I am getting always nil ITLibMediaItem.location attribute.
// let library: ITLibrary = try ITLibrary(APIVersion: "1.0")
// library.reloadData()
if let mediaItem = iTuneMediaItem {
if let location = mediaItem.location{
return location.path
}else{
print("nil location")
}
}else{
print("nil mediaItem")
}
If i enable commented line to reload library before get location it is working, but i don't want to reload library every time because it takes time if we have large iTunes playlist.
can please anyone explain how we can fix without reloading library every time?
EDIT :
I am using ITLibMediaItem from ITLibPlaylist.items[]
I figure the fix is need to make static app level attribute of ITLibrary and reload once at init.
Related
This might not be the question but it was the list of doubts which comes when learning native script from scratch.
I had a 1000 or more list of data stored in data table. know i want to display it on a list view but i don't want to read all the data at once. because i have images stored in other directory and want to read that also. So, for 20 to 30 data's the performance is quite good. but for 1000 data it is taking more than 15 minutes to read the data as well as images associated with it. since i'm storing some high quality images.
Therefore i decided to read only 20 data's with their respective images. and display it on list. know when user reaches the 15th data of the list. i decided to read 10 more data from the server.
know when i search this i came across "RadListView Load on Demand".
then i just looked at the code below.
public addMoreItemsFromSource(chunkSize: number) {
let newItems = this._sourceDataItems.splice(0, chunkSize);
this.dataItems.push(newItems);
}
public onLoadMoreItemsRequested(args: LoadOnDemandListViewEventData) {
const that = new WeakRef(this);
const listView: RadListView = args.object;
if (this._sourceDataItems.length > 0) {
setTimeout(function () {
that.get().addMoreItemsFromSource(2);
listView.notifyLoadOnDemandFinished();
}, 1500);
args.returnValue = true;
} else {
args.returnValue = false;
listView.notifyLoadOnDemandFinished(true);
}
}
In nativescript if i want to access binding element xml element. i must use observables in viewmodel or exports.com_name on associated js file.
but in this example it is started with public..! how to use this in javascript.
what is new WeakRef(this) ?
why it is needed ?
how to identify user has scrolled to 15 data, as i want to load more data when he came at 15th data.
after getting data how to update array of list and show it in listview ?
Finally i just want to know how to use load on demand
i tried to create a playground sample of what i have tried but it is giving error. it cannot found module of radlistview.
Remember i'm a fresher So, kindly keep this in mind when answering. thank you,
please modify the question if you feel it is not upto standards.
you can check the updated answer here
https://play.nativescript.org/?template=play-js&id=1Xireo
TypeScript to JavaScript
You may use any TypeScript compiler to convert the source code to JavaScript. There are even online compilers like the official TypeScript Playground for instance.
In my opinion, it's hard to expect ES5 examples any more. ES6-9 introduced a lot of new features that makes JavaScript development much more easier and TypeScript takes JavaScript to next level, interpreter to compiler.
To answer your question, you will use the prototype chain to define methods on your class in ES5.
YourClass.prototype.addMoreItemsFromSource = function (chunkSize) {
var newItems = this._sourceDataItems.splice(0, chunkSize);
this.dataItems.push(newItems);
};
YourClass.prototype.onLoadMoreItemsRequested = (args) {
var that = new WeakRef(this);
var listView = args.object;
if (this._sourceDataItems.length > 0) {
setTimeout(function () {
that.get().addMoreItemsFromSource(2);
listView.notifyLoadOnDemandFinished();
}, 1500);
args.returnValue = true;
} else {
args.returnValue = false;
listView.notifyLoadOnDemandFinished(true);
}
}
If you are using fromObject syntax for your Observable, then these functions can be passed inside
addMoreItemsFromSource: function (chunkSize) {
....
};
WeakRef: It helps managing your memory effiencetly by keeping a loose reference to the target, read more on docs.
How to load more:
If you set loadOnDemandMode to Auto then loadMoreDataRequested event will be triggered whenever user reaches the end of scrolling.
loadOnDemandBufferSize decides how many items before the end of scroll the event should be triggered.
Read more on docs.
How to update the array:
That's exactly what showcased in addMoreItemsFromSource function. Use .push(item) on the ObservableArray that is linked to your list view.
I am facing the following problem,
I have an object called "data". It has three properties, one of it being itemRendererData. The "itemRendererData" is an ArrayCollection of objects having many properties one of which is the property "imageURL" (datatype:String).
I am working in flex. I have defined the view and the item renderer properly. The view has the data. I am supposed to get the images from the url specified by imageURL property.
In the itemRenderer, I have declared, source
source = {data.itemRendererData.imageURL}
But the images are not being displayed.
