How to create dismissable Clarity labels? - label

In the Clarity Components documentation there is a working example for "Dimissing labels", but unfortunately there is no example code for this case.
See https://v2.clarity.design/labels
The documentation says - A label can be dismissed. Use a close icon at the right-most side of a label to dismiss it.
How do I create the label in the example?
I tried the following without success (just hoping for the best)
<span class="label" >james#test.com<clr-icon shape="close" ></clr-icon></span>

There is not an implementation of this behavior, rather it is just a CSS/HTML example that shows what the pattern would look like. It is up to the application to handle the 'dismissing' of the label by removing the label on click of the close button.

You can write a directive, say dismissable and have it add a X icon to labels, and which could emit an event whenever user clicks the X.
import { Directive, ElementRef, Renderer2, AfterViewInit, Output, EventEmitter } from '#angular/core';
#Directive({
selector: '[dismissable]'
})
export class DismissabelDirective implements AfterViewInit {
#Output()
close = new EventEmitter();
constructor(private renderer: Renderer2, private elRef: ElementRef) {
}
ngAfterViewInit() {
let icon = this.renderer.createElement('clr-icon');
icon.setAttribute('shape', 'close');
icon.style.margin = '1rem;'
this.renderer.setStyle(icon, 'margin-left', '0.5rem');
this.renderer.setStyle(icon, 'margin-right', '-0.25rem');
this.renderer.setStyle(icon, 'cursor', 'pointer');
this.renderer.appendChild(this.elRef.nativeElement, icon);
this.renderer.listen(icon, 'click', () => {this.close.emit(); return true;})
}
}
You could use it like below:
app.component.html
<div class="container">
<span class="label" dismissable (close)="delete(item)" *ngFor="let item of items">{{item}}</span>
</div>
app.component.ts
import { Component } from '#angular/core';
#Component({
selector: 'my-app',
templateUrl: './app.component.html',
styleUrls: [ './app.component.css' ]
})
export class AppComponent {
items = ['Apple', 'Orange', 'Banana'];
delete(item) {
const index: number = this.items.indexOf(item);
if (index !== -1) {
this.items.splice(index, 1);
}
}
}
Here is complete StackBlitz: https://stackblitz.com/edit/clarity-light-theme-v2-dismissable-labels

Related

Nativescript 6.0 How to get the focuschangeListener for Searchbar in Android

I implement the project in Nativescript angular. In nativescript 5.0 I was get the focus change listener using the following code. After updating 6.0 I face the issue in android.
Reason: The Search bar extends the androidx widget anyone help how to fix the issue in 6.0.
<SearchBar id="searchBarMall"
[hint]="searchMall" (loaded)="searchBarloaded($event)"
(textChange)="onTextChanged($event)" (clear)="onClear($event)"
(submit)="onSubmit($event)"
textFieldHintColor="gray"></SearchBar>
Typescript
import { SearchBar } from "tns-core-modules/ui/search-bar";
import { Component, OnInit } from "#angular/core";
import { Page, isAndroid } from "tns-core-modules/ui/page";
#Component({
selector: "Home",
moduleId: module.id,
templateUrl: "./home.component.html",
styleUrls: ["./home.component.css"]
})
export class HomeComponent implements OnInit {
searchPhrase: string;
private searchbar: any;
onSearchSubmit(args): void {
let searchBar = <SearchBar>args.object;
console.log("You are searching for " + searchBar.text);
}
constructor(private _page: Page) {
}
ngOnInit(): void {
}
searchBarloaded(args) {
if (isAndroid) {
let self = this;
let searchBar = <SearchBar>args.object;
searchBar.android.setOnQueryTextFocusChangeListener(new android.view.View.OnFocusChangeListener({
onFocusChange: function (v: any, hasFocus: boolean) {
console.log("Focus" + hasFocus);
}
}));
this.searchbar.android.setFocusable(false);
this.searchbar.android.clearFocus();
}
}
ngAfterViewInit() {
this.searchbar = <SearchBar>this._page.getViewById("searchBarMall");
}
}
Use setOnQueryTextFocusChangeListener on nativeView.
this.searchbar.android.setOnQueryTextFocusChangeListener(new android.view.View.OnFocusChangeListener({
onFocusChange:function(v : any , hasFocus:boolean){
if(hasFocus){
...
}else{
...
}
}
}));

