问题
I'm trying to add some records to a SQLite table, but LogCat is telling me the table does not exist. And DDMS shows that, yes, that table is not being/has not been created.
Yet I do create the table in the SQLiteOpenHelper class:
public class SQLiteHandlerDeliveryItem extends SQLiteOpenHelper {
. . .
@Override
public void onCreate(SQLiteDatabase sqLiteDatabase) {
String CREATE_DELIVERYITEMS_TABLE = "CREATE TABLE " +
TABLE_DELIVERYITEMS + "("
+ COLUMN_ID + " INTEGER PRIMARY KEY," + COLUMN_INVOICENUM + " TEXT,"
+ COLUMN_UPCPLU + " TEXT," + COLUMN_VENDORITEMID + " TEXT,"
+ COLUMN_PACKSIZE + " INTEGER," + COLUMN_DESCRIPTION + " TEXT,"
//+ COLUMN_COST + " REAL," + COLUMN_MARGIN + " REAL," + COLUMN_LISTPRICE + " REAL,"
+ COLUMN_COST + " REAL DEFAULT 0," + COLUMN_MARGIN + " REAL DEFAULT 0," +
COLUMN_LISTPRICE + " REAL DEFAULT 0,"
+ COLUMN_DEPTNUM + " INTEGER," + COLUMN_SUBDEPT + " TEXT," + COLUMN_QTY + " TEXT"
+ ")";
sqLiteDatabase.execSQL(CREATE_DELIVERYITEMS_TABLE);
}
I call the class's method which adds records:
SQLiteHandlerDeliveryItem sqliteHandler = new SQLiteHandlerDeliveryItem(SQLiteActivity.this, null);
sqliteHandler.addDeliveryItem(delItem);
This should call SQLiteHandlerDeliveryItem's constructor (when sqliteHandler is instantiated), but it doesn't! I've got a breakpoint in the onCreate() method, and sure enough - it's never reached.
Why? And how can I force the constructor to be called, so that the table is created?
The odd[est] thing is that I also put a breakpoint in the other (working) SQLiteOpenHelper class, and it is also not reached...what?!? It worked at least once, as the table does exist/was created from that code.
So there's obviously a hole in my swing somehwere; what am I misunderstanding or doing wrong?
UPDATE
I marked the answer as THE answer too soon.
As to:
"1. You must call getWritableDatabase() or getReadableDatabase() at some point."
I do call getWritableDatabase() in each method that creates or reads records, like so:
public long addDeliveryItem(DeliveryItem delItem) {
long IdAdded = 0;
ContentValues values = new ContentValues();
values.put(COLUMN_INVOICENUM, delItem.get_invoiceNumber());
. . .
values.put(COLUMN_QTY, delItem.get_quantity());
SQLiteDatabase db = this.getWritableDatabase(); <= Rot Cheer
if (db != null) {
IdAdded = db.insert(TABLE_DELIVERYITEMS, null, values);
}
. . .
...and as regards:
"2. In your constructor for SQLiteHandlerDeliveryItem, you must call super(...)."
I do call super in the class that extends SQLiteOpenHelper:
public SQLiteHandlerDeliveryItem(Context context, SQLiteDatabase.CursorFactory factory)
{
super(context, DATABASE_NAME, factory, DATABASE_VERSION);
}
So...I still don't know what the problem/solution is...
UPDATE 2
So what I see when attempting to insert a record into this table in LogCat is:
E/SQLiteLog﹕ (1) no such table: deliveryitems
Yet my code that attempts to add the record instantiates the corresponding/appropriate class that extends SQLiteOpenHelper like so:
else if ("Delivery Items".equals(tableName)) {
try {
JSONArray jsonArr = new JSONArray(result);
for (int i = 0; i < jsonArr.length(); i++) {
JSONObject jsonObj = jsonArr.getJSONObject(i);
String invNum = jsonObj.getString("invoiceNumber");
. . .
// Prepare for writing to db
DeliveryItem delItem = new DeliveryItem();
delItem.set_invoiceNumber(invNum);
. . .
SQLiteHandlerDeliveryItem sqliteHandler = new
SQLiteHandlerDeliveryItem(SQLiteActivity.this, null);
sqliteHandler.addDeliveryItem(delItem);
}
}
...and that class has the code to create the table:
public class SQLiteHandlerDeliveryItem extends SQLiteOpenHelper {
. . .
public SQLiteHandlerDeliveryItem(Context context, SQLiteDatabase.CursorFactory factory)
{
super(context, DATABASE_NAME, factory, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase sqLiteDatabase) {
String CREATE_DELIVERYITEMS_TABLE = "CREATE TABLE " +
TABLE_DELIVERYITEMS + "("
+ COLUMN_ID + " INTEGER PRIMARY KEY," + COLUMN_INVOICENUM + " TEXT,"
+ COLUMN_UPCPLU + " TEXT," + COLUMN_VENDORITEMID + " TEXT,"
+ COLUMN_PACKSIZE + " INTEGER," + COLUMN_DESCRIPTION + " TEXT,"
+ COLUMN_COST + " INTEGER," + COLUMN_MARGIN + " INTEGER," + COLUMN_LISTPRICE + " INTEGER,"
+ COLUMN_DEPTNUM + " INTEGER," + COLUMN_SUBDEPT + " TEXT," + COLUMN_QTY + " TEXT"
+ ")";
sqLiteDatabase.execSQL(CREATE_DELIVERYITEMS_TABLE);
}
So...what am I doing wrong, or failing to do right?