Use a the FlexEvent.DATA_CHANGE handler rather than binding, which is actually the proper way to handle this and gives you far more control.
public function CustomItemRenderer() {
this.addEventListener(FlexEvent.DATA_CHANGE, this.dataChangeHandler);
this.addEventListener(FlexEvent.CREATION_COMPLETE, this.creationCompleteHandler);
}
private function creationCompleteHandler(e:FlexEvent) {
if (this.data) {
this.image.source = this.data.itemRendererData.imageURL;
}
}
private function dataChangeHandler(e:FlexEvent) {
if (this.data && this.initialized) {
this.image.source = this.data.itemRendererData.imageURL;
}
}
You will notice that I have a handler for FlexEvent.CREATION_COMPLETE as well. This is because the data is actually set before the components are created. So the first time a renderer is loaded, this.image is null and this.image.source will error out.
If that doesn't work, you also need to make sure that the Image/BitmapImage is not a direct child of the renderer. I never did figure out why this was, but adding it as a child of Group fixed that issue where the image was being set but not rendering. Again, I have no idea why this was and I tested for a few hours trying to figure it out.
As an added tip, avoid MXML-based ItemRenderers in mobile applications. They are noticeably slower than pure-AS3 renderers.
Im working on a MVVM Windows phone app that displays weather info.
When the app loads up it opens MainPage.xaml. It makes a call the the service to get weather info and binds that data to the UI. Both Fahrenheit and Celcius info are returned but only one is displayed.
On the setting page, the user can select to view the temp in either Fahrenheit or Celcius.
The user can change this setting at any time and its stored in IsolatedStorageSettings.
The issue Im having is this:
when the user navigates to the Settings page and changes their preference for either Fahrenheit or Celcius, this change is not reflected on the main page.
This issue started me thinking about this in a broader context. I can see this being an issue in ANY MVVM app where the display depends on some setting in IsolatedStorage. Any time any setting in the IsoStore is updated, how does the ViewModels know this? When I navigate back in the NavigationStack from the settings page back to MainPage how can I force a rebind of the page?
The data in my model hasnt changed, only the data that I want to display has changed.
Am I missing something simple here?
Thanks in advance.
Alex
Probably you have code like this:
public double DisplayTemperature
{
get { return (IsCelsium) ? Celsium : Fahrenheit; }
}
And IsCelsium is:
public double IsCelsium
{
get { return (bool)settings["IsCelsium"]; }
set { settings["IsCelsium"] = value; }
}
So you need to add NotifyPropertyChanged event to notify UI to get new values from DisplayTemperature property:
public double IsCelsium
{
get { return (bool)settings["IsCelsium"]; }
set
{
settings["IsCelsium"] = value;
NotifyPropertyChanged("DisplayTemperature");
}
}
Take a look at Caliburn Micro. You could implement something similar or use CM itself. When using CM I don't even think about this stuff, CM makes it so simple.
When your ViewModel inherits from Screen there are life-cycle events that fire that you can override. For example, OnInitialize fires the very first time the ViewModel is Activated and OnActivate fires every time the VM is activated. There's also OnViewAttached and OnViewLoaded.
These methods are the perfect place to put logic to populate or re-populate data.
CM also has some special built in features for allowing one to easily tombstone a single property or an entire object graph into Iso or phone state.
ok, so Ive come up with a solution. Before I get to it, let me provide some background. The app that Im working on uses both MVVM Light and WP7Contrib. That being the case, I am using Funq for DI and the MVVMLight Toolkit. After I posted my initial question, I gave the question a bit more thought. I remembered a video that I watched a while back from MIX2011 called Deep Dive MVVM with Laurent Bugnion
http://channel9.msdn.com/Events/MIX/MIX11/OPN03
In it, he talks about just this problem (view models not living at the same time) on Windows Phone. The part in question starts around the 19 minute mark.
Anyway, after I remembered that and realized that the ViewModel locator is exposed in App.xaml, this became a trivial problem to solve. When the user changes the Fahrenheit/Celcius option on the setting page, I simply get a reference to the MainViewModel via the ViewModelLocator and reset the collection that is bound to the UI thus causing the bindings to update.
public bool AddOrUpdateValue(string Key, Object value)
{
bool valueChanged = false;
// If the key exists
if (settings.Contains(Key))
{
// If the value has changed
if (settings[Key] != value)
{
// Store the new value
settings[Key] = value;
valueChanged = true;
}
}
// Otherwise create the key.
else
{
settings.Add(Key, value);
valueChanged = true;
}
return valueChanged;
}
public bool ImperialSetting
{
get
{
return GetValueOrDefault<bool>(ImperialSettingKeyName, ImperialSettingDefault);
}
set
{
if (AddOrUpdateValue(ImperialSettingKeyName, value))
{
Save();
RaisePropertyChanged("ImperialSettingText");
var vml = new ViewModelLocator();
vml.MainViewModel.Cities = (App.Current as App).Cities;
}
}
}
It was a mistake on my part not to realize that I could get access to the viewModel via the ViewModelLocator. Hopefully this post saves someone else the time I burned on this issue.
