I have two table rows at an HTML file. When the first row gets clicked, it changes its styling via classes.add("active_style"). If the second row gets clicked, I would like to clear the first row styling.
I know that I can just write...
querySelector("#first_row_div").classes.clear();
... in order to clear the first row class (and then resetting its style), but in a bigger code I think that observable would be the best fit.
I don't know if observable works for this. But, if it does, how can I do that?
EDIT/UPDATE: I think that the right question is "is there any way to run a function when a variable gets changed?".
Thanks for the help!
You can make a getter/setter for a field and run your function in the setter.
class MyClass {
String _cssClass;
String get cssClass => _cssClass;
set cssClass(String newClass) {
_cssClass = newClass;
updateDom();
}
void updateDom() {
// do important work here
}
}
You can use a model class that extends Observable.
Here you have to call dirtyCheck() to make Observable check for changes and notify listeners.
Dart also offers the ChangeNotifier mixin. Here you don't need to call any method for dirty-checking. When changes are made listeners are invoked.
A simple example I wrote a while ago while examining the functionality
import 'package:observe/observe.dart';
class Notifiable extends Object with ChangeNotifier {
String _input = '';
#reflectable
get input => _input;
#reflectable
set input(val) {
_input = notifyPropertyChange(#input, _input, val + " new");
}
Notifiable() {
this.changes.listen((List<ChangeRecord> record) => record.forEach(print));
}
}
class MyObservable extends Observable {
#observable
String counter = '';
MyObservable() {
this.changes.listen((List<ChangeRecord> record) => record.forEach(print));
}
}
void main() {
var x = new MyObservable();
x.counter = "hallo";
Observable.dirtyCheck();
Notifiable notifiable = new Notifiable();
notifiable.input = 'xxx';
notifiable.input = 'yyy';
}
Related
I want to double click on any row to getting respective row values. It is an .Razor page.
First of all, I would create a component that will inherit from QuickGrid, so you can manage it easier in the future.
// CustomGrid.razor.cs
[CascadingTypeParameter( nameof(TGridItem) )]
public partial class CustomGrid<TGridItem> : QuickGrid<TGridItem>, IAsyncDisposable
{
[Inject]
private IJSRuntime JS { get; set; } // inject service in order to use JS interop
// sometimes it is mandatory to override base class parameters by your own
}
// CustomGrid.razor
#using Microsoft.AspNetCore.Components.QuickGrid // move it into the _Imports.razor
#typeparam TGridItem // QuickGrid is a generic-typed component
#inherits QuickGrid<TGridItem> // show inheritance
<div #ref="#_gridRef"> // HTML reference of current element
<QuickGrid TGridItem="TGridItem"
Items="#Items"
ItemsProvider="#ItemsProvider"
ChildContent="#ChildContent"
Class="#Class"
// more parameters... >
</QuickGrid>
</div>
Since there is no built-in functionality for adding your custom logic into QuickGrid, you will need to use some JavaScript interopability. Read about it more in docs here and here.
We need to declare some local variables in our CustomGrid.razor.cs:
private string? _rowValue; // specifies row value of currently double clicked row
private ElementReference _gridRef; // HTML element reference object that will be passed to JS function
private IJSObjectReference? _module; // JS module, a file that contains our JS functions
private DotNetObjectReference<CustomGrid<TGridItem>>? _objRef; // .NET object reference that will be passed to JS function in order to use its C# methods
And override some of the component lifecycle methods:
protected override void OnInitialized()
{
_objRef = DotNetObjectReference.Create( this ); // creates .NET object reference of current component instance
}
protected override async Task OnAfterRenderAsync( bool firstRender )
{
if( firstRender )
{
_module = await JS.InvokeAsync<IJSObjectReference>( "import", "./js/customGrid.js" ); // creates a reference of our JS module
if( _module is not null )
{
await _module.InvokeVoidAsync( "initialize", _gridRef, _objRef ); // calls our JS function and passes some arguments
}
}
}
Now, you need to create a JS module and a functions that will add desired logic for you on the first render of the CustomGrid component, like this:
// wwwroot/js/customGrid.js
export function initialize(customGrid, dotNetObj) {
