如何在SQLite中更新特定行？

Question

我正在尝试更新用户的当前信用，但我不想替换该值，只需从微调器中添加选定的金额，然后将其添加到用户的当前信用？ 谢谢。

我的数据库代码？

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);
    }
}

需要执行actoin的类：

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

首先，您应该具有一个ID，该ID可让您找到您感兴趣的用户。进行选择以获取存储在数据库中的当前值。 将值解析为整数，然后添加“新”货币。 最后，更新数据库中的值。

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);
    }

当然，您必须检查游标是否正好返回一行，并进行其他一些检查。