ActiveRecord getId（）方法返回NULL

Question

您好我正在使用ActiveAndroid将一些数据存储在本地数据库中，我得到一个非常奇怪的行为。我创建了我的表，当我尝试使用getId（）检索元素的ID时，我得到一个空指针异常...但是所有其他字段都在那里而不是null。

之前有人遇到过这个吗？

以下是一些代码：

package ro.gebs.captoom.datamodel;

import java.io.Serializable;

import ro.gebs.captoom.database.CaptoomSQLiteHelper;

import com.activeandroid.Model;
import com.activeandroid.annotation.Column;
import com.activeandroid.annotation.Table;

@Table(name = CaptoomSQLiteHelper.TABLE_MILEAGE)
public class Mileage extends Model implements Serializable, Comparable<Mileage>{

    private static final long serialVersionUID = 1L;
    @Column(name = CaptoomSQLiteHelper.COLUMN_REMOTE_ID)
    private String folderId;
    @Column(name = CaptoomSQLiteHelper.COLUMN_START_DATE)
    private String startDate;
    @Column(name = CaptoomSQLiteHelper.COLUMN_END_DATE)
    private String endDate;
    @Column(name = CaptoomSQLiteHelper.COLUMN_DISTANCE)
    private String distance;
    @Column(name = CaptoomSQLiteHelper.COLUMN_CURRENCY)
    private String currency;
    @Column(name = CaptoomSQLiteHelper.COLUMN_UNIT)
    private String unit;
    @Column(name = CaptoomSQLiteHelper.COLUMN_PRICE)
    private String price;
    @Column(name = CaptoomSQLiteHelper.COLUMN_DETAILS)
    private String details;
    @Column(name = CaptoomSQLiteHelper.COLUMN_SYNC)
    private int isSynchronized;

    public Mileage(){
        super();
    }

    public Mileage(String folder_id, String start_date, String end_date, String distance, String currency, String unit, String price, String details, int synced){
        super();
        this.folderId = folder_id;
        this.startDate = start_date;
        this.endDate = end_date;
        this.distance = distance;
        this.currency = currency;
        this.unit = unit;
        this.price = price;
        this.details = details;
        this.setIsSynchronized(synced);
    }

    @Override
    public int compareTo(Mileage another) {
        return this.getId().compareTo(another.getId());
    }

    public String getFolderId() {
        return folderId;
    }

    public void setFolderId(String folderId) {
        this.folderId = folderId;
    }

    public String getStartDate() {
        return startDate;
    }

    public void setStartDate(String startDate) {
        this.startDate = startDate;
    }

    public String getEndDate() {
        return endDate;
    }

    public void setEndDate(String endDate) {
        this.endDate = endDate;
    }

    public String getDistance() {
        return distance;
    }

    public void setDistance(String distance) {
        this.distance = distance;
    }

    public String getCurrency() {
        return currency;
    }

    public void setCurrency(String currency) {
        this.currency = currency;
    }

    public String getUnit() {
        return unit;
    }

    public void setUnit(String unit) {
        this.unit = unit;
    }

    public String getDetails() {
        return details;
    }

    public void setDetails(String details) {
        this.details = details;
    }

    public String getPrice() {
        return price;
    }

    public void setPrice(String price) {
        this.price = price;
    }

    public int getIsSynchronized() {
        return isSynchronized;
    }

    public void setIsSynchronized(int isSynchronized) {
        this.isSynchronized = isSynchronized;
    }

    @Override
    public String toString(){
        return this.details + "+++" + this.isSynchronized;
    }

}

这是我尝试检索的地方：

package ro.gebs.captoom.database;

import java.util.ArrayList;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Set;

import ro.gebs.captoom.datamodel.Mileage;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;

import com.activeandroid.query.Select;

public class MileageDataSource {

    // sync variables
    public final int SYNC_ID = 0x7f020001;
    public final int NEW_NOT_SYNC_ID = 0x7f020011;

    // Database fields
    private SQLiteDatabase database;
    private CaptoomSQLiteHelper dbHelper;
    private String[] columnsMileage = { CaptoomSQLiteHelper.COLUMN_ID,
            CaptoomSQLiteHelper.COLUMN_START_DATE,
            CaptoomSQLiteHelper.COLUMN_END_DATE,
            CaptoomSQLiteHelper.COLUMN_DISTANCE,
            CaptoomSQLiteHelper.COLUMN_CURRENCY,
            CaptoomSQLiteHelper.COLUMN_UNIT, CaptoomSQLiteHelper.COLUMN_PRICE,
            CaptoomSQLiteHelper.COLUMN_DETAILS,
            CaptoomSQLiteHelper.COLUMN_SYNC,
            CaptoomSQLiteHelper.COLUMN_REMOTE_ID };

    private boolean isOpen;

    public MileageDataSource(Context context) {
        setDbHelper(new CaptoomSQLiteHelper(context));
        isOpen = false;
    }

    public void open() {
        if (!isOpen) {
            isOpen = true;
        }
    }

    public void close() {
        if (isOpen) {
            isOpen = false;
        }
    }

