Android空指针异常SQLite

我试图从我的数据库中获取书籍数据，但我一直遇到NullPointerException。我有一个双数组条目，我想用一本书的项目和它的5个相应的细节填充。我知道我在InventoryAdapter数组中有额外的元素，我在这个方法中不使用这些元素，但我将它们保留在那里，因为我在其他地方使用它

错误发生在

条目[i][0]=InventoryAdapter.getInventoryByISBN（记录[i][0]）[1]并扩展为
Cursor Cursor=db.rawQuery（query，新字符串[]{ISBN}）

为什么光标处会出现错误？我原以为调用不存在的数组位置时可能会发生错误

主代码

int numEntries = 2;
Entries = new String[numEntries][5];
     int totalCount = 0;
     if (BuildConfig.DEBUG)
            Log.d(debug.LOG, "numEntries="+numEntries);

     Toast.makeText(ReportsByDateScreen.this, "numEntries="+numEntries, Toast.LENGTH_LONG).show();

    // Set up search array
    for(int i = 0; i < numEntries; i++)
    {
        Entries[i][0] = InventoryAdapter.getInventoryByISBN(records[i][0])[1];
        Entries[i][1] = InventoryAdapter.getInventoryByISBN(records[i][0])[2];
        Entries[i][2] = InventoryAdapter.getInventoryByISBN(records[i][0])[4];
        Entries[i][3] = InventoryAdapter.getInventoryByISBN(records[i][0])[3];
        for(int j = 0; j < records.length; j++)
        {
            if(records[j][0].equals(InventoryAdapter.getInventoryByISBN(records[i][0])[0]))
            {
                totalCount+=Integer.parseInt(InventoryAdapter.getInventoryByISBN(records[i][0])[8]);
            }
        }
        Entries[i][4] = ((Integer)totalCount).toString();
        reportArray.add(new ReportsItem(records[i][0],Entries[i]));
        totalCount = 0;
    }

int numEntries=2；
Entries=新字符串[numEntries][5]；
int totalCount=0；
if（BuildConfig.DEBUG）
Log.d（debug.Log，“numEntries=“+numEntries”）；
Toast.makeText（ReportsByDateScreen.this，“numEntries=“+numEntries，Toast.LENGTH_LONG）.show（）；
//设置搜索数组
for（int i=0；i

目录适配器

public static String[] getInventoryByISBN(String ISBN)
{
    String[] entry = new String[9];
    //Query
    String query = "select * from INVENTORY where ISBN = ?";
    Cursor cursor = db.rawQuery(query, new String[] {ISBN});
    if(cursor.getCount()<1) // title Not Exist
    {
        cursor.close();
        for(int i = 0; i < 9; i++)
            entry[i] = "Not Found";
        return entry;
    }
    cursor.moveToFirst();
    //put data into respective variable
    int publish = cursor.getInt(cursor.getColumnIndex("PUBLISH_DATE"));
    String publishdate = ((Integer)publish).toString();
    String title = cursor.getString(cursor.getColumnIndex("TITLE"));
    String author = cursor.getString(cursor.getColumnIndex("AUTHOR"));
    String callNumber = cursor.getString(cursor.getColumnIndex("CALL_NUMBER"));
    int available = cursor.getInt(cursor.getColumnIndex("AVAILABLE_COUNT"));
    String availablecount = ((Integer)available).toString();
    int inventory = cursor.getInt(cursor.getColumnIndex("INVENTORY_COUNT"));
    String inventorycount = ((Integer)inventory).toString();
    int due = cursor.getInt(cursor.getColumnIndex("DUE_PERIOD"));
    String dueperiod = ((Integer)due).toString();
    int checkoutcount = cursor.getInt(cursor.getColumnIndex("COUNT"));
    String count = ((Integer)checkoutcount).toString();
    //combine variables into one array
    entry[0] = ISBN;
    entry[1] = title;
    entry[2] = author;
    entry[3] = publishdate;
    entry[4] = callNumber;
    entry[5] = availablecount;
    entry[6] = inventorycount;
    entry[7] = dueperiod;
    entry[8] = count;
    cursor.close();
    return entry;
}

公共静态字符串[]getInventoryByISBN（字符串ISBN）
{
字符串[]项=新字符串[9]；
//质疑
String query=“从ISBN=？”的库存中选择*；
Cursor Cursor=db.rawQuery（查询，新字符串[]{ISBN}）；
如果（cursor.getCount（），这里有两种不同的可能性：


ISBN为空（扩展记录[i][0]也为空）
数据库为空

如果我是你，我会调查的。
使用调试器

我可以告诉您很多，因为您没有发布
SQLiteDatabase
的init代码