如何在SQLite中更新特定行？

Question

Im trying to update a users current credits, but I don't want to replace the value, just add on a selected amount from the spinner and add it on to the the users current credits? Thank you.

My database code?

package com.example.parkangel;

public class UDbHelper extends SQLiteOpenHelper
{
    public static final String KEY_ROWID = "_id";
    public static final String KEY_PFNAME = "payeeFname";
    public static final String KEY_PSNAME = "payeeSname";
    public static final String KEY_CARD = "card";
    public static final String KEY_CREDITS = "credits";

    private static final String DATABASE_NAME = "UserData.db";
    private static final String DATABASE_TABLE = "UserTable";
    private static final int DATABASE_VERSION = 1;

    //private UDbHelper dbHelper;
    //private final Context ourContext;
    private static UDbHelper instance;
    private SQLiteDatabase ourDatabase;

    public UDbHelper(Context context) 
    {   
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    public static UDbHelper getInstance(Context context)
    {
        if (instance == null)
        {
            instance = new UDbHelper(context);  
        }
        return instance;
    }

    @Override
    public void onCreate(SQLiteDatabase db) 
    {
        // TODO Auto-generated method stub
        db.execSQL("CREATE TABLE " + DATABASE_TABLE + " (" +
                KEY_ROWID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
                KEY_PFNAME + " TEXT NOT NULL, " + KEY_PSNAME + " 
                                    TEXT NOT NULL, " +
                KEY_CARD + " INTEGER NOT NULL, " + KEY_CREDITS + " 
                                    INTEGER NOT NULL);");   

        ContentValues values = new ContentValues();
        values.put(KEY_PFNAME, "Tutku"); 
        values.put(KEY_PSNAME, "Erbil");
        values.put(KEY_CARD, "12345677"); 
        values.put(KEY_CREDITS, 5);
        db.insert(DATABASE_TABLE, null, values);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) 
    {

        // TODO Auto-generated method stub
        db.execSQL("DROP TABLE IF EXISTS " + DATABASE_TABLE);
        onCreate(db);
    }

    public synchronized UDbHelper open() throws SQLException
    {
        System.out.println ("running open");
        if(ourDatabase == null || !ourDatabase.isOpen())
        ourDatabase = getWritableDatabase();
        return this;
    }   

    public String getData() 
    {
        // TODO Auto-generated method stub
        String[] columns = new String[] {KEY_ROWID, KEY_PFNAME, KEY_PSNAME,
            KEY_CARD, KEY_CREDITS};
        Cursor  c = ourDatabase.query(DATABASE_TABLE, columns, null, null, 
                                                 null, null, null);
        String result = " ";

        int iRow = c.getColumnIndexOrThrow(KEY_ROWID);
        int iPFname = c.getColumnIndexOrThrow(KEY_PFNAME);
        int iPSname = c.getColumnIndexOrThrow(KEY_PSNAME);
        int iCard = c.getColumnIndexOrThrow(KEY_CARD);
        int iCredits = c.getColumnIndexOrThrow(KEY_CREDITS);

        for(c.moveToFirst(); !c.isAfterLast(); c.moveToNext()){
            result = result + c.getString(iRow) + " " + 
                            c.getString(iPFname) + " " +
            c.getString(iPSname) + " " + c.getString(iCard) + " " +
            c.getString(iCredits) + "\n";
        }
        return result;
    }

    public void upDateUser(String money) {
        // TODO Auto-generated method stub
        ContentValues cvUpdate = new ContentValues();
        cvUpdate.put(KEY_CREDITS, money);
        ourDatabase.update(DATABASE_TABLE, cvUpdate, null, null);
    }
}

Class that needs to perform the actoin:

package com.example.parkangel;  

public class Balance extends Activity implements OnClickListener{

Button add;
TextView display;
Spinner spinner3;
Integer[] money = new Integer[] {1, 2, 5, 10};  

protected void onCreate(Bundle savedInstanceState) {                
    super.onCreate(savedInstanceState);
    setContentView(R.layout.balance_layout);
    TextView tv = (TextView) findViewById(R.id.firstn);
    UDbHelper db = new UDbHelper(this);
    db.open();
    String data = db.getData();
    //db.addUser();
    db.close();
    tv.setText(data);

    ArrayAdapter<Integer> adapter3 = new ArrayAdapter<Integer>(Balance.this,   
                                     android.R.layout.simple_spinner_item, money);

    spinner3 = (Spinner) findViewById (R.id.moneytoadd);
    spinner3.setAdapter(adapter3);

    add = (Button) findViewById(R.id.topup);
    add.setOnClickListener(this);
    //add = (Button) findViewById(R.id.topup);      
}

public void onClick(View arg0)
{
    switch (arg0.getId()){
    case R.id.topup:

        boolean work = true;
        try{
        String money = spinner3.getContext().toString();

        UDbHelper ud = new UDbHelper(this);
        ud.open();
        ud.upDateUser(money);
        ud.close();

    }catch (Exception e){
        work = false;
        String error = e.toString();
        Dialog d = new Dialog(this);
        d.setTitle("Unable To TopUp!");
        TextView dg = new TextView(this);
        dg.setText(error);
        d.setContentView(dg);
        d.show();
}finally{
    if(work){
        Dialog d = new Dialog(this);
        d.setTitle("You Have ToppedUp!");
        TextView dg = new TextView(this);
        dg.setText("TopUp Successful");
        d.setContentView(dg);
        d.show();
            }
        }   
        break;
}
}

public void updateActivity(View view){
    Intent book = new Intent(Balance.this, BookTicket.class);
    startActivity(book);
}

public void addBalance(View view){
    Intent addB = new Intent(Balance.this, Balance.class);
    startActivity(addB);
}

public void doUpdate(View view){
    Intent upd = new Intent(Balance.this, UpdateTicket.class);
    startActivity(upd);
}

}

Answer 1

First of all you should have an ID that will let you find the user you are interested in. That do a select to get the current value that is stored in database. Parse the value to integer and add "new" money. And finally, update the value in database.

public void upDateUser(String ID, String money) {
        String query = "Select money from TABLE_NAME where ID = " + ID;
        SQLiteDatabase db = this.getWriteableDatabase();
        Cursor cursor = db.rawQuery(selectQuery, null);
        int oldMoney = 0;
        if (cursor.moveToFirst()) {         
            oldMoney = Integer.parseInt(cursor.getString(0)); //Cause we get only from money column
        }
        ContentValues cvUpdate = new ContentValues();
        cvUpdate.put(KEY_CREDITS, oldMoney  + money);
        String filter = "UID" + "=" + ID;
        db.update(DATABASE_TABLE, cvUpdate, filter, null);
    }

Of course you have to check if cursor returns exactly one row and do some other checks.