I am using Xamarin.iOS. I have created UIView with a few UITextFields. I am looking for best way to initialize text value in these textfields from code.
I can pass text data in the constructor of UIViewContoller, but I don't have access to textFields inside it (they are null). I can change text value of textFields in viewDidLoad method.
I don't want to create additional fields in controller class to store data passed by constructor and use them in viewDidLoad. Do you know better solution ?
I don't want to create additional fields in controller class to store
data passed by constructor and use them in viewDidLoad.
But that's how it's meant to be done.
Alternatively, you can create less fields/properties in your viewcontroller if you use a MVVM pattern:
public class UserViewModel {
public string Name { get; set;}
public string Title { get; set;}
}
public class UserViewController : UIViewController
{
UserViewModel viewModel;
public UserViewController (UserViewModel viewModel) : base (...)
{
this.viewModel = viewModel;
}
public override void ViewDidLoad ()
{
userName.Text = viewModel.Name;
userTitle.Text = viewModel.Title;
}
}
That's the kind of pattern which gives you a lot of code reuse accross platforms (android, WP, ...) and clearly separate concerns. It's a (very) little bit of extra code, but it's worth every byte.
Related
I have a button in View "A" which already has a bindingSet attached to it (it binds to ViewModel "A"). I have button though which needs to be bound to ViewModel "B".
What is the best way to do this?
Your ViewModel is your Model for your View.
If that ViewModel is made up of parts, then that can be done by aggregation - by having your ViewModel made up of lots of sub-models - e.g:
// simplified pseudo-code (add INPC to taste)
public class MyViewModel
{
public MainPartViewModel A {get;set;}
public SubPartViewModel B {get;set;}
public string Direct {get;set;}
}
With this done, then a view component can be bound to direct sub properties as well as sub properties of sub view models:
set.Bind(button).For("Title").To(vm => vm.Direct);
set.Bind(button).For("TouchUpInside").To(vm => vm.A.GoCommand);
set.Bind(button).For("Hidden").To(vm => vm.B.ShouldHideThings);
As long as each part supports INotifyPropertyChanged then data-binding should "just work" in this situation.
If that approach doesn't work for you... In mvvmcross, you could set up a nested class within the View that implemented IMvxBindingContextOwner and which provided a secondary binding context for your View... something like:
public sealed class Nested : IMvxBindingContextOwner, IDisposable {
public Nested() { _bindingContext = new MvxBindingContext(); }
public void Dispose() {
_bindingContext.Dispose();
}
private MvxBindingContext _bindingContext;
public IMvxBindingContext BindingContext { get { return _bindingContext; } }
public Thing ViewModel {
get { return (Thing)_bindingContext.DataContext; }
set { _bindingContext.DataContext = value; }
}
}
This could then be used as something like:
_myNested = new Nested();
_myNested.ViewModel = /* set the "B" ViewModel here */
var set2 = _myNested.CreateBindingSet<Nested, Thing>();
// make calls to set2.Bind() here
set2.Apply();
Notes:
I've not run this pseudo-code, but it feels like it should work...
to get this fully working, you will also want to call Dispose on the Nested when Dispose is fired on your View
given that Views and ViewModels are normally written 1:1 I think this approach is probably going to be harder to code and to understand later.
I have a class CalculationManager which is instantiated by a BackgroundWorker and as such has a CancellationRequested property.
This CalculationManager has an Execute() method which instantiates some different Calculation private classes with their own Execute() methods which by their turn might or might not instantiate some SubCalculation private classes, in sort of a "work breakdown structure" fashion where each subclass implements a part of a sequential calculation.
What I need to do is to make every of these classes to check, inside the loops of their Execute() methods (which are different from one another) if some "global" CancellationRequested has been set to true. I put "global" in quotes because this property would be in the scope of the topmost CalculationManager class.
So, question is:
How can I make a property in a class visible to every (possibly nested) of its children?
or put down another way:
How can I make a class check for a property in the "root object" of its parent hierarchy? (well, not quite, since CalculationManager will also have a parent, but you got the general idea.
I would like to use some sort of AttachedProperty, but these classes are domain objects inside a class library, having nothing to do with WPF or XAML and such.
Something like this ?
public interface IInjectable {
ICancelStatus Status { get; }
}
public interface ICancelStatus {
bool CancellationRequested { get; }
}
public class CalculationManager {
private IInjectable _injectable;
private SubCalculation _sub;
public CalculationManager(IInjectable injectable) {
_injectable = injectable;
_sub = new SubCalculation(injectable);
}
public void Execute() {}
}
public class SubCalculation {
private IInjectable _injectable;
public SubCalculation(IInjectable injectable) {
_injectable = injectable;
}
}
private class CancelStatus : ICancelStatus {
public bool CancellationRequested { get; set;}
}
var status = new CancelStatus();
var manager = new CalculationManager(status);
manager.Execute();
// once you set status.CancellationRequested it will be immediatly visible to all
// classes into which you've injected the IInjectable instance
I need to set an event handler on objects that get instantiated by OrmLite, and can't figure out a good way to do it short of visiting every Get method in a repo (which obviously is not a good way).
To give some background - say I have a class User, which is pulled from database; it also implements INotifyPropertyChanged. I want to assign a handler to that event. Having it auto-populated from Funq would be ideal, but of course OrmLite doesn't ask Funq to hydrate the new object.