if (customGrid) { // check if custom grid element exists
var rowValue;
const rows = customGrid.querySelectorAll('tbody > tr'); // get all rows except the header row
for (let i = 0; i < rows.length; i++) {
rows[i].addEventListener('dblclick', (e) => { // add event listener to current row in the loop
rowValue = e.path[1].innerText; // get innerText of current row in the loop
console.log(rowValue)
updateCurrentRowValue(rowValue, dotNetObj); // function that will return the current row value and refresh the UI
});
}
}
}
function updateCurrentRowValue(rowValue, dotNetObj) {
dotNetObj.invokeMethodAsync("UpdateCurrentRowValue", rowValue); // C# method
}
We're almost done here! If you would try to perform double click on the row, you would see an error in the console stating that CustomGrid does not contain a public method called UpdateCurrentRowValue. Let's add it like this:
[JSInvokable]
public void UpdateCurrentRowValue( string rowValue )
{
_rowValue = rowValue; // assign received rowValue from the JS function to our local _rowValue variable
StateHasChanged(); // force UI refresh
}
Now, all you need to do is to display your _rowValue:
// CustomGrid.razor
<div #ref="#_gridRef">
<QuickGrid TGridItem="TGridItem" . . . /> // collapsed for brevity
<p>Current Row Value: #_rowValue</p>
</div>
You will also need to Dispose your newly created objects of _module and _objRef using IAsyncDisposable.DisposeAsync method:
// CustomGrid.razor.cs
async ValueTask IAsyncDisposable.DisposeAsync()
{
if( _module is not null )
{
await _module.DisposeAsync();
}
_objRef?.Dispose();
}
Usage:
<CustomGrid Items="#people">
<PropertyColumn Property="#(p => p.PersonId)" Sortable="true" />
<PropertyColumn Property="#(p => p.Name)" Sortable="true" />
<PropertyColumn Property="#(p => p.BirthDate)" Format="yyyy-MM-dd" Sortable="true" />
</CustomGrid>
That should work. If you will need any help -- don't hesitate to ask!
Remarks:
This is a basic implementation of your request. It doesn't support scenarios when there are more than 1 grid on the page. It might work, but will be buggy, I guess. For that, you will need to add some more code in JS and CustomGrid code-behind. I didn't add it because it would be too much code in one answer (quite a lot of code came out here anyway).
UPD-1:
Removed custom [Parameter]s to override QuickGrid's ones and added a comment.
I am trying to get a class to have a property bound to another class's list property, where the 1st property is derived from a summarizing calculation over the objects in the list. The code below is a simplified version of my production code. (The production code is doing a summary over DateTime objects -- the essential part of the code below is the binding between a list and an object property (here, it is a String for simplicity).)
I have tried various things. One approach was using addListener on the list in the Summary class below but I was running into weird bugs with the listener callback making updates on the Summary object. After doing a bunch of reading I think that a binding between the summary string and the list is more appropriate but I don't know exactly how to hook up the binding to the property?
package com.example.demo.view
import javafx.beans.Observable
import javafx.beans.binding.StringBinding
import javafx.beans.property.SimpleIntegerProperty
import javafx.beans.property.SimpleListProperty
import javafx.beans.property.SimpleStringProperty
import javafx.collections.FXCollections
import tornadofx.View
import tornadofx.button
import tornadofx.label
import tornadofx.vbox
class Thing(x: Int) {
val xProperty = SimpleIntegerProperty(x)
val yProperty = SimpleStringProperty("xyz")
}
class Collection {
private var things = FXCollections.observableList(mutableListOf<Thing>()) {
arrayOf<Observable>(it.xProperty)
}
val thingsProperty = SimpleListProperty<Thing>(things)
fun addThing(thing: Thing) {
things.add(thing)
}
}
class Summary(var collection: Collection) {
val summaryBinding = object : StringBinding() {
// The real code is more practical but
// this is just a minimal example.
override fun computeValue(): String {
val sum = collection.thingsProperty.value
.map { it.xProperty.value }
.fold(0, { total, next -> total + next })
return "There are $sum things."
}
}
// How to make this property update when collection changes?
val summaryProperty = SimpleStringProperty("There are ? things.")
