We're using gwt-presenter, but not really a question specific to that...
I've got a table with users in it. As I build the table in the view (from the data provided by the presenter), I need to add two action buttons ("Edit", and "Delete") at the end of the row.
What's the best way to assign click handlers to these buttons so the presenter knows which was clicked? Previous to this, we could pass a private field from the view to the presenter and attach a discrete click handler to that button. However, this method is rather rigid and doesn't work in this scenario very well.
Thanks in advance.
How about having the view allowing the subscription for edit/delete click events, registering internally the individual row click events, and then delegating the event handling to the ones registered by the view?
I mean something like the following pesudo code:
View:
addRowEditClickHandler(ClickHandler handler) {
this.rowEditClickHandler = handler;
}
addRowDeleteClickHandler(ClickHandler handler) {
this.rowDeleteClickHandler = handler;
}
//... somewhere when setting up of the grid...
rowEditButton.addClickHandler = new ClickHandler() {
onClick(args) {
this.rowEditClickHandler.onClick(args)
}
rowDeleteButton.addClickHandler = new ClickHandler() {
onClick(args) {
this.rowDeleteClickHandler.onClick(args)
}
Presenter:
View view = new View();
view.addRowEditClickHandler( new ClickHandler() {
onClick(args) {
doSomething();
}
});
view.addRowDeleteClickHandler( new ClickHandler() {
onClick(args) {
doSomething();
}
});
Related
So, I have a listview and I want it whenever an item is created to scroll to that item (bottom). Because I am using MVVM I found really nice explanation on how to make a new control that inherits from listview that scrolls down. The problem is that this answer (the third) is referring to WPF 6 years ago.
I am making a UWP app, so I copied the code and tried to format it to my needs. The following code doesn't give any error or exception but instead it loads the "ChatListView" as I call it perfectly and then does nothing. The comments are only a bit edited compared to the original code.
What can I do ? Thank you in advance!
public class ChatListView : ListView
{
//Define the AutoScroll property. If enabled, causes the ListBox to scroll to
//the last item whenever a new item is added.
public static readonly DependencyProperty AutoScrollProperty =
DependencyProperty.Register(
"AutoScroll",
typeof(Boolean),
typeof(ChatListView),
new PropertyMetadata(
true, //Default value.
new PropertyChangedCallback(AutoScroll_PropertyChanged)));
//Gets or sets whether or not the list should scroll to the last item
//when a new item is added.
public bool AutoScroll
{
get { return (bool)GetValue(AutoScrollProperty); }
set { SetValue(AutoScrollProperty, value); }
}
//Event handler for when the AutoScroll property is changed.
//This delegates the call to SubscribeToAutoScroll_ItemsCollectionChanged().
//d = The DependencyObject whose property was changed.</param>
//e = Change event args.</param>
private static void AutoScroll_PropertyChanged(
DependencyObject d, DependencyPropertyChangedEventArgs e)
{
SubscribeToAutoScroll_ItemsCollectionChanged(
(ChatListView)d,
(bool)e.NewValue);
}
//Subscribes to the list items' collection changed event if AutoScroll is enabled.
//Otherwise, it unsubscribes from that event.
//For this to work, the underlying list must implement INotifyCollectionChanged.
//
//(This function was only creative for brevity)
//listBox = The list box containing the items collection.
//subscribe = Subscribe to the collection changed event?
private static void SubscribeToAutoScroll_ItemsCollectionChanged(
ChatListView listView, bool subscribe)
{
INotifyCollectionChanged notifyCollection =
listView as INotifyCollectionChanged;
if (notifyCollection != null)
{
if (subscribe)
{
//AutoScroll is turned on, subscribe to collection changed events.
notifyCollection.CollectionChanged +=
listView.AutoScroll_ItemsCollectionChanged;
}
else
{
//AutoScroll is turned off, unsubscribe from collection changed events.
notifyCollection.CollectionChanged -=
listView.AutoScroll_ItemsCollectionChanged;
}
}
}
//Event handler called only when the ItemCollection changes
//and if AutoScroll is enabled.
//sender = The ItemCollection.
//e = Change event args.
private void AutoScroll_ItemsCollectionChanged(
object sender, NotifyCollectionChangedEventArgs e)
{
if (e.Action == NotifyCollectionChangedAction.Add)
{
int count = Items.Count;
ScrollIntoView(Items[count - 1]);
}
}
//Constructor a new ChatListView.
public ChatListView()
{
//Subscribe to the AutoScroll property's items collection
//changed handler by default if AutoScroll is enabled by default.