So I'm stuck.
Any hints in a right direction would be appreciated.
It sounds to me like you're mixing in presentation logic with your data access logic. If I was in your position I would not attempt to implement INotifyPropertyChanged on a model (such as your User class). Instead I would create a ViewModel and place the databinding logic there (MVVM Style).
Having INotifyPropertyChanged on the data model is not quite logical when you get down to it. If I were to update the database record it would not fire this event for example (but the property has changed). It makes a lot more sense on a ViewModel.
Beyond solving your original issue it also makes building complex screens a lot easier by letting you aggregate, compose, and filter data for display purposes. If you need to pull in information from your database, a RSS feed, a stock ticker web API, and twitter you can do so in your ViewModel.
public class User
{
[AutoIncrement]
public int Id { get; set; }
public string Name { get; set; }
}
public class UserViewModel : INotifyPropertyChanged
{
private string _name;
public UserViewModel(User user)
{
_name = user.Name;
}
public string Name
{
get { return _name; }
set {
if (value == _name) return;
_name = value;
OnPropertyChanged("Name");
}
}
public event PropertyChangedEventHandler PropertyChanged;
[NotifyPropertyChangedInvocator]
protected virtual void OnPropertyChanged(string propertyName)
{
if (PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
Small Note: This answer was written in the context of display data on a screen with a ViewModel, however, the same concept applies to observing model changes for any purpose.
When accessing to outlets from my CustomClass : UICollectionViewCell, they are appearing as not initialized and can not set a proper value.
Every example I've seen it uses a plain Class (no XIB) to set the UI.
[Register("CustomCommentCell")]
public partial class CustomCommentCell : UICollectionViewCell
{
public static readonly NSString Identifier = new NSString("CustomCommentCell");
public CustomCommentCell () : base()
{
}
public CustomCommentCell (IntPtr handle) : base (handle)
{
}
public void updateData()
{
this.lblComment.Text = "Test";
}
}
On the other hand, I have registered the Class:
this.tableComments.RegisterClassForCell (typeof(CustomCommentCell),commentCellId);
and have the GetCell properly set.
However, when trying to set the outlets to a specific value, it indicates it is null. (this.lblcomment = null) while it should have been a UILabel initialized.
Any clues?
to create the Custom CollectionViewCell using XIB. do the following
1) create C# class which inherits from UIcollectionViewCell
[Register("MyCustomCell")]
public class MyCustomCell : UICollectionViewCell
{
public static readonly NSString Key = new NSString ("MyCustomCell");
[Export ("initWithFrame:")]
public MyCustomCell(CoreGraphics.CGRect frame) : base (frame)
{
}
public override UIView ContentView {
get {
var arr= NSBundle.MainBundle.LoadNib ("MyCustomCell", this, null);
UIView view =arr.GetItem<UIView> (0);
view.Frame = base.ContentView.Frame;
base.ContentView.AddSubview (view);
return base.ContentView;
}
}
}
2) Add a IphoneView XIB file has the Same Name as that of Class created in step 1
3) Open XIB in XCODE and do the Following Changes
3.1)Select the FileOwner set the Class same name as Step 1
3.2)Select The View Set the Class name UIView
4) Design Your XIB Accordingly
I can't follow quite the problem you are seeing. What is a "Custom XIB outlet"? Why is this question tagged "custom-controls"? Is there some example code or pictures you can show to help explain the problem?
The approach I use for UICollectionViewCell's is the same as I use for UITableViewCell - see the tutorial - http://slodge.blogspot.co.uk/2013/01/uitableviewcell-using-xib-editor.html
Update: From the code you've posted as a comment (not sure if it's complete or not), I think it would be useful for you to follow through that tutorial. There are a few steps to complete including registering the custom class name and including using RegisterNibForCellReuse - one of those will probably fix this for you.
I am using a custom UITableViewDelegate and in my controller I want to run some code when the tableview has a rowselected. I noticed the UITableViewDelegate already has an event called RowSelected but you cannot use it I'm guessing because there is a method in UITableViewDelegate with the exact same name.
If I write:
mytableviewdelegate.RowSelected += myeventhandler;
This will not compile and gives the error:
"Cannot assign to 'RowSelected' because it is a 'method group'"
Any ideas, I have a work around which is fine so Im really looking at working out if this is a bug in MonoTouch?
How are you implementing the custom UITableViewDelegate? I would suggest using Monotouch's UITableViewSource as it combines both the UITableViewDataSource and the UITableViewDelegate into one file which makes things so much easier.
Some example code:
(in your UIViewController that contains the UITableView)
tableView.Source = new CustomTableSource();
Then you'll want to create a new class for this:
public class CustomTableSource : UITableViewSource
{
public CustomTableSource()
{
// constructor
}
// Before you were assigning methods to the delegate/datasource using += but
// in here you'll want to do the following:
public override int RowsInSection (UITableView tableView, int section)
{
// you'll want to return the amount of rows you're expecting
return rowsInt;
}
// you will also need to override the GetCells method as a minimum.
// override any other methods you've used in the Delegate/Datasource
// the one you're looking for in particular is as follows:
public override void RowSelected (UITableView tableView, NSIndexPath indexPath)
{
// do what you need to here when a row is selected!
}
}
That should help you get started. In the UITableViewSource class you can always type public override and MonoDevelop will show you what methods are available to be overriden.