UPDATE 3
It's true the table is not being created. The err msg in LogCat indicates that to be the case (it's "no such table: delivertitems").
My constructor looks like this:
@Override
public void onCreate(SQLiteDatabase db) {
String CREATE_DELIVERYITEMS_TABLE = "CREATE TABLE " +
TABLE_DELIVERYITEMS + "("
+ COLUMN_ID + " INTEGER PRIMARY KEY," + COLUMN_INVOICENUM + " TEXT,"
+ COLUMN_UPCPLU + " TEXT," + COLUMN_VENDORITEMID + " TEXT,"
+ COLUMN_PACKSIZE + " INTEGER," + COLUMN_DESCRIPTION + " TEXT,"
+ COLUMN_COST + " INTEGER," + COLUMN_MARGIN + " INTEGER," + COLUMN_LISTPRICE + " INTEGER,"
+ COLUMN_DEPTNUM + " INTEGER," + COLUMN_SUBDEPT + " TEXT," + COLUMN_QTY + " TEXT"
+ ")";
db.execSQL(CREATE_DELIVERYITEMS_TABLE);
}
This code does, indeed, not get entered. So what hoop must I leap through to get the constructor to be called?
I would think that would happen when I instantiate the class:
SQLiteHandlerDeliveryItem sqliteHandler = new
SQLiteHandlerDeliveryItem(SQLiteActivity.this, null);
Even when it is called, how does the constructor know what the arg (SQLiteDatabase db) is - where does it get this value from?
I do have a database, with one table. It just refuses to add this second table.
As someone somewhere recommended, I'm adding a separate class that extends SQLiteOpenHelper for each table I want to add to the database.
When I get to that line:
SQLiteHandlerDeliveryItem sqliteHandler = new
SQLiteHandlerDeliveryItem(SQLiteActivity.this, null);
...and mash F7 to step into it, I reach the class constructor:
public SQLiteHandlerDeliveryItem(Context context, SQLiteDatabase.CursorFactory factory)
{
super(context, DATABASE_NAME, factory, DATABASE_VERSION);
}
...but not the onCreate event.
So it's "no wonder" I have no deliveryitems table, as the code to create said table never gets reached; but WHY does it not get reached - what must I do to get it to BE reached?
回答1:
You must call
getWritableDatabase()orgetReadableDatabase()at some point.In your constructor for
SQLiteHandlerDeliveryItem, you must call super(...).
回答2:
Firstly, the method SQLiteOpenHelper.onCreate() is not the constructor. I'm not sure, but it looks like you are mixing the 2 concepts up in the question.
Now onto trying to solve the problem...
It seems like your table is not being created. From the online help for SQLiteOpenHelper.onCreate():
public abstract void onCreate (SQLiteDatabase db)
Called when the database is created for the first time. This is where the creation of tables and the initial population of the tables should happen.
So this method will be called only once for a typical use case - when the app is first installed (first uses the database). At that point, onCreate() is called which creates the actual tables. But this is not called every time you run the app.
My advice to check if this is the problem - uninstall the app, and try again. Put a breakpoint in this method to make sure it does actually get run.
What can sometimes happen is that we have a database on the app, then update things to add a table, and forget to uninstall. Another correct way to do it would be to use the onUpgrade() method to add the new table.
Let me know how this pans out, or if I have misunderstood the issue.
回答3:
As I was hoping, it actually turns out to be an easy fix: simply increment the value of your database version. I read this on p. 262 of O'Reilly's "Programming Android":
DATABASE_VERSION ...If the version of the database on the machine is less than DATABASE_VERSION, the system runs your onUpgrade method to upgrade the database to the current level.
Thus, all you need to do is increment that number:
private static final int DATABASE_VERSION = 2;
// I changed it from "1" to "2", but you could change it to anything you want, I reckon (42, or 1776, or whatever).
Incrementing the version value causes onUpgrade to run, which drops the old version of the database and then calls onCreate:
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + TABLE_DELIVERYITEMS);
onCreate(db);
}
The onCreate() event then does exactly that - adding the DDL to create the table.
Here is the pertinent code in the class that extends SQLiteOpenHelper in context:
public class SQLiteHandlerDeliveryItem extends SQLiteOpenHelper {
private static final int DATABASE_VERSION = 2;
private static final String DATABASE_NAME = "HHS.db";
private static final String TABLE_DELIVERYITEMS = "deliveryitems";
private static final String COLUMN_ID = "_id";
. . .
private static final String COLUMN_QTY = "quantity";
public SQLiteHandlerDeliveryItem(Context context, SQLiteDatabase.CursorFactory factory)
{
super(context, DATABASE_NAME, factory, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
String CREATE_DELIVERYITEMS_TABLE = "CREATE TABLE " +
TABLE_DELIVERYITEMS + "("
+ COLUMN_ID + " INTEGER PRIMARY KEY," + COLUMN_INVOICENUM + " TEXT,"
. . .
+ COLUMN_DEPTNUM + " INTEGER," + COLUMN_SUBDEPT + " TEXT," + COLUMN_QTY + "
TEXT"
+ ")";
db.execSQL(CREATE_DELIVERYITEMS_TABLE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + TABLE_DELIVERYITEMS);
onCreate(db);
}
. . .
So it seems to me having multiple classes that extend SQLiteOpenHelper is a good thing, since you can thus keep your code separated, rather than have one gigantic/humongous pair of onUpgrade/onCreate spaghetti.
来源：https://stackoverflow.com/questions/23024438/why-is-my-constructor-not-getting-called