java - How To Test If Cursor Is Empty in a SQLiteDatabase Query

Question

I have an SQL table which is created by the following code:

public void onCreate(SQLiteDatabase db) {
    db.execSQL("CREATE TABLE " + TABLE_NAME + " (" + _ID
        + " INTEGER PRIMARY KEY AUTOINCREMENT, " + SUBJECT
        + " TEXT NOT NULL," + TOPIC + " TEXT NOT NULL, "
        + LECTURENUMBER + " TEXT NOT NULL, " + PAGENUMBER
        + " TEXT NOT NULL, " + DATE + " TEXT NOT NULL, " + _DATA
        + " TEXT NOT NULL);");
}

I query the table as follows:

String sql = "SELECT " + _ID + "," + SUBJECT + " FROM " + TABLE_NAME
    + " GROUP BY " + SUBJECT + ";";

Cursor cursor = subjects.getReadableDatabase().rawQuery(sql, null);

The problem is I have to start an Activity A if the cursor is empty(i.e. the table is storing no values) and Activity B if the cursor is not empty(i.e. table is filled).

I am unable to find a method which can tell me if the table is empty or not. I Have tried to used Log as follows:

private void showSubjectsOnList() {
    String sql = "SELECT " + _ID + "," + SUBJECT + " FROM " + TABLE_NAME
        + " GROUP BY " + SUBJECT + ";";

    Cursor cursor = subjects.getReadableDatabase().rawQuery(sql, null);

    Log.d("Events",Integer.toString(cursor.getCount()));
    if(cursor.isNull(0)!=false){
        cursor.close();
        subjects.close();
        startActivity(new Intent(this,OpenScreen.class));
    }
}

But the LOG shows 1, if the table is empty...and again 1, if table has 1 entry....it shows 2, if table has two entries and so on.

Can you suggest some method of solving my problem of starting different activities based on if cursor is empty or not.

Answer 1

What about testing the cursor like this, and then doing what you've said:

if(cursor!=null && cursor.getCount()>0)

getCount ()

Returns the numbers of rows in the cursor

http://developer.android.com/reference/android/database/Cursor.html#getCount()