I have a little problem, I need to load some json data to my grid, but I have specifical json format like this:
{"response":[
76297,
{"aid":66132303,"owner_id":30729520,"artist":"Шакира - Танго","title":"So objection!! I don't wanna be the exception to get a bit of your attention... I love you for free and I'm not your mother, but you don't even bother... Objections!! I'm tired of this triangle... GOT DIZZY DANCING TANGO","duration":224,"url":"http:\/\/cs1663.vkontakte.ru\/u17640367\/audio\/ebde4092fde5.mp3","lyrics_id":"2203614"},
{"aid":129159521,"owner_id":23962687,"artist":"Yann Tiersen","title":"Mother's Journey (Ennja Remix)","duration":281,"url":"http:\/\/cs6000.vkontakte.ru\/u97497795\/audio\/fb309491bc82.mp3","lyrics_id":"21301612","album":"21017129"},
{"aid":81267321,"owner_id":673065,"artist":"Hurts","title":"Mother Nature","duration":170,"url":"http:\/\/cs4633.vkontakte.ru\/u673065\/audio\/d329378eb2d2.mp3","lyrics_id":"5693202"}]
}
So the first element of array is number of total records, and others are the records to load.
If I try to load such records to my grid I have empty row at the bottom, what is a solution? Should I use some "custom" reader, how to implement it?
Yes. Most likely you would need to extend standard Json reader (Ext.data.reader.Json) to parse length first and start parsing records from the second item.
Update: It's quite easy to do actually.
First you need to figure our place where standard reader doesn't behave the way you want it to behave. Add traces to standard reader class, to see what's going on. Most likely it will be somewhere around readResponse() method.
Create your own reader class extending standard one. Simple inheritance.
Override method you need with new logic.
ExtJs code is very well written and commented. I found it's quite interesting to read and understand it.
As a side note I would add that this task (extending existing ExtJs code with your functionality) is a huge help to better understand how ExtJs works inside and you will feel much more confortable working with ExtJs after that.
Related
Most of the article's talk about how to work with the forms like <form:form> Spring tags just with one bean(entity), but in my web app I have more then one bean(actually 3 of them, wich is mirror to my data model in DB(MySql)). What I want is to put values for all of the properties in my entities classes from one form(it may be a jsp or xhtml or html, whatever).
So, I'm kinda new in Spring MVC and as far as I know it has backing object which comes with <commandName> tag in <form:form> tag and I suppose to think that it may be just one commandName backing object for each form??
Q: - Could you please tell me how to easily(or direct me to any example's) to fulfil my pleasant headache.
Q: - It also may have something to get attributes in one controller class but by different methods. Do I have to store them in session or request? I'm thinking to have ModelAndView class for store multiple attributes in map and after store them in ModelAndView (in model). What you suggest?
hope you are having a wonderful day!
I'd suggest you investigate the technique detailed here:
http://forum.springsource.org/showthread.php?58993-Need-to-Populate-Form-data-into-multiple-java-beans
Also, I'm wondering if there could be a terminology issue here. Do you mean you actually want to have just one form on your UI, with a lot of inputs, or do you really mean you want it all on one SCREEN or page? I say that as its also possible to have multiple forms on one UI screen and go that route... which in fact might be easier, as you could then break up your processing into multiple controllers.
Another consideration on the above relates to screen design... if you are going to be populating the data for several beans from one screen, potentially that could be a LOT of data and your screen could get very cluttered and hard to read. So from that standpoint it might also be better to consider breaking your input controls up into multiple (related) screens. There is a little more about that at the bottom of the article I linked above.
You can refer: https://stackoverflow.com/a/4986410/1882833
One approach would be to have a seperate class which encapsules the required objects. And then use it as a command to set and get the data.
I'm currently writing an application that plays podcasts. I'm representing all the feeds and the episodes within them as QStandardItem objects within a QStandardItemModel. Right now, I don't have a way to save this model--when the application closes, the feed model goes up in smoke. I looked at using QSettings, but that only works for datatypes that fall under QVariant.
Looking at this post gave me some hope, but I think I'm doing something wrong. I've got the following code in the constructor for my application.
//Expand QVatiant to use QStandardItemModel
qRegisterMetaType<QStandardItemModel>("QStandardItemModel");
That, however, gives me this error at compile time.
/ [...] QtSDK/Desktop/Qt/4.8.1/gcc/lib/QtGui.framework/Versions/4/Headers/qstandarditemmodel.h:424: error: 'QStandardItemModel::QStandardItemModel(const QStandardItemModel&)' is private
Ah. That reminds me of this caveat from the Qt documentation for QMetaType, here.
Any class or struct that has a public default constructor, a public copy constructor and a public destructor can be registered.
So, where do I go from here? Qt is behaving exactly as it should, so this approach won't work. I'm thinking of saving off the model as an xml file, but that seems like a ton of effort. This seems like a pretty common problem--I just don't know where to look for the answer.
Here's the best solution I could come up with: Create a method that saves the model into an XML document, and call it whenever I change the model (e.g. add or remove a podcast). I don't have the actual source code on hand, but since there's no real easy way to save the data structure wholesale, this is the best solution.
I asked this question to get some opinions on the subject of glue code.
For example, imagine you have a class (pseudocode):
class MyClass
int attribute a
string attribute b
And to represent that data model, you have BOTH a slider and a text box to represent a, and a text box and say... the window label to represent b.