Nativescript TabView using to much space when adding title text

Is it possible to remove some of the padding inside a tabview item?
The TabView has a lot of empty unused space. If I could remove this then my tabs wouldn't get cutoff. This would greatly improve my app since now you have to swipe a bit to the right to see the full title of the last menu item.
The tabview is created in NS-Vue but I don't think that will matter since this is a native issue.
I'm using negative margins to remove padding from TabView items. That was the only solution I found to do this. This approach is needed only for Android, for iOS it works fine.
import { Component, OnInit, HostListener } from '#angular/core';
import { Page } from 'tns-core-modules/ui/page/page';
import { RouterExtensions } from 'nativescript-angular/router';
import { ActivatedRoute } from '#angular/router';
import { TabView } from 'tns-core-modules/ui/tab-view';
import * as platform from 'tns-core-modules/platform';
#Component({
selector: 'app-tabs',
moduleId: module.id,
templateUrl: './tabs.component.html'
})
export class TabsComponent implements OnInit {
tabView: TabView;
constructor(
private page: Page,
private router: RouterExtensions,
private route: ActivatedRoute
) { }
ngOnInit(): void {
this.tabView = this.page.getViewById('tab');
this.router.navigate([
{
outlets: {
homeTab: ['home'],
organizadorTab: ['organizador'],
favoritosTab: ['favoritos'],
categoriasTab: ['categorias'],
perfilTab: ['perfil']
}
}
], { relativeTo: this.route });
}
#HostListener('loaded')
onLoaded() {
if (platform.isAndroid) {
this.tabView.android.tabLayout.setTabTextFontSize(10);
const viewGroup = this.tabView.android.tabLayout.getChildAt(0);
for (let i = 0; i < viewGroup.getChildCount(); i++) {
const view = viewGroup.getChildAt(i);
const layoutParams = view.getLayoutParams();
layoutParams.width = 1;
layoutParams.leftMargin = -20;
layoutParams.rightMargin = -20;
layoutParams.topMargin = -20;
layoutParams.bottomMargin = -20;
view.setLayoutParams(layoutParams);
}
this.tabView.requestLayout();
}
}
}