    public Mileage createMileage(String folder_id, String start_date,
            String end_date, String distance, String currency, String unit,
            String price, String details) {
        Mileage newMileage = new Mileage(folder_id, start_date, end_date,
                distance, currency, unit, price, details, NEW_NOT_SYNC_ID);
        newMileage.save();
        return newMileage;
    }

    public Mileage updateMileage(long id, String folder_id, String start_date,
            String end_date, String distance, String currency, String unit,
            String price, String details) {
        Mileage r = this.getMileageByID(id);
        System.out.println("This mileage ID is the problem!!" + r.getId());
        r.setFolderId(folder_id);
        r.setStartDate(start_date);
        r.setEndDate(end_date);
        r.setDistance(distance);
        r.setCurrency(currency);
        r.setUnit(unit);
        r.setPrice(price);
        r.setDetails(details);
        r.setIsSynchronized(NEW_NOT_SYNC_ID);
        r.save();
        return r;
    }

    public void syncMileage(Mileage r) {
        r.setIsSynchronized(SYNC_ID);
        r.save();
    }

    public Mileage getMileageByID(long id) {
        Mileage r = new Mileage();
        ArrayList<Mileage> allMileages = this.selectAllMileages();
        for (int i = 0; i < allMileages.size(); i++) {
            System.out.println("in getmileageby id:"
                    + allMileages.get(i).getId());
            if (allMileages.get(i).getId() == id) {

                r = allMileages.get(i);
            }
        }
        return r;
    }

    public ArrayList<Mileage> selectAllMileages() {
        ArrayList<Mileage> allReceipts = new ArrayList<Mileage>();

        List<Mileage> selMileages = new Select().from(
                ro.gebs.captoom.datamodel.Mileage.class).execute();
        allReceipts.addAll(selMileages);

        return allReceipts;
    }

    public ArrayList<Mileage> findMileagessByDate(String myDate, long folder_id) {
        ArrayList<Mileage> allMileages = new ArrayList<Mileage>();
        List<Mileage> selMileages = new Select()
                .from(ro.gebs.captoom.datamodel.Mileage.class)
                .where(CaptoomSQLiteHelper.COLUMN_END_DATE + "='" + myDate
                        + "' AND " + CaptoomSQLiteHelper.COLUMN_REMOTE_ID
                        + " = " + folder_id).execute();
        allMileages.addAll(selMileages);
        return allMileages;
    }

    public ArrayList<Mileage> selectMileagesFromFolder(long folder_id) {
        ArrayList<Mileage> allMiles = new ArrayList<Mileage>();

        List<Mileage> selMiles = new Select()
                .from(ro.gebs.captoom.datamodel.Mileage.class)
                .where(CaptoomSQLiteHelper.COLUMN_REMOTE_ID + "=="
                        + String.valueOf(folder_id)).execute();
        allMiles.addAll(selMiles);

        return allMiles;
    }

    public int getUnsyncedMileagesCount(long folder_id) {
        List<Mileage> selReceipts = new Select()
                .from(ro.gebs.captoom.datamodel.Mileage.class)
                .where(CaptoomSQLiteHelper.COLUMN_REMOTE_ID + "=="
                        + String.valueOf(folder_id) + " AND "
                        + CaptoomSQLiteHelper.COLUMN_SYNC + "=="
                        + String.valueOf(NEW_NOT_SYNC_ID)).execute();
        return selReceipts.size();
    }

    public ArrayList<Mileage> selectUnsyncedMileages() {
        ArrayList<Mileage> allMileages = new ArrayList<Mileage>();

        List<Mileage> selReceipts = new Select()
                .from(ro.gebs.captoom.datamodel.Mileage.class)
                .where(CaptoomSQLiteHelper.COLUMN_SYNC + "=="
                        + String.valueOf(NEW_NOT_SYNC_ID)).execute();
        allMileages.addAll(selReceipts);

        return allMileages;
    }

    public String[] getColumnsFolder() {
        return columnsMileage;
    }

    public void setColumnsFolder(String[] columnsFolder) {
        this.columnsMileage = columnsFolder;
    }

    public CaptoomSQLiteHelper getDbHelper() {
        return dbHelper;
    }

    public void setDbHelper(CaptoomSQLiteHelper dbHelper) {
        this.dbHelper = dbHelper;
    }

    public SQLiteDatabase getDatabase() {
        return database;
    }

    public void setDatabase(SQLiteDatabase database) {
        this.database = database;
    }


}

此System.out.println("This mileage ID is the problem!!" + r.getId());的输出为空....

Answer 1

这可能不是答案，但我需要展示一段代码：

通过阅读AndroidActive（我从未使用过它），似乎你必须传递你想在newSelect（）上选择的列。如果你想得到所有，它可能是这样的：

    public ArrayList<Mileage> selectAllMileages() {
           ArrayList<Mileage> allReceipts = new ArrayList<Mileage>();

           List<Mileage> selMileages = new Select().all().from(  //put all() between
            ro.gebs.captoom.datamodel.Mileage.class).execute();
           allReceipts.addAll(selMileages);

          return allReceipts;
     }

这可能是你的getId（）返回null的原因。但是，就像我说的那样，这只是一个假设，我暂时无法测试它。