Android：从sqlite数据库检索数据

Question

I currently I have my database set up like the following:

db.execSQL("CREATE TABLE " + DATABASE_TABLE + " (" + KEY_ROWID
                    + " INTEGER PRIMARY KEY AUTOINCREMENT, " + KEY_LOCKERNUMBER
                    + " TEXT NOT NULL, " + KEY_STATUS + " INTEGER, " + KEY_PIN
                    + " INTEGER);");

And I am trying to write a method to get the pin code from the column for a specific locker number. Any ideas? I am very new I would like think I would need to use the query function and a cursor. I just one to get the integer value and store it into an int variable so I can compare the pin codes from what the user types in to the one in the database.

Answer 1

Queries to database returns in a Cursor object . You should use the db.query() method to get a row(s). Pass the table name, an array of columns you want to get (or null if you want all of them), pass a selection string that should be like "id = ?" or "key > ?" , etc, then pass a String array containing the value for those ? inside the previous string, and finally pass null for having , groupBy and orderBy unless you want to use them.

Cursor cursor = db.query(TABLE_NAME, new String[] { KEY_ROWID }, "id = ?", new String[] { Integer.toString(id) }, null, null, null);

After you get the Cursor , do cursor.moveToFirst() or cursor.moveToPosition(0) (can't remember the exact method, but the point is to move the cursor to the first retrieved row)

then you're going to iterate through the cursor with

while(cursor.moveToNext()) {
     int keyRowIdColumnIndex = cursor.getColumnIndex(KEY_ROWID);
     int yourValue = cursor.getInt(keyRowIdColumnIndex);

     int keyLockNumberColumnIndex = cursor.getColumnIndex(KEY_LOCKNUMBER);
     int pin = cursor.getInt(keyLockNumberColumnIndex);
}

Answer 2

This is a pretty straight forward task and there is a bunch of tutorials, examples , similar questions on SO :

How to perform an SQLite query within an Android application?

In general - you need to query the database passing your search arguments. See the documentation .

It will return you a Cursor with the matching results, which you can then iterate over and manipulate as you wish .

Fyi - storing password in a database table is a bad idea. On Android databases can be accessed and easily read. You either need to encrypt your data or think of another way to store it if it's important.

Answer 3

         //Try This code 

         public String getLabeId(String LockNo)
     {

    ArrayList<String> Key_Pin_array = new ArrayList<String>();
    Cursor cur = db.rawQuery("SELECT * FROM  DATABASE_TABLE where KEY_LOCKERNUMBER = '" + LockNo + "'", null);
    try {
             while (cur.moveToNext()) 
              {
                    System.out.println("Key_Pin" + cur.getString(3));
                    Key_Pin_array.add(cur.getString(3));
              }
        } 
        catch (Exception e)
        {
                System.out.println("error in getLabelID in DB() :" + e);
        }
        finally 
        {
                cur.close();
        }
    return id;
 }