItemHolder.txtQTY.setText("" + q);
                SortedMap<String, String> sm = Items_Details.get(position);
                sm.put("Qty", "" + q);
                TablesFragment.Check_Items.put(sm.get("Item_ID"), sm);
                //                Toast.makeText(context, "You Clicked "+resultMenuItems.get(position), Toast.LENGTH_LONG).show();
            }
        });
        lvItemHolder.minusBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                int q = 0;
                q = Integer.valueOf(lvItemHolder.txtQTY.getText().toString());
                if (q > 0)
                    q--;
                lvItemHolder.txtQTY.setText("" + q);
                SortedMap<String, String> sm = Items_Details.get(position);
                sm.put("Qty", "" + q);
                TablesFragment.Check_Items.put(sm.get("Item_ID"), sm);
            }
        });
        return rowView;
    }
}

android 监控错误

03-22 17:20:12.515 29962-30011/abtech.waiteriano.com.waitrer E/GED: Failed to get GED Log Buf, err(0)
03-22 17:20:12.531 29962-30011/abtech.waiteriano.com.waitrer E/[PropSet]: connect fail
03-22 17:20:12.531 29962-30011/abtech.waiteriano.com.waitrer E/libc: __system_property_set error : retry fail, errno 13(Permission denied)
03-22 17:20:12.531 29962-30011/abtech.waiteriano.com.waitrer E/[PropSet]: send_prop_msg return err -5
03-22 17:20:17.485 29962-29962/abtech.waiteriano.com.waitrer E/AndroidRuntime: FATAL EXCEPTION: main
                                                                               Process: abtech.waiteriano.com.waitrer, PID: 29962
                                                                               java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ProgressBar.setVisibility(int)' on a null object reference
                                                                                   at abtech.waiteriano.com.waitrer.fragments.LVMenuFragment$MyAsyncTask.onPreExecute(LVMenuFragment.java:85)
                                                                                   at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:591)
                                                                                   at android.os.AsyncTask.execute(AsyncTask.java:539)
                                                                                   at abtech.waiteriano.com.waitrer.fragments.LVMenuFragment.onCreateView(LVMenuFragment.java:76)
                                                                                   at android.app.Fragment.performCreateView(Fragment.java:2069)
                                                                                   at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:899)
                                                                                   at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1072)
                                                                                   at android.app.BackStackRecord.run(BackStackRecord.java:852)
                                                                                   at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1478)
                                                                                   at android.app.FragmentManagerImpl$1.run(FragmentManager.java:452)
                                                                                   at android.os.Handler.handleCallback(Handler.java:815)
                                                                                   at android.os.Handler.dispatchMessage(Handler.java:104)
                                                                                   at android.os.Looper.loop(Looper.java:214)
                                                                                   at android.app.ActivityThread.main(ActivityThread.java:6102)
                                                                                   at java.lang.reflect.Method.invoke(Native Method)
                                                                                   at java.lang.reflect.Method.invoke(Method.java:372)
                                                                                   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1028)
                                                                                   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:823)

Answer 1

使用LVMenuFragment.this，因为只有使用this才会引用AsyncTask类。您想要传递 LVMenuFragment 对象，而不是 AsyncTask。