Question

首先，当我触摸上下文菜单'删除'时，我的情况没有错误，但有任何响应。它似乎对计算机保持不可读状态。

DBHelper.java的getAmount calss

public int getAmount(Integer id){
    int amount = 0;
    SQLiteDatabase db=this.getReadableDatabase();
    Cursor res = db.rawQuery("SELECT id, amount FROM uselist WHERE id="+id,null);
    amount=res.getInt(res.getColumnIndex(USELIST_COLUMN_AMOUNT));
    return amount;
}

getAmount上面的代码已经使用了

@Override
public boolean onContextItemSelected(MenuItem item){
    int itemId = item.getItemId();
    switch (itemId){
        case R.id.context_item1 :
            Toast.makeText(this,"edit",Toast.LENGTH_SHORT).show();
            return true;
        case R.id.context_item2 :
            int amt=-mydb.getAmount(position);
            Toast.makeText(this,"delete",Toast.LENGTH_SHORT).show();
            mydb.deleteUseList(position);
            mydb.update("UPDATE uselist SET id = (id-1) WHERE id >"+ position+";");
            mydb.update("UPATE uselist SET balance = (balance+"+amt+") WHERE id>"+position+";");
            histories.clear(); //
            finish();
            startActivity(getIntent());
            return true;
    }
    return super.onContextItemSelected(item);
}

我猜'int amt = -mydb.getAmount（position）;'代码或getAmount类错误，因为删除Toast没有出现。

Answer 1

试试这个：

public int getAmount(Integer id){
    int amount = 0;
    SQLiteDatabase db=this.getReadableDatabase();

    Cursor res = db.rawQuery("SELECT id, amount FROM uselist WHERE id="+id,null);

            // looping through all rows and setting value to variable
            if (res.moveToFirst()) {
                do {
                    amount=res.getInt(res.getColumnIndex(USELIST_COLUMN_AMOUNT));
                } while (res.moveToNext());
            }

     return amount;
   }

从SQLite数据库获取数据时有任何响应

1 个答案: