ChangeDetection | Automatically track websites changes on Android | Android library
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Trending Discussions on ChangeDetection
QUESTION
I have an angular code which is running fine, but I still do not have a concrete understanding of how change detection works.
The following component displays a table using material design and implements table pagination. I did the following steps:
- Set changeDetection to OnPush mode.
- Obtained a reference of the paginator from the template using @ViewChild(MatPaginator).
- Assigned the paginator to MatTableDataSource inside ngAfterViewInit using setTimeout after 3 seconds.
The result after initial page load is that the table paginator works fine after 3 seconds and the page is re-rendered correctly.
And this contradicts the fact that in OnPush mode, setTimeout should not trigger change detection and I am not changing the reference of any input property. Any thoughts?
...ANSWER
Answered 2022-Apr-08 at 08:05There's a few other causes for change detection with the OnPush
strategy, it is probably the MatTable
component that is triggering change detection on itself when the paginator
is changed.
A quote taken from here:
https://blog.angular-university.io/how-does-angular-2-change-detection-really-work/
When using OnPush detectors, then the framework will check an OnPush component when any of its input properties changes, when it fires an event, or when an Observable fires an event
You would have to look at the source code of the mat table to find the exact cause, but as you can see it's difficult to control change detection of a pre-made component.
Every component has its own change detector, setting the parent to OnPush
will stop most change detections from permeating down to that child, but it will not stop the child triggering change detection on itself.
In the source code we see this note:
https://github.com/angular/components/blob/master/src/material/table/table.ts
QUESTION
There is a parent component with default changeDetection
and two child components with onPush
change detection strategy. While the input variable is being updated, the template will not update. I can't used async pipes in the ChildBComponent
as it is a global UI component for the project and refactoring is not an option. How do I go about this?
parent.ts
...ANSWER
Answered 2022-Feb-08 at 17:31The problem is not with Change Detection, and the label values are correctly reflected in html. The change in countA
and countB
values do get reflected in HTML, it's just the CSS that gives the impression as if the html is not updated.
In fieldtabs.component.html
you have logic to display tabs via
- and you also have
.
The problem is when the device has max width of 767.98px
, the
- element is not shown as a result of below CSS:
QUESTION
I use this component code:
HTML:
...ANSWER
Answered 2022-Feb-08 at 14:52I think the problem is backwards from what you think it is. Jasmine assertions give the "found" value first and the expected value second. It's expecting ''
but finding 'First post title'
.
I think. Jasmine assertion responses always get me mixed up ^^
QUESTION
I have started Android development and this is my first stackoverflow question. I have tried deleting as well as making a new fileHash file. I have aslo tried deleting .gradle file. I am not able to understand, can you guys please help?
...ANSWER
Answered 2021-Aug-13 at 11:33You shouldn’t delete gradle files. Why did you delete those files? However At this point I’d delete the whole project and recreate a new one copy/pasting your code.
QUESTION
We use many Angular material fields and they are all presented the same. I want a way to simplify any changes coming from UI designers and maintenance later.
How can I create a component that reduces this block of HTML (just example code)
...ANSWER
Answered 2022-Feb-02 at 05:09The reason you are seeing the The app cannot find my 'form'
error is because you are using the formControlName
directive inside the component that is supposed to be implementing the formControlName
interface. If you remove the formControlName
directive from your custom input component template, you will no longer see that error.
In other words, when implementing ControlValueAccessor
you are essentially telling Angular that your component knows how to use the formControlName
directive and so the formControlName
directive should be put on your custom component when instantiating it. i.e.
QUESTION
I'm trying to create a custom checkbox component to replace an old-old NG Prime version that had been being used but wanted to make it leaner/cleaner with some added aria points and utilizing more of the checkbox attributes directly. The problem I'm running into though (I'm guessing) is with updating the value accessor / ngmodel and could use some guidance on what I'm apparently missing...
I thought what I had was simplistic enough but apparently not. The idea is that @Input() binary
is set to true
by default expecting ngModel
to have a boolean to use but I don't get the value from ngModel
when it's initialized. I need ngModel
to communicate that to the component though when it's used standalone as like but also have
value_accessor
working as expected if it's used in say a reactive angular form etc.
I also get a "NG0303: Can't bind to 'checked' since it isn't a known property of 'app-checkbox'" in my instance, but it's not on the stackblitz which I don't understand.
👉 A Stackblitz showing the implementation / problem
(the example is angular 12, I use 13, but it's fine for the example)
And for quick code reference;
.ts
...ANSWER
Answered 2022-Jan-22 at 00:18this would work and also you can simplify your updateModel
function. logic is a bit complicated.
model
was change after component loads, you just need to catch it and set the value of the isChecked to what is the value provided outside the component.
QUESTION
My app contains the following modules where I've the same component (AppComponent) as bootstrap.
app.module.ts
...ANSWER
Answered 2022-Jan-12 at 09:41Pretty sure that note the clear way to do it but I found a solution. I now have two bootstrap controllers (AppController and AppNewController) and on the others controller
QUESTION
Background Info
I need to modify an existing drop down component that is populated from a database, to add an "All locations" option. We do not want to add this to the db, but just include in the list of options - as the first item.
I am not an angular developer and so I'm a little lost on how to accomplish this:
Code
From what I can tell, the drop down is created from logic inside a location-options.component.ts file:
...ANSWER
Answered 2021-Dec-21 at 18:40Several ways you can do it.
Simple solution would be :
Write an option tag wth default value just before the option tag doing ngFor.
QUESTION
I'm using an angular full calendar in my project and I have tried this https://mattlewis92.github.io/angular-calendar/#/kitchen-sink.
but in this, I'm getting some errors.
here is my HTML code
...ANSWER
Answered 2021-Dec-13 at 10:40The errors regarding event.color.primary
should be the result, that your colors are of type any
and there is no specific type defined.
Try to create a IColors
interface and define the primary
and secondary
entries as string.
The errors regarding the input
tag, result from not known attributes of the input HTML element to angular.
QUESTION
I'm using eclipse Version: 2021-09 (4.21.0)
This is my gradle version
...ANSWER
Answered 2021-Nov-09 at 07:40Here is what you can do , First of all you can make sure that you have the environment variable needed , GRADLE_USER_HOME is usually located at Users/%USERNAME%/.gradle
.
Then you can make sure that you add the /gradle_installation_Foler/bin
to path .
Then try to go with gradle build , using command link at the location of your build.gradle
, this will definitely make sure if you are able to download the dependency and have no issue with access .
if you do have connection issue , and you need to use a VPN here is an old answer of mine for how to do that .
let me know in comments if new error occurred .
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