Obviously, when one of these view objects is changed, you want to update the others. However, updating the entire view is obviously inefficient.
method onSomethingHappened(uiObject)
model.appropriateAttribute = uiObject.value
The question is, what is your opinion on what to do next? Should the model object implement a callback that notifies a listener when the value has been changed, allowing one to write glue code like:
method modelChangedCallback(model, attribute)
uiObject1.value = model.a
uiObject2.value = model.a
Where you might examine what the attribute that changed is, and respond accordingly? This is the model in Objective-C and Cocoa on Mac, for the most part.
OR, would you rather have the responsibility lie completely in the glue code?
method onSomethingHappened(uiObject)
model.appropriateAttribute = uiObject.value
self.updateForAttribute("appropriateAttribute")
Both of these approaches can get pretty hairy (as is the problem with glue code) when your project gets large. Maybe there are other approaches. What do you think?
Thanks for any input!
For me I think it comes down to where the behavior is needed. In the situation you describe, the fact that you are binding multiple controls to a property is what is driving the requirement, so it doesn't make sense to add code to the model to support that.
In a web-based model I would probably put the logic in the web page since that can be done rather cheaply using Javascript. If I don't have that luxury (i.e. I'm dealing with a "dumb" view), then it would probably make sense to do it in the controller, or model glue code. If this sort of thing becomes common enough, I may go as far as creating some form of generic helper to reduce the amount of boiler-plate code I have to deal with.
In Windows Phone a ListBox support the virtualization of the data, that means it can only load the data needed and not everything. Peter Torr explains the interface you need to implement.
The short version is that you have to create both a method that return the position of an element and another one that return the element in a specific position. The problem is that the example of Peter Torr is rather dumb, he just return an object with the index as a name.
My question is: how do you actually implement this ?
My idea is to create one file that contains a list of an (integer) index and an (integer) id and a file for every object that contains the actual data. It doesn't seem a really elegant idea, but I can't think of anything better, can you ?
UPDATE
It seems that my question is inaccurate. When I say that the example of Peter Torr is "rather dumb" I am not saying that he has done anything wrong; his objective was simply to explain what interface you need to implement. The practical implementation will depend on the specific data.
What I am asking is what choices do I have to implement this ? Should I simply put the data on a web service and query it every time (with a local cache, of course), build a database, create a file the store the indexes and one for the data ? Is there a solution good enough in every case ? What are the downsides and upsides of every choice ?
The article you linked to includes a link to a downloadable project which demonstrates how to implement this.
What more are you after? The general idea is that the ListBox will call into your IList when it needs data. it will ask for an item at a specific index and you pass back an object. it then, presumably, calls ToString() on that object and displays the result in the list.
What that actual object is and where you pull it from is completely up to you. You might be using a really large array in memory. You might be pulling from IsolatedStorage or a web service. You could certainly use it to pull file info, but I don't suspect anyone has a ready-built IList implementation so that's the part that you will have to implement based on your specific project.
I am writing a GUI based application where I read a string of values from serial port every few seconds and I need to display most of the values in some type graphical indicator(I was thinking of QprogressBar maybe) that displays the range and the value. Some of the other data that I am parsing from the string are the date and fault codes. Also, the data is hierarchical.
I wanted to use the model/view architecture of Qt because I have been interested in MVC stuff for a while but have never quite wrapped my brain around how to implement it very well.
As of now, I have subclassed QAbstractItemModel and in the model I read the serial port and wrap the items parsed from the string in a Tree data structure. I can view all of the data in a QtreeView with no issues.
I have also began to subclass QAbstractItemView to build my custom view with all of the Graphical Indicators and such. This is where I am getting stuck. It seems to me that in order for me to design a view that knows how to display my custom model the view needs to know exactly how all of the data in the model is organized. Doesn't that defeat the purpose of Model/View? The QTreeView I tested the model with is basically just displaying the model as it is setup in the Tree structure but I don't want to do that because the data is not all of the same type. Is the type of data or the way you would like to present it to the user a determining factor in whether or not you should use this architecture? I always assumed it was just always better to design in an MVC style.
It seems to me like it might have been better to just subclass QWidget and then read in from the serial port and update all of subwidgets(graphical indicators, labels, etc...) from the subclass. Essentially, do everything in one class.
Does anybody understand this issue that can explain to me either what I am missing or why I shouldn't be doing it this way. As of now I am a little confused.
Thanks so much for any help!
** ** - Is this a situation where Qt Model/View architecture is not useful?
I"m going to say not necessarily - end edit
I'm not sure I fully understand your question, but let me try.
First, let's talk about MVC display pattern. This pattern is all about breaking the program into separate (and hopefully testable) sections that have their own areas of concerns.
The model is data structures that describe your data. I'm sure that there is some statistical data is also present. It is important that the model not know anything about how the data is going to be displayed to the user.
The View is how information is presented to user. It is not suppose to care about how the data is presented for displaying. It is important for this layer to be unaware of how the model gets the data for display.
The control logic is the "glue" to connects the first two items together. This is the layer that holds all the "messy" stuff to make to good user experience. EDIT - Most of what QT calls a "view item" I would probably put in the controller layer.
But if you do this, then the model and controller layers become very testable.
With that being said, many of your points are not really related to MVC pattern. You seem to be discussing what is the optimum way to display the data. This is always a problem. And without seeing your app, I'm not really going to try to tell you what is going to look good.
But by following good MVC pattern design, you can make pretty significant revision to the display without effecting the underling code.
This being said, I'm dealing with this exact issue right now and this pattern is working well form me. If you go to codeplex.com and search for mvvm (model-view-viewmodel, term used in WPF), you will see a number of projects that use it that you can use to get more information.
If this is not enough, let me know and I may be able to give you a better answer.