java - 使用 AsyncTask 用多个项目填充 ExpandableListView

Question

我想用自定义适配器填充 ExpandableListView。我在网上找到的是小时候只有一个 child (一个 TextView)。就我而言，我想让它在后台任务后填充多个子项和数据。

请帮我找出我做错了什么或者我应该如何处理错误，因为我不断得到

java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object java.util.HashMap.put(java.lang.Object, java.lang.Object)' on a null object reference
    at com.infy.texpetrol.Activity.CreditReportActivity$GetData.onPostExecute

CreditReportActivity

public class CreditReportActivity extends AppCompatActivity {

private static final String TAG = "CreditBillActivity";

private ConnectionClass connectionClass;
private ProgressDialog progressDialog;

private List<String> cListPetrol, cListDIESEL, cListSPEED, cListOIL;
ExpandableListAdapter listAdapter;
ExpandableListView expListView;
List<String> listDataHeader;
HashMap<String, List<String>> listDataChild;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_credit_report);
    String empCode = getIntent().getStringExtra("empCode");
    String shift = getIntent().getStringExtra("shift");
    String date = getIntent().getStringExtra("date");
    connectionClass = new ConnectionClass();

    expListView = findViewById(R.id.lvExpandable);

    GetData getData = new GetData();
    getData.execute(empCode);

}

@SuppressLint("StaticFieldLeak")
private class GetData extends AsyncTask {

    boolean bPetrolRS = false;
    boolean bDesiRS = false;
    boolean bSpedRS = false;
    boolean bOilRS = false;

    @Override
    protected Object doInBackground(Object[] objects) {
        String empCode = objects[0].toString();
        try {
            Connection con = connectionClass.CONN();

            String queryPetrol, queryDIESEL, queryOIL, querySPEED;

            queryDIESEL = "Some SQL QUERY";
            queryPetrol = "Some SQL QUERY";
            queryOIL = "Some SQL QUERY";
            querySPEED = "Some SQL QUERY";

            if (con != null) {
                Statement statement1 = con.createStatement();
                Statement statement2 = con.createStatement();
                Statement statement3 = con.createStatement();
                Statement statement4 = con.createStatement();

                ResultSet rsPetrol = statement1.executeQuery(queryPetrol);
                ResultSet rsDIESEL = statement2.executeQuery(queryDIESEL);
                ResultSet rsOIL = statement3.executeQuery(queryOIL);
                ResultSet rsSPEED = statement4.executeQuery(querySPEED);

                listDataHeader = new ArrayList<>();
                cListPetrol = new ArrayList<>();
                cListDIESEL = new ArrayList<>();
                cListSPEED = new ArrayList<>();
                cListOIL = new ArrayList<>();

                Log.d(TAG, "doInBackground: rsPetrol " + rsPetrol.next());

                if (rsPetrol.next()) {
                    while (rsPetrol.next()) {
                        bPetrolRS = true;
                        cListPetrol.add(rsPetrol.getString("PartyName")
                                + "#.#" + rsPetrol.getString("QTY")
                                + "#.#" + rsPetrol.getString("Amount"));
                    }
                } else {
                    bPetrolRS = false;
                    cListPetrol.add("NONE");
                }

                Log.d(TAG, "doInBackground: rsDIESEL " + rsDIESEL.next());

                if (rsDIESEL.next()) {
                    while (rsDIESEL.next()) {
                        bDesiRS = true;
                        cListDIESEL.add(rsDIESEL.getString("PartyName")
                                + "#.#" + rsDIESEL.getString("QTY")
                                + "#.#" + rsDIESEL.getString("Amount"));
                    }
                } else {
                    bDesiRS = false;
                    cListDIESEL.add("NONE");

                }
                Log.d(TAG, "doInBackground: rsSPEED " + rsSPEED.next());

                if (rsSPEED.next()) {
                    while (rsSPEED.next()) {
                        bSpedRS = true;
                        cListSPEED.add(rsSPEED.getString("PartyName")
                                + "#.#" + rsSPEED.getString("QTY")
                                + "#.#" + rsSPEED.getString("Amount"));
                    }
                } else {
                    bSpedRS = false;
                    cListSPEED.add("NONE");
                }

                Log.d(TAG, "doInBackground: rsOIL " + rsOIL.next());

                if (rsOIL.next()) {
                    while (rsOIL.next()) {
                        bOilRS = true;
                        cListOIL.add(rsOIL.getString("PartyName")
                                + "#.#" + rsOIL.getString("QTY")
                                + "#.#" + rsOIL.getString("Amount"));
                    }
                } else {
                    bSpedRS = false;
                    cListOIL.add("NONE");
                }

            } else {
                Log.d(TAG, "doInBackground: Error in Connection");
            }

        } catch (Exception e) {
            bPetrolRS = false;
            Log.d(TAG, "doInBackground: CATCH " + e.getMessage());
        }
        return empCode;
    }