SubscribeToAutoScroll_ItemsCollectionChanged(
this, (bool)AutoScrollProperty.GetMetadata(typeof(ChatListView)).DefaultValue);
}
}
If you want to create a chat application you can use the ItemsStackPanel's ItemsUpdatingScrollMode particular property to KeepLastItemInView value to scroll to the latest item.
Usage:
<ListView>
<ListView.ItemsPanel>
<ItemsPanelTemplate>
<ItemsStackPanel ItemsUpdatingScrollMode="KeepLastItemInView" />
</ItemsPanelTemplate>
</ListView.ItemsPanel>
</ListView>
Note: KeepLastItemInView enum member was introduced in the 14393 SDK.
Related link:
https://learn.microsoft.com/en-us/uwp/api/Windows.UI.Xaml.Controls.ItemsStackPanel#properties_
The accepted answer is pretty nice. However I there is one thing it won't do (at least if I simply copy and paste the above XAML): it won't do its intended scrolling if, say, the user was away from that page while new items were added, and then they navigated to the page.
For that I had to hook into
protected override void OnNavigatedTo(NavigationEventArgs e)
{
base.OnNavigatedTo(e);
if (MyListView.Items.Count == 0)
return;
object lastItem = MyListView.Items[MyListView.Items.Count - 1];
MyListView.ScrollIntoView(lastItem);
}
Our designer created a layout something like the screen above. The main idea was to create an application with only one screen, just the red part of the screen is changing (i.e. 2 textbox instead of 1 textbox) when you tap on a button. This application will be a multiplatform application and I'm using MvvmCross to create it. My question is that how can i achieve this behavior in Mvvm? My first thought was sg. like the code below, but I'm not satisfied with this solution. Do you have any better solution to this problem? Should i somehow overwrite default navigation on ShowViewModel()?
public class MainViewModel : MvxViewModel
{
private MvxViewModel _currentViewModel;
public MvxViewModel CurrentViewModel
{
get { return _currentViewModel; }
set { _currentViewModel = value; RaisePropertyChanged(() => CurrentViewModel); }
}
public MainViewModel()
{
CurrentViewModel = new DefaultViewModel();
}
public void OnButtonClick()
{
CurrentViewModel = new SecondViewModel();
}
}
public partial class MainViewModel : MvxViewController
{
public override void ViewDidLoad ()
{
base.ViewDidLoad ();
FirstViewModel.WeakSubscribe(ViewModelPropertyChanged);
}
private void ViewModelPropertyChanged(object sender, PropertyChangedEventArgs args)
{
if (args.PropertyName == "CurrentViewModel")
{
if (Model.CurrentViewModel != null)
{
if (Model.CurrentViewModel is SecondViewModel)
{
//remove bindings
//change View
//bind new viewmodel
}
}
}
}
The alternatives for this kind of 'non-page navigation' are similar to those in MvvmCross Dialog:
You can:
Customize the MvxPresenter to allow ShowViewModel to be used
Put a special interface in the Core project and use Inversion of Control to inject the implementation from the UI project to the Core project
Use the MvxMessenger plugin and share messages between the Core and UI project which trigger this type of navigation.
Use a property with a special interface (like IInteractionRequest) on the ViewModel - that property will fire an event when the UI needs to change.
Personally, for your situation, I quite like the first of these options - intercepting ShowViewModel using a presenter.
One other alternative which I might consider is to use some kind of 'Adapter-driven' control which could very easily update it's child contents based on the CurrentViewModel property. On Android, this would be as easy as using an MvxLinearLayout with an adapter. On iOS, however, I think you'd have to write something new to do this - just because iOS doesn't really have a LinearLayout/StackPanel control.
I want to implement menu in GWT as shown on this website:
http://www.openkm.com/en/
I have created the menu system and I am able to display alerts from menu using following code:
Command cmd = new Command() {
public void execute() {
Window.alert("Menu item have been selected");
}
}
I want to get rid of window.alert() and display my application pages from menu.