NativeScript one-way databinding doesn't update view

This seems like a pretty simple case to me, but I'm obviously missing something. I have a Model to be bound to the View. I then load the Model with an Http call. Why doesn't the View update? I thought that was the whole point of one-way binding.
I have verified that I'm getting back the data I'm expecting from the http call.
Update
I added a button to the screen and databinding will actually update the screen with the http loaded data for both fields on button push, even though the button method only sets one of the values. So either there's a bug in NativeScript or I'm not doing something incorrectly.
Update 2 Just the act of clicking the button will trigger the binding to happen. I've modified the code to have an empty tap handler, and just clicking the button makes it bind.
typescript
import { Component, ChangeDetectionStrategy, OnInit } from "#angular/core";
import { Job } from "../../shared/customer/job";
import { Http, Headers, Response } from "#angular/http";
import { Observable } from "rxjs/Rx";
#Component({
selector: "my-app",
templateUrl: "pages/job-details/job-details.html",
changeDetection: ChangeDetectionStrategy.OnPush
})
export class JobDetailsComponent implements OnInit {
job: Job;
salesAssociateName: string = "x";
constructor(private http: Http) {
this.job = new Job();
}
ngOnInit() {
this.getJob(1234);
}
getJob(leadId: number) {
var url = "https://url-not-for-you/job?franchiseeid=48&leadid=" + leadId;
var headers = this.createRequestHeader();
this.http.get(url, { headers: headers }).map(response => response.json())
.do(data => this.setData(data[0]))
.subscribe(
() => this.success(),
(error) => this.error()
);
}
private createRequestHeader() {
let headers = new Headers();
headers.append("AuthKey","blah");
headers.append("AuthToken", "blee");
return headers;
}
setData(job) {
this.job.FullName = job["FullName"];
this.job.SalesAssociateName = job["SalesAssociateName"];
this.salesAssociateName = this.job.SalesAssociateName;
console.log("Found job for customer: " + job["FullName"]);
}
success() {
// nothing useful
}
error() {
alert("There was a problem retrieving your customer job.");
}
changeSA() {
}
}
html
<StackLayout>
<Label [text]="job.FullName"></Label>
<Label [text]="salesAssociateName"></Label>
<Button text="Push" (tap)="changeSA()"></Button>
</StackLayout>
Your code will work as expected with the default ChangeDetectionStrategy. however, you have changed the strategy to onPush
In order to make your binding work as expected in the default changeStrategy delete the following line
changeDetection: ChangeDetectionStrategy.OnPush
or change it to
changeDetection: ChangeDetectionStrategy.Default
More about the Angular-2 ChangeDetectionStrategy here and here
If you still want to use onPush instead of the default strategy then your properties should be declared as #input() and once the change is made (in your case in setData) marked with markForCheck()
The reason your binding is working when triggered from Button tap is because
application state change can be triggered by:
Events - tap, swipe,
XHR - Fetching data from a remote server
Timers - e.g. setTimeout()
For testing purposes and if someone is interested of how to implement the scenario with onPush here is a sample code:
import { Component, ChangeDetectionStrategy, ChangeDetectorRef, OnInit, NgZone, Input } from "#angular/core";
import { Http, Headers, Response } from "#angular/http";
import { Observable as RxObservable } from "rxjs/Rx";
import "rxjs/add/operator/map";
import "rxjs/add/operator/do";
#Component({
selector: "my-app",
templateUrl: "app.component.html",
changeDetection: ChangeDetectionStrategy.OnPush
})
export class AppComponent implements OnInit {
#Input() public job: any = { salesAssociateName: "default job" };
#Input() public salesAssociateName: string = "default name";
constructor(private http: Http, private change:ChangeDetectorRef) { }
ngOnInit() {
this.getJob();
}
getJob() {
var url = "http://httpbin.org/get";
var headers = this.createRequestHeader();
this.http.get(url, { headers: headers })
.map(response => response.json())
.do(data => {
this.setData();
}).subscribe(
() => this.success(),
(error) => this.error()
);
}
private createRequestHeader() {
let headers = new Headers();
return headers;
}
setData() {
this.job.salesAssociateName = "NEW job SalesAssociateName";
this.salesAssociateName = "NEW job FullName";
this.change.markForCheck();
}
success() {
alert("success");
}
error() {
alert("There was a problem retrieving your customer job.");
}
}

NativeScript handling back button event

I am trying to handle the hardware back button in a NativeScript app. I am using NativeScript version 2.3.0 with Angular.
Here is what I have in main.ts file
// this import should be first in order to load some required settings (like globals and reflect-metadata)
import { platformNativeScriptDynamic, NativeScriptModule } from "nativescript-angular/platform";
import { NgModule,Component,enableProdMode } from "#angular/core";
import { AppComponent } from "./app.component";
import { NativeScriptRouterModule } from "nativescript-angular/router";
import { routes, navigatableComponents } from "./app.routing";
import { secondComponent } from "./second.component";
import {AndroidApplication} from "application";
#Component({
selector: 'page-navigation-test',
template: `<page-router-outlet></page-router-outlet>`
})
export class PageNavigationApp {
}
#NgModule({
declarations: [AppComponent,PageNavigationApp,secondComponent
// ...navigatableComponents
],
bootstrap: [PageNavigationApp],
providers:[AndroidApplication],
imports: [NativeScriptModule,
NativeScriptRouterModule,
NativeScriptRouterModule.forRoot(routes)
],
})
class AppComponentModule {
constructor(private androidapplication:AndroidApplication){
this.androidapplication.on("activityBackPressed",()=>{
console.log("back pressed");
})
}
}
enableProdMode();
platformNativeScriptDynamic().bootstrapModule(AppComponentModule);
I am importing application with
import {AndroidApplication} from "application";
Then in the constrouctor of appComponentModule I am registering the event for activityBackPressed and just doing a console.log.
This does not work.
What am I missing here?
I'm using NativeScript with Angular as well and this seems to work quite nicely for me:
import { RouterExtensions } from "nativescript-angular";
import * as application from "tns-core-modules/application";
import { AndroidApplication, AndroidActivityBackPressedEventData } from "tns-core-modules/application";
export class HomeComponent implements OnInit {
constructor(private router: Router) {}
ngOnInit() {
if (application.android) {
application.android.on(AndroidApplication.activityBackPressedEvent, (data: AndroidActivityBackPressedEventData) => {
if (this.router.isActive("/articles", false)) {
data.cancel = true; // prevents default back button behavior
this.logout();
}
});
}
}
}
Note that hooking into the backPressedEvent is a global thingy so you'll need to check the page you're on and act accordingly, per the example above.
import { Component, OnInit } from "#angular/core";
import * as Toast from 'nativescript-toast';
import { Router } from "#angular/router";
import * as application from 'application';
#Component({
moduleId: module.id,
selector: 'app-main',
templateUrl: './main.component.html',
styleUrls: ['./main.component.css']
})
export class MainComponent {
tries: number = 0;
constructor(
private router: Router
) {
if (application.android) {
application.android.on(application.AndroidApplication.activityBackPressedEvent, (args: any) => {
if (this.router.url == '/main') {
args.cancel = (this.tries++ > 0) ? false : true;
if (args.cancel) Toast.makeText("Press again to exit", "long").show();
setTimeout(() => {
this.tries = 0;
}, 2000);
}
});
}
}
}
Normally you should have an android activity and declare the backpress function on that activity. Using AndroidApplication only is not enough. Try this code:
import {topmost} from "ui/frame";
import {AndroidApplication} from "application";
let activity = AndroidApplication.startActivity ||
AndroidApplication.foregroundActivity ||
topmost().android.currentActivity ||
topmost().android.activity;
activity.onBackPressed = function() {
// Your implementation
}
You can also take a look at this snippet for example
As far as I know, NativeScript has a built-in support for this but it's not documented at all.
Using onBackPressed callback, you can handle back button behaviour for View components (e.g. Frame, Page, BottomNavigation).
Example:
function pageLoaded(args) {
var page = args.object;
page.onBackPressed = function () {
console.log("Returning true will block back button default behaviour.");
return true;
};
page.bindingContext = homeViewModel;
}
exports.pageLoaded = pageLoaded;
What's tricky here is to find out which view handles back button press in your app. In my case, I used a TabView that contained pages but the TabView itself handled the event instead of current page.

Angular 2 Scroll to bottom (Chat style)

I have a set of single cell components within an ng-for loop.
I have everything in place but I cannot seem to figure out the proper
Currently I have
setTimeout(() => {
scrollToBottom();
});
But this doesn't work all the time as images asynchronously push the viewport down.
Whats the appropriate way to scroll to the bottom of a chat window in Angular 2?
I had the same problem, I'm using a AfterViewChecked and #ViewChild combination (Angular2 beta.3).
The Component:
import {..., AfterViewChecked, ElementRef, ViewChild, OnInit} from 'angular2/core'
#Component({
...
})
export class ChannelComponent implements OnInit, AfterViewChecked {
#ViewChild('scrollMe') private myScrollContainer: ElementRef;
ngOnInit() {
this.scrollToBottom();
}
ngAfterViewChecked() {
this.scrollToBottom();
}
scrollToBottom(): void {
try {
this.myScrollContainer.nativeElement.scrollTop = this.myScrollContainer.nativeElement.scrollHeight;
} catch(err) { }
}
}
The Template:
<div #scrollMe style="overflow: scroll; height: xyz;">
<div class="..."
*ngFor="..."
...>
</div>
</div>
Of course this is pretty basic. The AfterViewChecked triggers every time the view was checked:
Implement this interface to get notified after every check of your component's view.
If you have an input-field for sending messages for instance this event is fired after each keyup (just to give an example). But if you save whether the user scrolled manually and then skip the scrollToBottom() you should be fine.
Simplest and the best solution for this is :
Add this #scrollMe [scrollTop]="scrollMe.scrollHeight" simple thing on Template side
<div style="overflow: scroll; height: xyz;" #scrollMe [scrollTop]="scrollMe.scrollHeight">
<div class="..."
*ngFor="..."
...>
</div>
</div>
Here is the link for WORKING DEMO (With dummy chat app) AND FULL CODE
Will work with Angular2 and also upto 5, As above demo is done in
Angular5.
Note :
For error : ExpressionChangedAfterItHasBeenCheckedError
Please check your css,it's a issue of css side,not the Angular side
, One of the user #KHAN has solved that by removing overflow:auto; height: 100%; from div. (please check conversations for detail)
The accepted answer fires while scrolling through the messages, this avoids that.
You want a template like this.
<div #content>
<div #messages *ngFor="let message of messages">
{{message}}
</div>
</div>
Then you want to use a ViewChildren annotation to subscribe to new message elements being added to the page.
#ViewChildren('messages') messages: QueryList<any>;
#ViewChild('content') content: ElementRef;
ngAfterViewInit() {
this.scrollToBottom();
this.messages.changes.subscribe(this.scrollToBottom);
}
scrollToBottom = () => {
try {
this.content.nativeElement.scrollTop = this.content.nativeElement.scrollHeight;
} catch (err) {}
}
I added a check to see if the user tried to scroll up.
I'm just going to leave this here if anyone wants it :)
<div class="jumbotron">
<div class="messages-box" #scrollMe (scroll)="onScroll()">
<app-message [message]="message" [userId]="profile.userId" *ngFor="let message of messages.slice().reverse()"></app-message>
</div>
<textarea [(ngModel)]="newMessage" (keyup.enter)="submitMessage()"></textarea>
</div>
and the code:
import { AfterViewChecked, ElementRef, ViewChild, Component, OnInit } from '#angular/core';
import {AuthService} from "../auth.service";
import 'rxjs/add/operator/catch';
import 'rxjs/add/operator/map';
import 'rxjs/add/operator/switchMap';
import 'rxjs/add/operator/concatAll';
import {Observable} from 'rxjs/Rx';
import { Router, ActivatedRoute } from '#angular/router';
#Component({
selector: 'app-messages',
templateUrl: './messages.component.html',
styleUrls: ['./messages.component.scss']
})
export class MessagesComponent implements OnInit {
#ViewChild('scrollMe') private myScrollContainer: ElementRef;
messages:Array<MessageModel>
newMessage = ''
id = ''
conversations: Array<ConversationModel>
profile: ViewMyProfileModel
disableScrollDown = false
constructor(private authService:AuthService,
private route:ActivatedRoute,
private router:Router,
private conversationsApi:ConversationsApi) {
}
ngOnInit() {
}
public submitMessage() {
}
ngAfterViewChecked() {
this.scrollToBottom();
