I aim to use the native storage plugin to store a potentially large list of objects in Ionic 3. I want to be able to then display the list in an Ionic infinite scrolling list. I presume that if I save the entire list to storage as a single object, with a single key, it will take quite some time to retrieve it, and the list page will remain empty for some time while the list is read asynchronously from storage.
Should I be saving each item in the list with an individual key, such as "key.1", "key.2", "key.3" etc, and then retrieving a "pageful" of items at a time, supported by the infinite scrolling list? The nuisance part of this is that when I want to add a new item to the list, I have to know what key number I'm up to, so I can generate the next key name.
What's the best practice for this scenario? Is there a better way to load a large list from memory asynchronously so that it can be displayed to the user as soon as possible?
I ended up storing my items in a table in a SQLite database, as I wanted to avoid the size limitations that local storage can impose. I use a query like SELECT * FROM submissions LIMIT ? OFFSET ? to fetch a pageful of items at a time from the doInfinite function of an Ionic infinite scroller, keeping track of what page I'm up to and passing that into the OFFSET parameter. The LIMIT argument is the number of rows to fetch for a page, e.g. 10.
This question is to understand how to update any row programatically.
Details.
I have a listcrtl, that accepts the data from either from a file or from the edit controls in the dialog. When the items are added I will know its position, that I added, so I can change its subitem texts. I have even implemented the sort functionality in the list, so now the position keeps changing. I have an identifier column for each row, so that I can recognize the row.
Now, from an out side event, if I have to change an other columns value of an ID that I know , I have to first find the position of the item by comparing the id column, then with that position, I have set the subitemtext.
This works fine except that it takes time to find the row first then it need to update the column.
Now, in order to get the row directly, I need some help.
I have gone through
http://msdn.microsoft.com/en-us/library/windows/desktop/hh298346(v=vs.85).aspx
But this does not use MFC. Please help me achieving this.
If you have many items you should consider switching to Virtual Lists. It is the fastest way to access the data. If you do not want to invest time to this, then the easiest way for you will be the following:
When you populate the CListCtrl store the ID of each item in the item data using the SetItemData() method. The ID will always be associated with the item, even after re-sorting.
When you need to locate the required item, just scan all items, but do not use GetItemText(). Use GetItemData() instead. This will be faster
I have a set of items that are due for people in a system and some items are in a checklist and others are just used for display. I want to get a list of items for display, and a list of items in order for a checklist report showing items still not completed. I was hoping to get some insight on performance and options for ordering items. I could a) add a field "order" as a positive integer and order them by that order number, or b) create a chain object where one item has a next link to the next item in the chain so I can iterate through rapidly.
I guess the second option would require more overhead from the database since it would require a SQL call each time calling item.next, right? The benefit of making a chain would be in resorting the items when I need to make an ordering change.
Any thoughts on performance, and maintainability for which direction I should go? This is a general case question, would it generally be better to use SQL to get the ordering or create a data structure like a chain to iterate?
I've got a spark list that gets dynamically filled.
So far the new items appear at the bottom of the list. What I'd like to do is to add them at the top.
The items in the list have a unique ID so some kind of sorting mechanism would probably do the trick as the new items have a greater ID than the old ones.
What I'd like to avoid is some complex method behind this as I'm working on a mobile platform and the list can get quite big so I need this to be as efficient as possible.
The list's data provider is an ArrayList that gets updated using binding.
How can that be done?
Thanks in advance!
u can Add the items at the starting index of the datagrid. Flex datagrid automatically renew all the indexes and add 1 to all existing element indexes. So
YourDataGridId.dataprovider.addItemAt(item,0) will do.
I have a list of items as a part of a web application. The question is how user can manipulate the order of items in the list (not the list sort order). The typical way is to use arrow buttons to move items up or down. The other way is the drag-and-drop.
But are there any other ways for a user interface for list reordering?
There are two other sorting methods (besides those you mentioned) I've seen which work pretty well.
Click To Move
The method used for ordering items in the Gallery web photo album works pretty well for ordering photos, and it should work just as well for any set that can be represented as a sorted group of clickable elements:
Present your list of items as clickable elements.
Clicking an element "selects" it, it is highlighted to indicate it's selected.
Clicking another item moves the selected item to a position just before the clicked item.
Repeat until all items are in the desired order.
