I'm following this tutorial about Ionic and directives and everything works fine except when I try to get the FAB element using ElementRef's nativeElement.getElementsByClassName, like this:
this.fab = this.element.nativeElement.getElementsByClassName('fab')[0]
That returns undefined. The problem is when I remove the index and print the whole HTMLCollection using console.log, it shows me a complete list with all the FAB's inside the element.
Running
console.log(this.element.nativeElement.getElementsByClassName('fab'),
this.element.nativeElement.getElementsByClassName('fab')[0]);
on ngOnInit gives the following result:
What am I doing wrong here? Every part of the code related to the problem is equal to the tutorial and it's a quite recent video...
I think the reason here is that those elements are not present while you asking for them with that line:
console.log(this.element.nativeElement.getElementsByClassName('fab'),
this.element.nativeElement.getElementsByClassName('fab')[0]);
There is simple example which shows where problem can be:
console.log(document.getElementsByClassName('fab'), document.getElementsByClassName('fab')[0]);
const el1 = document.createElement('div');
el1.setAttribute('class', 'fab');
const el2 = document.createElement('div');
el2.setAttribute('class', 'fab');
setTimeout(() => {
this.abc.nativeElement.appendChild(el1);
this.abc.nativeElement.appendChild(el2);
}, 2000);
Elements are added after 2 seconds and console log is same like yours, but when you click on HTMLCollection it will evaluate and shows you those elements - of course if you click after 2 seconds(when elements are present).
If those element are really present when you asking for them console log should look more like:
HTMLCollection(2) [div.fab, div.fab]
Also, note that this little i in Google Chrome console inform you that value is evaluted just now - at the moment when you click on it.
In Polymer 1.x I was used to write a templatize code like this:
renderTemplate(query, properties) {
let element = this.shadowRoot.querySelector(query);
this.templatize(element);
var instance = this.stamp(properties);
return instance;
}
which worked well. But in Polymer 2.x there is a new error message A <template> can only be templatized once. Well it doesn't make sense, because I have 1 template which I want to redistribute multiple times with different properties.
I am giving here an example of how is my code
I have #template1 and #template2
I want to render #template1 then #template2 then #template1.
In steps how I render templates:
1) templatize #template1
2) stamp properties
3) templatize #template2
4) stamp properties
5 a) templatize #template1 => ERROR
5 b) skip templatize and stamp properties => #template2 is rendered....
How am i able to make this possible? calling stamp() after rendering #template2 will result in another #template2 render. I want #template1, but I can't templatize #template1 because it has been already templatized. And stamp is always "binded" to last templatized element.
Am I doing something wrong? I do really hate Polymer because of it's bad documentation and hard to google something usefull
I found a workaround which is propably not the best solution but it works. I tried to search in source code for some solutions but there wasn't anything usefull except the one property called __templatizeOwner. This property is set to all templatized elements. Removing this property from an element is the way.
renderTemplate(query, properties) {
let element = this.shadowRoot.querySelector(query);
if(element.__templatizeOwner) {
element.__templatizeOwner = null;
}
this.templatize(element);
var instance = this.stamp(properties);
return instance;
}
I am not sure what side effects this might have (more memory usage or something) but this is the only way I was able to find out.
I know the attached function doesn't guarantee that properties will be loaded.
Right now, I've been using a computed Function that depends on properties but it's very clunky.
I've also used async but I find it to be inconsistent and arbitrary (just picking a random time to delay by).
I can't find anything about the correct way to deal with this problem.
You can use observers.
for example you
properties:{
someproperty:{type:Number,observer:'change'}
},
change:function(){
//this function called when the property changes.
}
for more information look at https://www.polymer-project.org/1.0/docs/devguide/properties.html
In addition to Alon's answer: if you want to observe several properties, then you can use something like this:
properties:{
someproperty1:{
type: Number,
}
someProperty2:{
type: Number,
}
},
observers: ['change(someproperty1, someproperty2)'],
change:function(property1, property2){
//this function called when the property changes.
},
Note, when using single observers, they will fire in the order they are set. So if someproperty1 and someproperty2 had specific observers binded to them, then the method that someproperty1 had will be executed first.
To read more about observers, read here:
https://www.polymer-project.org/1.0/docs/devguide/observers#multi-property-observers
There are many examples of doing this in axml, but I would like to have a complete binding using code behind. To be honest, I would like to have NO axml, but seems like creating all the controls programmatically is a nightmare.
I first tried the suggestions at:
MvxListView create binding for template layout from code
I have my list binding from code-behind, and I get six rows (so source binding is working); but the cells itself does not bind.
Then at the following url:
Odd issue with MvvmCross, MvxListViewItem on Android
Stuart has the following comment: Have looked through. In this case, I don't think you want to use DelayBind. DelayBind is used to delay the binding action until next time the DataContext is set. In Android's MvxAdapter/MvxListItemView case, the DataContext is passed in the ctor - so DataContext isn't set again until the cell is reused. (This is different to iOS MvxTableDataSource).
So in essence, the only example I see shows DelayBind, which shouldn't work.
Can someone please show me some examples... thanks in advance.
Added reply to Comments:
Cheesebaron, first of all, a huge thank you and respect for all your contributions;
Now, why not use axml? Well, as programmers, we all have our own preferences and way of doing stuff - I guess I am old school where we didn't have any gui designer (not really true).
