I wanted to save the information, during the view change.
When I go from one view to another view, I Be Lost the load information of the opposite view.
How can i keep the information or how can i keep the view
I use in my application that source code
http://www.programcreek.com/java-api-examples/index.php?source_dir=java_learn-master/vd7_learn/src/main/java/com/mycompany/MyVaadinUI.java
Thank you in advance
According to your code, you provide View for navigator as class, so it creates new instance of class on each navigation.
You should use addView with instance of your class.
Example:
getNavigator().addView("page1", new PageView());
I believe you need to save the information in the VaadinSession.
In view1, do this:
UI.getCurrent().getSession().setAttribute("param_name", "param_value");
In view 2, do this:
String param_value = UI.getCurrent().getSession().getAttribute("param_name");
param_value could be instance of any class.
Related
why is this error happening and what can i do to fix/prevent in the future? thanks!
NOTE: my other class is set up as such:
class Other {
//then all relevant funcs called
}
am i missing some basic setup information in order for this to run?
The formal explanation would be:
You're trying to access the view property before it was initialized. Another way to look at it is that you're trying to access the view property before it was loaded (in viewDidLoad).
Solution:
Depends what you're using that view for. I've never had to access another view controller's property like that. Consider exploring other strategies such as delegation, weak references to another controller, and passing variables in prepareForSegue if you need a reference from a view controller from another.
I found a view is somehow added under the control of a view controller, how can I track this process while debugging? My goal is to find where and how this view is created and added so that I could remove it since I don't need this view. Thanks.
You can use the Debug View Hierarchy:
Here you can see al the views, find the one you' re looking for, select it and select Show the Object Inspector:
There you will see the memory address of the object, in my case I've selected a UILabel, then you can add a watch expression on the debug area by right clicking:
Write the address casted to your view element (again, in my case a UILabel):
((UILabel*) 0x14ff9c80)
Finally, you will see something like this:
With this you will be able to get some information of the view you're looking for.
You can create a custom subclass for your self.view in UIViewController and override addSubview and insertSubview:atIndex and put breakpoints there.
All added views then should trigger a breakpoint.
I have created a timer class in swift and when a user clicks a button I segue to another view and pass data between the two views. The time class uses 3 separate labels for hour, minute and second however I would like to pass all 3 in a single variable.
My question is, how do I access the text inside a label. If I use "\(hourLabel.text)" (for example) I get a message "Optional(00)".
If you're trying to access another view controller's view objects (a UILabel, for example) don't do that. It violates the principle of encapsulation, and also often doesn't work.
If try to evaluate hourLabel.text where hourLabel is an outlet in your current view controller, the outlet link is probably broken (and nil.)
Post the actual code you are trying to use.
Use this...
if hourLabel.text != "" {
println("\(hourLabel.text!)")
}
Why don't you try this...
if(!hourText.text){
// Do something...
}
I have 2 viewControllers (NewTicket1Controller and NewTicket2Controller). View 1 has a text field named 'ticket' and view 2 wants to access that value.
Here is my code in View 2.
NewTicket1Controller *screen1 = [[NewTicket1Controller alloc] init];
NSLog(#"%#", screen1.ticket.text);
My NSLog statement above returns null for the ticket textfield value. But it's not null. If I switch back to view 1 I can see that there is a value in that field.
Can I not retrieve a variable like this?
When you instantiate a new NewTicket1Controller, all of it's properties are initialized to their default values. This does not give you a reference to any existing NewTicket1Controller objects. If you are using storyboards, you can pass it to the other view controller in prepareForSegue, or if you are not using storyboards, you can programatically pass it to the new view controller when it is created, assuming it is created from the NewTicket1Controller.
No need to initialize you view to access it. If you want to send text contained in textfield to another view..You need to store that ticket text field value into a string of other view controller..
At NewTicket2Controller take property with NSString with name ticketString and synthesize it...Then you can use that reference for storing value of ticket at NewTicket1Controller
At button action while switching to NewTicket2Controller..Put some code at NewTicket1Controller
NewTicket2Controller *screen2 = [[NewTicket2Controller alloc] initWithNibName:#"NewTicket2Controller" bundle:nil];
screen2.ticketString=self.ticket.text;//if you propertise the ticket textfield
NSLog(#"%#", screen2.ticketString);
Hope it helps you..
You just created and inited screen1. Any and all values will be nil or initialized.
A few things:
You want to try to keep the data (model) separate from your views and controller when possible.
You're going to have to provide some connection between the 2 view controllers.
One approach is to set up one as a weak link to the other.
Example for NewTicket2Controller
#property (nonatomic, weak) NewTicket1Controller *delegate;
And then when you create NewTicket2Controller you would assign self.delegate = screen1
After that you could access methods using the delegate.