}
private onScroll() {
let element = this.myScrollContainer.nativeElement
let atBottom = element.scrollHeight - element.scrollTop === element.clientHeight
if (this.disableScrollDown && atBottom) {
this.disableScrollDown = false
} else {
this.disableScrollDown = true
}
}
private scrollToBottom(): void {
if (this.disableScrollDown) {
return
}
try {
this.myScrollContainer.nativeElement.scrollTop = this.myScrollContainer.nativeElement.scrollHeight;
} catch(err) { }
}
}
Consider using
.scrollIntoView()
See https://developer.mozilla.org/en-US/docs/Web/API/Element/scrollIntoView
If you want to be sure, that you are scrolling to the end after *ngFor is done, you can use this.
<div #myList>
<div *ngFor="let item of items; let last = last">
{{item.title}}
{{last ? scrollToBottom() : ''}}
</div>
</div>
scrollToBottom() {
this.myList.nativeElement.scrollTop = this.myList.nativeElement.scrollHeight;
}
Important here, the "last" variable defines if you are currently at the last item, so you can trigger the "scrollToBottom" method
this.contentList.nativeElement.scrollTo({left: 0 , top: this.contentList.nativeElement.scrollHeight, behavior: 'smooth'});
If you are in recent version of Angular, following is enough:
<div #scrollMe style="overflow: scroll; height: xyz;" [scrollTop]="scrollMe.scrollHeight>
<div class="..."
*ngFor="..."
...>
</div>
</div>
const element = document.getElementById('box');
element.scrollIntoView({ behavior: 'smooth', block: 'end', inline: 'nearest' });
Vivek's answer has worked for me, but resulted in an expression has changed after it was checked error. None of the comments worked for me, but what I did was change the change detection strategy.
import { Component, ChangeDetectionStrategy } from '#angular/core';
#Component({
changeDetection: ChangeDetectionStrategy.OnPush,
selector: 'page1',
templateUrl: 'page1.html',
})
The title of the question mentions "Chat Style" scroll to bottom, which I also needed. None of these answers really satisfied me, because what I really wanted to do was scroll to the bottom of my div whenever child elements were added or destroyed. I ended up doing that with this very simple Directive that leverages the MutationObserver API
#Directive({
selector: '[pinScroll]',
})
export class PinScrollDirective implements OnInit, OnDestroy {
private observer = new MutationObserver(() => {
this.scrollToPin();
});
constructor(private el: ElementRef) {}
ngOnInit() {
this.observer.observe(this.el.nativeElement, {
childList: true,
});
}
ngOnDestroy() {
this.observer.disconnect();
}
private scrollToPin() {
this.el.nativeElement.scrollTop = this.el.nativeElement.scrollHeight;
}
}
You just attach this directive to your list element, and it will scroll to the bottom whenever a list item changes in the DOM. It's the behavior I was personally looking for. This directive assumes that you are already handling height and overflow rules on the list element.
Sharing my solution, because I was not completely satisfied with the rest. My problem with AfterViewChecked is that sometimes I'm scrolling up, and for some reason, this life hook gets called and it scrolls me down even if there were no new messages. I tried using OnChanges but this was an issue, which lead me to this solution. Unfortunately, using only DoCheck, it was scrolling down before the messages were rendered, which was not useful either, so I combined them so that DoCheck is basically indicating AfterViewChecked if it should call scrollToBottom.
Happy to receive feedback.
export class ChatComponent implements DoCheck, AfterViewChecked {
#Input() public messages: Message[] = [];
#ViewChild('scrollable') private scrollable: ElementRef;
private shouldScrollDown: boolean;
private iterableDiffer;
constructor(private iterableDiffers: IterableDiffers) {
this.iterableDiffer = this.iterableDiffers.find([]).create(null);
}
ngDoCheck(): void {
if (this.iterableDiffer.diff(this.messages)) {
this.numberOfMessagesChanged = true;
}
}
ngAfterViewChecked(): void {
const isScrolledDown = Math.abs(this.scrollable.nativeElement.scrollHeight - this.scrollable.nativeElement.scrollTop - this.scrollable.nativeElement.clientHeight) <= 3.0;