Create and load the appropriate page. For example if you use UiBinder then:
MyPage selectedPage = new MyPage(); // creating of your panel
RootPanel.get().clear(); // cleaning of rhe RootPanel
RootPanel.get().add(selectedPage); // adding the panel to the RootPanel
First create an array list of views
public List<UIObject> viewsList = new ArrayList<UIObject>();
Add a view to that list
viewsList.add(addMovieView);
Send the view you want to select to the helper method
public void changeView(UIObject selectedView) {
for(UIObject view : viewsList) {
if(selectedView.equals(view)) {
view.setVisible(true);
} else {
view.setVisible(false);
}
}
}
Are you trying to make the entire page GWT, or just the menu? If it's just the menu, you will need to embed a GWT element into your overall HTML, then call something like
Window.open(linkURL, "_self", "");
from the appropriate menu items, which will navigate to another page.
If i have a GWT composite widget with three text boxes like for SSN, and i need to fire change event only when focus is lost from the widget as a whole, not from individual text boxes how to go about doing that?
If you want just the event when your whole widget loses focus (not the text boxes), then make the top level of your widget be a FocusPanel, and expose the events that it gives you.
You need to implement the Observer Pattern on your composite, and trigger a new notification everytime:
the focus is lost on a specific text box AND
the focus was not transferred to any of the other text boxes.
Couldn't you use a timer? On lost focus from a text box, start a 5ms (or something small) timer that when it hits, will check focus on all 3 TextBox instances. If none have focus, then you manually notify your observers. If one has focus, do nothing.
Put this in your Composite class:
private Map<Widget, Boolean> m_hasFocus = new HashMap<Widget, Boolean>();
And then add this to each one of your TextBox instances:
new FocusListener() {
public void onFocus(Widget sender) {
m_hasFocus.put(sender, Boolean.TRUE);
}
public void onLostFocus(Widget sender) {
m_hasFocus.put(sender, Boolean.FALSE);
new Timer() {
public void run() {
for (Boolean bool : m_hasFocus.values()) {
if (bool) { return; }
}
notifyObservers();
}
};
}
};
.Net Compact Framework
Scenario: User is on a screen. Device can't finds a printer and asks the user if they want to try again. If they click "No", the current screen is closed and they are returned to the parent menu screen. If they click the "No" button multiple times, the first click will be used by the No button and the next click will take effect once the screen has completed redrawing. (In effect clicking a menu item which then takes the user to another screen.)
I don't see a good place to put a wait cursor...there isn't much happening when the user clicks "No" except a form closing. But the CF framework is slow to redraw the screen.
Any ideas?
you can skip pending clicks by clearing the windows message queue with
Application.DoEvents();
We use the following custom Event class to solve your problem (preventing multiple clicks and showing a wait cursor if necessary):
using System;
using System.Windows.Forms;
public sealed class Event {
bool forwarding;
public event EventHandler Action;
void Forward (object o, EventArgs a) {
if ((Action != null) && (!forwarding)) {
forwarding = true;
Cursor cursor = Cursor.Current;
try {
Cursor.Current = Cursors.WaitCursor;
Action(o, a);
} finally {
Cursor.Current = cursor;
Application.DoEvents();
forwarding = false;
}
}
}
public EventHandler Handler {
get {
return new EventHandler(Forward);
}
}
}
You can verify that it works with the following example (Console outputs click only if HandleClick has terminated):
using System;
using System.Threading;
using System.Windows.Forms;
class Program {
static void HandleClick (object o, EventArgs a) {
Console.WriteLine("Click");
Thread.Sleep(1000);
}
static void Main () {
Form f = new Form();
Button b = new Button();
//b.Click += new EventHandler(HandleClick);
Event e = new Event();
e.Action += new EventHandler(HandleClick);
b.Click += e.Handler;
f.Controls.Add(b);
Application.Run(f);
}
}
To reproduce your problem change the above code as follows (Console outputs all clicks, with a delay):
b.Click += new EventHandler(HandleClick);
//Event e = new Event();
//e.Action += new EventHandler(HandleClick);
//b.Click += e.Handler;
The Event class can be used for every control exposing EventHandler events (Button, MenuItem, ListView, ...).
Regards,
tamberg
Random thoughts:
Disable the some of the controls on the parent dialog while a modal dialog is up. I do not believe that you can disable the entire form since it is the parent of the modal dialog.
Alternatively I would suggest using a Transparent control to catch the clicks but transparency is not supported on CF.
How many controls are on the parent dialog? I have not found CF.Net that slow in updating. Is there any chance that the dialog is overloaded and could be custom drawn faster that with sub controls?
override the DialogResult property and the Dispose method of the class to handle adding/remvoing a wait cursor.