I am using TabBar in my application where I need to get Input in first tab and show
output based on some calculation on other tab.
I am able to get input in first tab but when I click on second tab, my state is lost. I am not sure if I have to make it a Stateful widget at root level.
I am relatively new in Mobile App. Can someone help me out here?
EDIT:
Now I am able to achieve what I said above, but when I am trying to access the list of items from first tab, it throws null exception in second tab?
I solved the above problem using AutomaticKeepAliveClientMixin as described in the answer below.
I think what you may be after is AutomaticKeepAliveClientMixin. I always add that to my screen widgets within TabBarView. This way when a user enters data into fields in one tab and navigates to other tabs and back the data is still there as you would expect.
Then when the user performs an action like "save" I deal with state management (BLoC etc).
You may want to use architecture for managing and sharing states. There are many approaches to manage state:
InheritedWidget to pass app state down the widget hierarchy
Scoped model library to hold app state and notify Widgets of Updates
Redux library to manage app state and update Widgets
Business Logic Components (BLoC)
Check out this article. Check this GitHub repository with different architecture examples
Related
How do I save the state of a dismissible? When the item is dismissed it stays dismissed upon closing and opening the app?
I'm relatively new to flutter and checked out saved preferences plugin but couldn't get it to work.
You need some way to persist and restore the state of the application between launches. A common solution in Flutter is to use Redux, which is a unidirectional data flow architecture for managing state. This blog post from Xavi Rigau is quite a good introduction.
There is an example app in the GitHub repository that extends the default counter example app to use redux.
In order to persist the state between app launches, you'll need to add the persistence layer. One option would be to use your own file storage middleware (see Xavi's post and the examples in the flutter_redux repository). Another approach would be to use the Flutter redux_persist library (I haven't used this one yet).
Note: Given the complexities and details involved, I haven't included code examples here, but there is plenty in the listed references.
I've written an extension for VSTS/TFS which adds a context menu for creating child work items.
The creation of the work items works well, but the change is not reflected in the Grid/Board until I perform a Refresh of the entire page.
Is there a way to refresh just the affected work items (somewhat similar to the refresh performed by the '+' menu item)?
There isn't any way to achieve this. If you open two pages and click "+" button to add two different child workitems from the two pages in the same time, you will find that the affected work item is not real refreshed, it just show the new added one. And you cannot control the behavior on Grid/Board either since the VSTS extensions are hosted in iframe which is cross-origin.
As far as I know this is currently not possible.
I struggled with that question for quite some time before I gave up and just told my users to hit F5 after creating the new work items. The NavigationService is the best alternative i know of.
For your specific case, this doesn't help you. However, if anyone runs across this question looking for ways to refresh a work item, you can use the work item form service method "refresh":
https://www.visualstudio.com/en-us/docs/integrate/extensions/reference/client/api/tfs/workitemtracking/services/workitemformservice#refresh
This service is a means to interact with the currently active work item form. So, this refresh will work on a work item that the user has opened.
I'm new in Rails, I have a Meal model which has many Products. Meals are assign to User (maybe this is important for a concept). In meals/new.html.erb I want to create new Meal as follow:
Click the button "Display Products"
On the same page (meals/new.html.erb) open modal (pop-up) with all products assigned to current user ( I have help method for current-user). It should be displayad like a list or grid with checboxes for example.
Then user can check few products and click "Confirm".
After that in meals/new.html should be appeared list of chosen products with additional input to fill their quantity.
So I have two problem here.
How should I display modal? Is needed any Ajax (I'm not so familiar with this technology)
How can I pass products between view and modal?
Could you help me a little to achieve these goals?
Regarding your first problem, displaying the modal is fairly straight forward. Essentially you will create a div with the proper bootstrap classes to be hidden when the page is loaded, and then create a button that makes it visible. I would recommend either reading over the W3Schools entry on modals, or from the appropriate part of the bootstrap javascript documentation.
Regarding your second question, this depends on exactly what you mean. The modal is part of the view, so if you're only trying to put information that is currently on the modal back onto the "page" behind it, you can do so fairly simply with javascript (copying content out of one element into another, or updating states of inputs). If, on the other hand, you're trying to use the modal to retrieve information from the server (for instance if you wanted to show a list of possible options, and then display detailed information about the selected items from the database) that would require Ajax.
If you have any snippets of code that aren't functioning as you expect, feel free to add your View to the question. In cases like this, usually the best way for us to provide help is for you to take an early crack at this, post the relevant code, and then seek answers for the things that behave unexpectedly.
I hope that helps.
I am using Durandal, knockout to create a Single Page Application. I need to do following (two pretty simple things):
Show/hide widgets that are only for administrator, based upon the user's authorization,
Change menu options based upon whether user is authenticated or not (for anonymous show - login/sign up and when authenticated show "Welcome .." .
If this was a regular MVC4 application I would have done it using
#if (User.Identity.IsAuthenticated) { ... } check in razor views, but with views in durandal this is ruled out.
I want to avoid putting sensitive business logic in javascript - user need not know what kind of options could have been available to him if he was an administrator.
What's the best way to achieve this in Durandal & Knockout? I have been coding so far using classic ASP.NET and lately using ASP.NET MVC. Developing SPA using Durandal is a new game for me...If anyone can give me only steps/pointers to do this that will help a lot too..thanks in advance!
The way I do it.
My menus are build inside a menubar.js file. The menuItems are observableArrays([]) initially and I subscribe to a topic "user-logged-in".
When the user logs in, I get the user's permissions/roles and store them locally in storage. and then send out notification "user-logged-in" with the user data.
My menubar recieves the notification, checks the permissions/roles and adds various menu items appropriately.
the shell.html has a view composition for the menubar.js. So if there are menuitems, it shows up, else it does not. so when the user logs in, the menuItems are populated and at this point the menu items show up.
When the user logs out, I clear the local storage cache and send out a message "user-logged-out".
The menubar.js recieves this message and clears it's menu items, essentially clearing the menu on the menubar.htm
You can essentially do the same for the widgets and use a visible binding to a property which hides or shows for a particular permission/role.
Also important is router.guardRoute. read up on this so that people cannot directly go to a route without logging in.
Hope that helps
I want to modify the django admin for a particular model to provide the following behaviour.
A user make a search on the change_list page. The the user click a specific entry and he lands on the change_form for that entry. Nothing different to the usual.
Now, what I want is a mean to navigate the former search results. Basically next and previous buttons on the edit page.
What would be the best approach to implement this feature without modifying the admin site too much?
I will need to memorize the search in the user session, then when an entry is clicked I will need to known which place it has within the results to place my "cursor" accordingly. But I'm a bit in the cloud as the implementation side.
One way is to just put the next and previous button in the template for that particular model.
This can be implemented using simple javascript.
I ended writing a fully custom admin for that.