    @Override
    protected void onPostExecute(Object o) {
        progressDialog.hide();

        if (!o.toString().isEmpty()) {

            listDataHeader.add("DIESEL");
            listDataHeader.add("PETROL");
            listDataHeader.add("SPEED");
            listDataHeader.add("OIL");

            if (bDesiRS) {
                Log.d(TAG, "onPostExecute: cListDIESEL " + cListDIESEL.size() + " listDataHeader.get(0) " + listDataHeader.get(0));
                listDataChild.put(listDataHeader.get(0), cListDIESEL);
            } else {
                Toast.makeText(CreditReportActivity.this, "NO DATA IN DIESEL", Toast.LENGTH_SHORT).show();
            }

            if (bPetrolRS) {
                Log.d(TAG, "onPostExecute: cListPetrol " + cListPetrol.size() + " listDataHeader.get(1) " + listDataHeader.get(1));
                listDataChild.put(listDataHeader.get(1), cListPetrol); //error gets me here
            } else {
                Toast.makeText(CreditReportActivity.this, "NO DATA IN PETROL", Toast.LENGTH_SHORT).show();
            }

            if (bOilRS) {
                listDataChild.put(listDataHeader.get(2), cListSPEED);
                Log.d(TAG, "onPostExecute: cListSPEED " + cListSPEED.size());
            } else {
                Toast.makeText(CreditReportActivity.this, "NO DATA IN SPEED", Toast.LENGTH_SHORT).show();
            }

            if (bSpedRS) {
                listDataChild.put(listDataHeader.get(3), cListOIL);
                Log.d(TAG, "onPostExecute: cListOIL " + cListOIL.size());
            } else {
                Toast.makeText(CreditReportActivity.this, "NO DATA IN OIL", Toast.LENGTH_SHORT).show();
            }

            listAdapter = new ExpandableListAdapter(CreditReportActivity.this, listDataHeader, listDataChild);

            expListView.setAdapter(listAdapter);
        } else {
            Toast.makeText(CreditReportActivity.this, "No Data", Toast.LENGTH_SHORT).show();
        }
    }

    @Override
    protected void onPreExecute() {
        progressDialog = new ProgressDialog(CreditReportActivity.this);
        progressDialog.setMessage("Getting your Report");
        progressDialog.show();
    }
}
}

ExpandableListAdapter

public class ExpandableListAdapter extends BaseExpandableListAdapter {

private Context _context;
private List<String> _listDataHeader; // header titles
// child data in format of header title, child title
private HashMap<String, List<String>> _listDataChild;

private String[] split;

public ExpandableListAdapter(Context _context, List<String> _listDataHeader, HashMap<String, List<String>> _listDataChild) {
    this._context = _context;
    this._listDataHeader = _listDataHeader;
    this._listDataChild = _listDataChild;
}

@Override
public Object getChild(int groupPosition, int childPosition) {
    return Objects.requireNonNull(this._listDataChild.get(this._listDataHeader.get(groupPosition))).get(childPosition);
}

@Override
public long getChildId(int groupPosition, int childPosition) {
    return childPosition;
}

@SuppressLint("InflateParams")
@Override
public View getChildView(int groupPosition, final int childPosition, boolean isLastChild, View convertView, ViewGroup parent) {

    final String childText = (String) getChild(groupPosition, childPosition);

    stringSplit(childText);

    if (convertView == null) {
        LayoutInflater Inflater = (LayoutInflater) this._context
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        convertView = Inflater.inflate(R.layout.child, null);
    }

    TextView txtPartyName = convertView.findViewById(R.id.txt_C_partyName);
    txtPartyName.setText(split[0]);

    TextView product = convertView.findViewById(R.id.txt_C_COUNT);
    product.setText(String.valueOf(childPosition));

    TextView qty = convertView.findViewById(R.id.txt_C_qty);
    qty.setText(split[1]);

    TextView amt = convertView.findViewById(R.id.txt_C_amt);
    amt.setText(split[2]);

    return convertView;
}

private void stringSplit(String childText) {
    split = childText.split("#.#");
}

@Override
public int getChildrenCount(int groupPosition) {
    return Objects.requireNonNull(this._listDataChild.get(this._listDataHeader.get(groupPosition)))
            .size();
}

@Override
public Object getGroup(int groupPosition) {
    return this._listDataHeader.get(groupPosition);
}

@Override
public int getGroupCount() {
    return this._listDataHeader.size();
}

@Override
public long getGroupId(int groupPosition) {
    return groupPosition;
}

@SuppressLint("InflateParams")
@Override
public View getGroupView(int groupPosition, boolean isExpanded,
                         View convertView, ViewGroup parent) {
    String headerTitle = (String) getGroup(groupPosition);
    if (convertView == null) {
        LayoutInflater infalInflater = (LayoutInflater) this._context
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        convertView = infalInflater.inflate(R.layout.header, null);
    }

    TextView lblListHeader = convertView.findViewById(R.id.lblListHeader);
    lblListHeader.setTypeface(null, Typeface.BOLD);
    lblListHeader.setText(headerTitle);

    return convertView;
}

@Override
public boolean hasStableIds() {
    return false;
}

@Override
public boolean isChildSelectable(int groupPosition, int childPosition) {
    return false;
}

Answer 1

您忘记初始化 listDataChild

HashMap<String, List<String>> listDataChild = new HashMap<>();