Real reasons:
Common Style: I have a setup where Core has all the style details, including what all the colors would be. My idea is, each platform would get the style details from core and update accordingly. It's easy for me to create controls with the correct style this way.
Copy-Paste across platform (which then I can even have as linked files if I wanted). For example, I have a login screen with web-like verification, where a red error text appears under a control; overall on that screen I have around 10 items that needs binding. I have already got iOS version working - so starting on Droid, I copied the whole binding section from ios, and it worked perfectly. So, the whole binding, I can make it same across all platform... Any possible error in my way will stop at building, which I think is a major advantage over axml binding. Even the control creation is extremely similar, where I have helpers with same method name.
Ofcourse I understand all the additional layout that has to be handled; to be honest, it's not that bad if one really think it through; I have created a StackPanel for Droid which is based on WP - that internally handles all the layouts for child views; so for LinearLayout, all I do is setup some custom parameters, and let my panel deal with it. Relative is a different story; so far, I have only one screen that's relative, and I can even make it Linear to reduce my additional layout code.
So, from my humble point of view, for my style, code-behind creation allows me to completely copy all my bindings (I do have some custom binding factories to allow that), copy all my control create lines; then only adding those controls to the view is the only part that is different (then again, droid and WP are almost identical). So there is no way I can miss something on one platform and all are forced to be the same. It also allows me to change all the styles for every platform just by changing the core. Finally, any binding error is detected during compile - and I love that.
My original question wasn't about NOT using axml... it was on how to use MvxListView where all the binding is done in code-behind; as I have explained, I got the list binding, but not the item/cell binding working.
Thanks again in advance.
Here is part of my LoginScreen from droid; I think it's acceptable amount of code for being without axml file.
//======================================================================================================
// create and add all controls
//======================================================================================================
var usernameEntry = ControlHelper.GetUITextFieldCustom(this, "Username.", maxLength: 20);
var usernameError = AddErrorLabel<UserAuthorization, string>(vm => ViewModel.Authorization.Username);
var passwordEntry = ControlHelper.GetUITextFieldCustom(this, "Password.", maxLength: 40, secureTextEntry: true);
var passwordError = AddErrorLabel<UserAuthorization, string>(vm => ViewModel.Authorization.Password);
var loginButton = ControlHelper.GetUIButtonMain(this);
var rememberMe = new UISwitch(this);
var joinLink = ControlHelper.GetUIButtonHyperLink(this, textAlignment: UITextAlignment.Center);
var copyRightText = ControlHelper.GetUILabel(this, textAlignment: UITextAlignment.Center);
var copyRightSite = ControlHelper.GetUIButtonHyperLink(this, textAlignment: UITextAlignment.Center);
var layout = new StackPanel(this, Orientation.Vertical)
{
Spacing = 15,
SubViews = new View[]
{
ControlHelper.GetUIImageView(this, Resource.Drawable.logo),
usernameEntry,
usernameError,
passwordEntry,
passwordError,
loginButton,
rememberMe,
joinLink,
ControlHelper.GetSpacer(this, ViewGroup.LayoutParams.MatchParent, weight: 2),
copyRightText,
copyRightSite
}
};
I just came across a similar situation myself using Mvx4.
The first link you mentioned had it almost correct AND when you combine it from Staurts comment in the second link and just remove the surrounding DelayBind call, everything should work out ok -
public class CustomListItemView
: MvxListItemView
{
public MvxListItemView(Context context,
IMvxLayoutInflater layoutInflater,
object dataContext,
int templateId)
: base(context, layoutInflater, dataContext, templateId)
{
var control = this.FindViewById<TextView>(Resource.Id.list_complex_title);
var set = this.CreateBindingSet<CustomListViewItem, YourThing>();
set.Bind(control).To(vm => vm.Title);
set.Apply();
}
}
p.s. I have asked for an Edit to the original link to help others.
I try to make a photo-app that can read Qr-Codes with the ZXing-Library.
Most parts work but now somehow my LowLagPhotoCapture doesn't return anything useful:
var photoProperties = MediaProperties.ImageEncodingProperties.createJpeg();
mediaCaptureMgr.prepareLowLagPhotoCaptureAsync(photoProperties)
.done(function (_lowLagPhotoCapture) {
lowLagPhotoCapture = _lowLagPhotoCapture;
lowLagPhotoCapture.captureAsync()
.done(function (capturedPhoto) {
...
The MediaCaptureMgr works, I see a preview of the cam on the screen. But now I need to make a photo. The usual PhotoCapture didn't work with JavaScript and so I found this solution.
Somehow the lowLagPhotoCapture.captureAsync() crashes saying that lowLagPhotoCapture is empty. lowLagPhotoCapture is defined outside of this class because I need it later. But even if I pass the variable directly to the new method it fails =/
Any ideas what might go wrong with this?
Edit:
Okay, after every Async-operation I had a following nameless function and one exitOnError-function that was calles every time. If I remove thatv exitOnError-function out of .done(complete, error), it exits in the same place. But if I set a breakpoint on .captureAsync it goes 1-2 steps further, creates an ImageStream and exits somewhere there. Why the different behaviour with and without the breakpoint?