if (this.numberOfMessagesChanged && !isScrolledDown) {
this.scrollToBottom();
this.numberOfMessagesChanged = false;
}
}
scrollToBottom() {
try {
this.scrollable.nativeElement.scrollTop = this.scrollable.nativeElement.scrollHeight;
} catch (e) {
console.error(e);
}
}
}
chat.component.html
<div class="chat-wrapper">
<div class="chat-messages-holder" #scrollable>
<app-chat-message *ngFor="let message of messages" [message]="message">
</app-chat-message>
</div>
<div class="chat-input-holder">
<app-chat-input (send)="onSend($event)"></app-chat-input>
</div>
</div>
chat.component.sass
.chat-wrapper
display: flex
justify-content: center
align-items: center
flex-direction: column
height: 100%
.chat-messages-holder
overflow-y: scroll !important
overflow-x: hidden
width: 100%
height: 100%
Here's another good solution on stackblitz.
Alternatively:
The accepted answer is a good solution, but it can be improved since your content/chat may often scroll to the bottom involuntarily given how the ngAfterViewChecked() lifecycle hook works.
Here's an improved version...
COMPONENT
import {..., AfterViewChecked, ElementRef, ViewChild, OnInit} from 'angular2/core'
#Component({
...
})
export class ChannelComponent implements OnInit, AfterViewChecked {
#ViewChild('scrollMe') private myScrollContainer: ElementRef;
/**Add the variable**/
scrolledToBottom = false;
ngAfterViewChecked() {
this.scrollToBottom();
}
scrollToBottom(): void {
try {
/**Add the condition**/
if(!this.scrolledToBottom){
this.myScrollContainer.nativeElement.scrollTop = this.myScrollContainer.nativeElement.scrollHeight;
}
} catch(err) { }
}
/**Add the method**/
onScroll(){
this.scrolledToBottom = true;
}
}
TEMPLATE
<!--Add a scroll event listener-->
<div #scrollMe
style="overflow: scroll; height: xyz;"
(scroll)="onScroll()">
<div class="..."
*ngFor="..."
...>
</div>
</div>
In angular using material design sidenav I had to use the following:
let ele = document.getElementsByClassName('md-sidenav-content');
let eleArray = <Element[]>Array.prototype.slice.call(ele);
eleArray.map( val => {
val.scrollTop = val.scrollHeight;
});
In case anyone has this problem with Angular 9, this is how I manage to fix it.
I started with the solution with #scrollMe [scrollTop]="scrollMe.scrollHeight" and I got the ExpressionChangedAfterItHasBeenCheckedError error as people mentioned.
In order to fix this one I just add in my ts component:
#Component({
changeDetection: ChangeDetectionStrategy.OnPush,
...})
constructor(private cdref: ChangeDetectorRef) {}
ngAfterContentChecked() {
this.cdref.detectChanges();
}
ExpressionChangedAfterItHasBeenCheckedError: Expression has changed after it was checked. Previous value: 'undefined'
After reading other solutions, the best solution I can think of, so you run only what you need is the following:
You use ngOnChanges to detect the proper change
ngOnChanges() {
if (changes.messages) {
let chng = changes.messages;
let cur = chng.currentValue;
let prev = chng.previousValue;
if(cur && prev) {
// lazy load case
if (cur[0].id != prev[0].id) {
this.lazyLoadHappened = true;
}
// new message
if (cur[cur.length -1].id != prev[prev.length -1].id) {
this.newMessageHappened = true;
}
}
}
}
And you use ngAfterViewChecked to actually enforce the change before it renders but after the full height is calculated
ngAfterViewChecked(): void {
if(this.newMessageHappened) {
this.scrollToBottom();
this.newMessageHappened = false;
}
else if(this.lazyLoadHappened) {
// keep the same scroll
this.lazyLoadHappened = false
}
}
If you are wondering how to implement scrollToBottom
#ViewChild('scrollWrapper') private scrollWrapper: ElementRef;
scrollToBottom(){
try {
this.scrollWrapper.nativeElement.scrollTop = this.scrollWrapper.nativeElement.scrollHeight;
} catch(err) { }
}
Just in case someone is using Ionic and Angular,
here is a link that uses a very simple code to do that king of scroll to bottom (or top) :
https://forum.ionicframework.com/t/scroll-content-to-top-bottom-using-ionic-4-solution/163048
To add smooth scroll do this
#scrollMe [scrollTop]="scrollMe.scrollHeight" style="scroll-behavior: smooth;"
and
this.cdref.detectChanges();

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