Android Cursor Index out of Bound Exception

问题:

is there any thing wrong with this code, i want to query for data by using barcode and it show me that Cursor Index out of Bound exception .

public String getIdByBarcode(String ss) throws SQLException{
    String[] column = new String[]{Pro_ID,Pro_Barcode, Pro_Name,Pro_NameKhmer, Pro_Quantity, Pro_Price, Pro_Description, Pro_Date};
    Cursor c = ourDatabase.query(TABLE_NAME, column, Pro_Barcode + "= '" + ss + "' " , null, null, null, null);

    if(c != null){
        c.moveToFirst();
        String id = c.getString(0);
        Log.v(id, id + "Id" );
        return id;
    }
    return null;
}

回答1:

No results in the Cursor. You should check what moveToFirst() is returning (most likely false). Also you should use moveToNext(), not moveToFirst(). Also watch out that you're not checking ss parameter. This could lead to SQL injection vulnerabilities. You should be using parameters. Also I think you can use a single return in your method.

public String getIdByBarcode(String ss) throws SQLException {
    String[] column = new String[]{Pro_ID,Pro_Barcode, Pro_Name,Pro_NameKhmer, Pro_Quantity, Pro_Price, Pro_Description, Pro_Date};
    final String args = new String[1];
    args[0] = ss;
    Cursor c = ourDatabase.query(TABLE_NAME, column, Pro_Barcode + " = ?" , args, null, null, null);
    String ret = null;
    if(c.moveToNext()) {
        ret = c.getString(0);     
    }
    return ret;
}

回答2:

The literature of moveToFirst() method:

public abstract boolean moveToFirst () Move the cursor to the first row. This method will return false if the cursor is empty.

Returns whether the move succeeded.

So your moveToFirst call is failing(because cusrsor has 0 elements) and that is the reason for crash.

Do this:

if(c != null && c.moveToFirst()) {
    String id = c.getString(0);
    Log.v(id, id + "Id" );
    return id;
}

回答3:

try this

String id;
if (c!= null && c.moveToNext){
   String id = c.getString(0);
   return id;   
 }