A dummy item is shown at the end of the list for moving items to the end.
This is slightly easier to use than drag-n-drop as it requires less dexterity, and you don't have to hold down the mouse button while you figure out where you want to "drop" the item.
The method could easily be extended to allow selection of multiple items (via shift-click or similar) which could then be placed in a new position in the same way.
Provide Order Numbers
Used by Netflix and some internal apps I've worked with. This works best if your users have a concrete idea of exactly what the numeric order should be (used when working with lists of instruction steps in our internal app).
Present your list of items one per line.
Provide a text entry box next to each item where the order number is displayed, starting with 1.
The user changes the order numbers in the text fields as desired.
If multiple items are given the same order number, they are placed next to each other.
Provide a button to "apply" the sort in JavaScript so that the user doesn't have to submit the entire page to see the re-arranged list. This makes it easy to work in increments.
Edit: A couple of additional thoughts on Drag-and-Drop. You might have used these before or not, but there are a few things that can make drag-and-drop more forgiving and easier to use:
Highlight the area where the item will appear when dropped. For example, show a prominent horizontal line between the two existing items where the item will be inserted if it is dropped.
Ghost the draggable item as it is dragged so that it's obvious what's being moved, rather than using a generic "dragging" cursor. This works best if the items being dragged are still legible if shown on top of one another with transparency.
Make sure the target areas where the draggable can be dropped are sufficiently large. Larger areas can be helpful for people who have trouble with the required coordination.
We've found that drag and drop can be counter intuitive for non-technical people. We have explored the Up Down Arrow which works but can also be cumbersome as you need to keep clicking up and down and it results in a lot of traffic.
Another paradigm we've explored is the Move button so each item in a list has a Move Item button when you click it new buttons are added before and after each item in the list to let you move the item to any location.
This works well when each item in the list takes a lot of space, if each list item is only a single row it can result in a cluttered interface. In our case each item was half a dozen lines of text or more. We also have add item here button before / after each item to allow insertion.
Survey Monkey uses this paradigm as well and inspired some of what we do.
Some thoughts - Very much on the ideas rather than implementation end though...
1 - Provide both up and down arrows and drag and drop, and monitor which is more popular, which type of users use which etc, then tailor from there once you have some data
2 - Add a "random" button which generates the order randomly - could be useless, could be fun depending on your app
3 - Add a "display order" field by the side of each item and allow the user to manipulate it (but make sure that you have some code to auto update the rest of the numbers when one changes) personally I think this could be very confusing, but for some users it might work
4 - Instead of drag and drop in place, have users drag to a new list
5 - For a very simple version, have a "favourite" check box, and then have the list just show the favourites first, (in alphabetical order or something)
6 - Have groups - you assign a group number to an item, all the group ones appear first, followed by group 2 etc
Hope this random rambling has been useful, if i think of anything more I'll come back...
1) A variation of Click to Move would involve having a separate target list, where the user selects the slot into which their item will move, then clicks on the original item to move it.
For example, in the following diagram, the user has already put 'E' at the head of the reordered list and has selected slot three for their next choice. Their next step would be to choose which item from the old list goes into slot three on the new list. (The row of asterisks is a feeble attempt to show that slot three is highlighted or selected.)
old new
----- -----
| A | | E |
| D | | |
| C | |*****|
| | | |
| B | | |
----- -----
Clicking on an item in the new list selects it and highlights its original slot in the old list, which is now a target. Clicking on the item a second time returns it to that original slot.
The new list should also display indicators of some sort to show that it has selectable regions, perhaps unobtrusive (low-opacity) numbered buttons in its slots or some other informative affordance.
2) Another approach would be to allow users to draw lines between the original and desired positions.
Whatever method is chosen, the process need not be chatty: there's no reason this couldn't all be done client side (with the option to save and commit changes to the server).
You can experiment with drag-and-drop using the examples of jQuery UI Sortables.
To make it obvious for the non-technical or new users you could use visual cues such as handles or arrows and maybe a tooltip on hover to suggest dragging the element.
You could even provide an animated gif demonstrating the gesture.
As soon as a user learns how to do this I think it's the easiest method of ordering a list.
Another way is to provide a small text input next to every item, so the user can enter a numerical ordering themselves; then they click a button to reorder it all at once. (I've only seen this used on sites that store the order of items, such as Netflix queue or Livejournal links.)