(Ideally you'd setup a protocol for the delegate)
Others have given you partial answers. Let me state everything at once.
First, never try to manipulate another view controller's view objects directly. That is serious violation of the "encapsulation" principle of object oriented programming. You should treat a view controller's views as private, and add properties or methods to communicate between view controllers.
Second, you are creating a brand new instance of your view controller and expecting to be able to use that new view controller instance to alter settings in an existing view controller. This is like buying a new car that is a perfect match for your existing car, setting the radio station on that new car, and then wondering why the radio station on the old car doesn't change. They are different cars! They are different objects! They may be feature-for-feature identical, but they are different instances of the same object. If you had an identical twin, it is still a different person, right?
You need a way to get a pointer to your existing NewTicket1Controller object. How you do that depends on how your program is set up. Post some info on how you are setting up your view controllers. Are you using a navigation controller? Is NewTicket1Controller your root view controller? How are you getting from view controller 1 to view controller 2? A segue? (assuming you're using storyboards. Tell us if you're not.)
I am trying to build a MVC app with Objective-C. It is supposed to be a questionnaire app. I have all the questions and multiple choice answers stored into a property list, because I have different of questionnaires that I want to be able to load with this app. The idea is that the main model will keep track which item it should read of the property list, and select the corresponding view and viewController.
So schematically I have the following problem.
The RootView shows the start menu, that selects which questionnaire you will be able to take.
The RootViewController is the first controller called by the app delegate. It is supposed to instantiate the model and show the RootView. It furthermore controls the buttons of the RootView.
The model is supposed to wrap the items of the property list into a fitting datastructure, and supply it to the view controllers that need it.
The SelectedViewController is a controller that is a template specifically made for a type of question. The question could be a multiple choice, an open question, a 3, 5 or 7 choice likert scale kind of question, anything really. The template name that these view controllers will really get is ViewController.
The SelectedView is a tailor made view to the question type and will get the same name format as all the selected view controllers.
Here are my ideas.
My initial hunch is to use the delegate pattern, and set the model as a delegate to any SelectedViewController.
I could also use the delegate pattern to the RootViewController, and let him monitor if the SelectedViewController should be destroyed (via a delegate message). In that case, I can implement a prepareForSegue in the RootViewController to the SelectedViewController.
Since it is a questionnaire from a plist I could also add a prepare for segue to
every selected viewcontroller, but that will probably be a problem,
since there are at least 15 different ways of displaying the
questions.
Apparently there is also something like Key-Value Observing, according to this question. So that's also something I could use.
I think there is a definite way to deal with this, because the design patterns in iOS are pretty wel described, so there should be a few options for this really (or only just one). At the moment I am leaning towards setting the RootViewController as a delegate to the SelectedViewController and let the RootViewController handle the model. In this way I am extending the RootViewController to also hold all common functionality that every SelectedViewController should have.
But I am really not sure if this is the way to go, because my knowledge on design patterns is limited. My question is: what is the right option to choice in this specific situation (e.g. views and view controllers selected via a .plist file)?
There is no need for a specific pattern - you can deal with accessing an instance of a model object by name, i.e. in the same exact way that you deal with making a specific view and the view controller.
Let's say you are looking to connect the QuizQuestionViewController4MC and its QuizQuestionView4MC to their model. Let's assume that the model class is called QuizQuestionModel4MC, and that it needs to be configured with an object that you get from a key #"4MC" in the plist. Since your code learns the name of the model class only at runtime, you can create an instance using reflection:
NSDictionary *dataFromPlist = ... // Someone passes this to you
NSString *identifier = dataFromPlist[#"identifier"]; // Returns #"4MC"
NSString *ctrlName = [NSString stringWithFormat:#"QuestionViewController%#", identifier];
NSString *modelClassName = [NSString stringWithFormat:#"QuizQuestionModel%#", identifier];
id model = [[NSClassFromString(modelClassName) alloc] init];
// Configure the model with the data from plist
[model setPlistData:dataFromPlist];
// The model is ready to be used - give it to the view controller
MyBaseViewController *ctrl = [storyboard – instantiateViewControllerWithIdentifier:ctrlName];
// Give the view controller its model - now it is ready to be used
[ctrl setModel:model];
Note the class of the view controller - MyBaseViewController. This is not your root view controller, it's a base class for all your specific view controllers. It is this view controller that knows about a model, but it does not know the specific subclass in the model hierarchy. Each subclass of the view controller knows about its specific model subclass, so it can access the information from the model class directly, without going through selectors or KVP.
Of course it is up to the designer of the app to "wire up" correct view controllers to the correct models. In terms of the above example, QuizQuestionViewController4MC needs to know the structure of the QuizQuestionModel4MC in order to avoid sending unrecognized selectors to an incorrect class.