I try to reload a Web page using (JavaXPCOM):
nsIWebBrowser webBrowser = (nsIWebBrowser) browser
.getWebBrowser();
nsIWebNavigation webNavigation = (nsIWebNavigation) webBrowser.queryInterface(nsIWebNavigation.NS_IWEBNAVIGATION_IID);
try {
nsISHistory sessionHistory = webNavigation.getSessionHistory();
if (sessionHistory != null) {
webNavigation = (nsIWebNavigation) sessionHistory.queryInterface(nsIWebNavigation.NS_IWEBNAVIGATION_IID);
}
} catch (XPCOMException e) {
}
webNavigation.reload(nsIWebNavigation.LOAD_FLAGS_NONE);
But reload doesn't happen at all. I tried force it by using the following flags, but page doesn't refresh as well:
nsIWebNavigation.LOAD_FLAGS_BYPASS_PROXY|nsIWebNavigation.LOAD_FLAGS_BYPASS_CACHE
Anyone knows what can be the reason for that?
Thanks!
Did you try checking Error Console for syntax errors? You seem to be trying to use C++ type casts in JavaScript. That cannot work. Assuming that browser is a <browser> element, this should work:
browser.reload();
Or:
browser.reloadWithFlags(Components.interfaces.nsIWebNavigation.LOAD_FLAGS_BYPASS_PROXY|Components.interfaces.nsIWebNavigation.LOAD_FLAGS_BYPASS_CACHE);
See https://developer.mozilla.org/en/XUL/browser for documentation on the <browser> element.
Edit: Given that this is apparently using JavaXPCOM the code seems to be correct with the exception that the entire try .. catch block should be removed. The only flag should be LOAD_FLAGS_BYPASS_CACHE to make sure you don't get a cached response.
I'm writing a Dashboard widget in Dashcode, and I'd like to add some sort of check-for-updates functionality. I already looked into Sparkle, but AFAICT it's not applicable to widgets like this. Is there a commonly-used library to do update checking, or will I have to develop my own system?
I only need a very simple setup... automatically checking for new versions would be a plus, but if the user had to click a button in order to check that would be OK with me.
Inasmuch as "is there a function that will..." then i have not come across it.
What i did was as follows
In the plist there is the version of the widget and you put the number in there, lets say 1.0. Which you should be able to access and use. (see code) For reason i didn't and added this global var widget_version = "1.4"; and then updated that when the widget updated.
Then on a server accessible by the web you create a php (or whatever) file that has the number of current version of the widget. Again lets say 1.1.
Then you write a javascript function than will check this current widget version against the server version and display a graphic or message to tell the user. It is best to let the user decide if they want to upgrade rather than making it automatic.
Following is the code i used. Please copy and or hack as you wish.
function getSoftwareUpdate() {
// so use the built in CURL to do a REST call n.b. in widget preference you will need to check 'allow network access'
var softwareUpdate = widget.system("/usr/bin/curl 'http://api.yourserver.com/widget/wfccupdate.php'", null).outputString;
//alert(softwareUpdate); // tells you the function has been called
//alert("the update number from the REST " + softwareUpdate); // for debugging will show the key
// in main.js add this line
// var widget_version = "1.4"; // this is changed when you update the widget code for new release
// yes it's a global variable and bad but i was in a hurry
// the following line should get the widget number but for some reason i didn't do it
// localVersion = widget.preferenceForKey(preferenceForKey);
//alert("the internal preference key " + widget_version);
// then check to see if they match
if(softwareUpdate == widget_version)
{ hide_update('softwareupdate')
}
else
{show_update('softwareupdate')
}
}
function hide_update(el) { // hide the update graphic
if(document.getElementById(el))
{
if(document.getElementById(el).style.display != "none")
document.getElementById(el).style.display = "none";
}
}
function show_update(el) { // show the update graphic
if(document.getElementById(el)) {
if(document.getElementById(el).style.display == "none")
document.getElementById(el).style.display = "block";
}
}
// this is the php that is called by curl and acts as REST
<?php
// data
$UPDATE_database = <<<_UPDATE_
<?xml version="1.0" encoding="utf-8" ?>
<update>
<widgetversion>1.1</widgetversion>
</update>
_UPDATE_;
// load data
$xml = simplexml_load_string($UPDATE_database);
$result = $xml->xpath("widgetversion");
print $result[0];
?>
Hope this helps