Sorting, by clicking on headers is very popular. Perhaps only considered as a reordering of the view of the actual list, though.
Implement a copy/paste style function? This would mean you can take an item out of the list, and then select another item, and click "paste" or CTRL+V. This is quite intuitive and would allow large lists to be manipulated easily.
You could implement multi-selection easily to move a large block of adjacent items.
Network traffic would be low (only one or two requests).
You need to make sure the "paste" is consistent. I.e. pasting always inserts above the selected item.
Take a look at Checkvist for more inspiration.
You could also use arrow keys to move up and down.
I actually think the iphone / itouch does this really well when moving application icons.
If you haven't seen it look here: http://www.youtube.com/watch?v=qnXoGnUU6uI
The 'shaking' icons are a very good visual cue that something is moveable/draggable.
So I would suggest this approach with drag an drop. Clicking and holding on an item could put it in 'moveable-mode' and this would be indicated by it shaking (or some easier to code visual cue). Then drag and drop would work in the normal way.
Implementing this in javascript is of course the challenge...
Also another thing to think about - most people make the mistake of conflating usability with learnability. Think who the users of this app are (will they use it regularly and be taught how to use it, or are they public web users who may use it infrequently and not be taught how to use it) - it might give you a different answer to what the solution should be.
To me, performing a drag and drop of list elements in place (i.e. within the list itself) is the best approach.
Not only you can give to your users the immediate idea of what their list will look like (the list is reorganizing before their eyes), but it's also very easy for them to understand the moving mechanism.
And this is the briefest way to have your users ordering the list in the shortest number of moves.
By the way, foreseeing that a list could be longer than few elements, alongside the DnD method you could provide an asynchronous way to order the list: give the user the ability to attribute an ordering number to each entry, and then click on the "Order" button.
Handling in a smart and correct way user's input, this could result in a speed up for longer lists editing.
I was thinking of "Move selected to here":
Let all items be selectable by checkboxes
Let all items have a button or icon meaning "Move selected to here"
When "Move selected to here" is clicked, all selected items are moved to this item in existing order
The edge-cases here are when the items should be moved to either end of the list. One way to solve that, is to move all selected items before the target, and reserve a special button/icon at the end to move the selection there.
I've found the following to be the quickest way to allow specifying item order regardless of list size:
1) If user wants to set the order of list/grid items, they click a "Reorder" button.
2) This opens the reordering dialog which can be used with any list or grid.
3) In the dialog, all of the items are shown in their current order in a list on the left. There is an empty list on the right.
4) The user clicks the items in the left list in the desired order. When an item is clicked, it is removed from the left list and placed in the right list in the next position. In a worst case reordering where every item needs a new order, this allows ordering a list of N items with N clicks.
5) The user can then apply the new order or cancel. Applying the order results in the "display order" field in the data being set to the final order of the items in the right list. You can decide if the "Apply" button is only enabled when the left list is empty.
6) Also available in the ordering dialog are the following controls:
a) A button to move all of the items from the left list to the right list maintaining whatever order they are in
b) A button to start over by reloading the left list in its original order and clearing the right list.
c) A button to sort the right list alphabetically (or by date or numerically depending on what the key field is)
d) Drag and drop capability in the right list to manually drag items into order.
e) An index number column in the right list which, if edited, moves the item to that position.
This provides the best of all worlds. If you have a huge list where only a few items need to be moved, move all items over, then drag the few items where desired or enter the desired index. If you have a small-ish list that needs to be completely reordered, just click the items in the desired order. And so on.
I've used this approach for many years and it has been very effective.
You can show 'Up' and 'Delete' buttons just the way Google does for SearchWiki. Most of the people have at least some experience with it now. Most people bother only with 'Upping' their choice. If they do not like a thing, and want to downvote it, removing from the list with help of the abovementioned 'Delete' button will be easier for them
You could show an overlay when hovering over an element. This overlay shows you 4 arrows (n/e/s/w) and u can click and move the element accordingly.
If you are trying to oder items across a grid like facebook's and picasaweb's photo grouping features, then that is about the only way to handle that
if you had 3 columns each with a list of items, clicking on any of the items would move the item either to the left or right, middle column could show option for left or right. you could still allow for dragging and dropping or sorting using the typical functionality for that.