}
class MainView : View() {
val summary = Summary(Collection())
override val root = vbox {
label(summary.summaryProperty)
button("Add Thing") {
summary.collection.addThing(Thing(5))
}
}
}
Keep in mind that I made this answer based on your minimal example:
class Thing(x: Int) {
val xProperty = SimpleIntegerProperty(x)
var x by xProperty
val yProperty = SimpleStringProperty("xyz")
var y by yProperty
}
class MainView : View() {
val things = FXCollections.observableList(mutableListOf<Thing>()) {
arrayOf<Observable>(it.xProperty)
}
val thingsProperty = SimpleListProperty<Thing>(things)
val totalBinding = integerBinding(listProperty) {
value.map { it.x }.fold(0, { total, next -> total + next })
}
val phraseBinding = stringBinding(totalBinding) { "There are $value things." }
override val root = vbox {
label(phraseBinding)
button("Add Thing") {
action {
list.add(Thing(5))
}
}
}
}
I removed your other classes because I didn't see a reason for them based on the example. If the collection class has more functionality than holding a list property in your real project, then add just add it back in. If not, then there's no reason to give a list its own class. The summary class is really just two bindings (or one if you have no need to separate the total from the phrase). I don't see the need to give them their own class either unless you plan on using them in multiple views.
I think your biggest problem is that you didn't wrap your button's action in action {}. So your code just added a Thing(5) on init and had no action set.
P.S. The var x by xProperty stuff will only work if you import tornadofx.* for that file.
I'd like to make wrapper to implement simple data binding pattern -- while some data have been modified all registered handlers are got notified. I have started with this (for js target):
class Main {
public static function main() {
var target = new Some();
var binding = new Bindable(target);
binding.one = 5;
// binding.two = 0.12; // intentionally unset field
binding.three = []; // wrong type
binding.four = 'str'; // no such field in wrapped class
trace(binding.one, binding.two, binding.three, binding.four, binding.five);
// outputs: 5, null, [], str, null
trace(target.one, target.two, target.three);
// outputs: 5, null, []
}
}
class Some {
public var one:Int;
public var two:Float;
public var three:Bool;
public function new() {}
}
abstract Bindable<TClass>(TClass) {
public inline function new(source) { this = source; }
#:op(a.b) public function setField<T>(name:String, value:T) {
Reflect.setField(this, name, value);
// TODO notify handlers
return value;
}
#:op(a.b) public function getField<T>(name:String):T {
return cast Reflect.field(this, name);
}
}
So I have some frustrating issues: interface of wrapped object doesn't expose to wrapper, so there's no auto completion or strict type checking, some necessary attributes can be easily omitted or even misspelled.
Is it possible to fix my solution or should I better move to the macros?
I almost suggested here to open an issue regarding this problem. Because some time ago, there was a #:followWithAbstracts meta available for abstracts, which could be (or maybe was?) used to forward fields and call #:op(a.b) at the same time. But that's not really necessary, Haxe is powerful enough already.
abstract Binding<TClass>(TClass) {
public function new(source:TClass) { this = source; }
#:op(a.b) public function setField<T>(name:String, value:T) {
Reflect.setField(this, name, value);
// TODO notify handlers
trace("set: $name -> $value");
return value;
}
#:op(a.b) public function getField<T>(name:String):T {
trace("get: $name");
return cast Reflect.field(this, name);
}
}
#:forward
#:multiType
abstract Bindable<TClass>(TClass) {
public function new(source:TClass);
#:to function to(t:TClass) return new Binding(t);
}
We use here multiType abstract to forward fields, but resolved type is actually regular abstract. In effect, you have completion working and #:op(a.b) called at the same time.
You need #:forward meta on your abstract. However, this will not make auto-completion working unless you remove #:op(A.B) because it shadows forwarded fields.
EDIT: it seems that shadowing happened first time I added #:forward to your abstract, afterwards auto-completion worked just fine.
I am trying to make a simple mp3 player using flash. The songs are loaded using an XML file which contains the song list. I have "play" button with the instance name "PlayBtn". I have an actionscript file named "playctrl", the content of which are listed below:
package classes
{
import flash.media.Sound;
import flash.media.SoundChannel;
import flash.events.*;
import flash.events.MouseEvent;
import flash.net.URLRequest;
public class playctrl
{
private var MusicLoading:URLRequest;
private var music:Sound;
private var sc:SoundChannel;
private var currentSound:Sound;
private static var CurrentPos:Number;
private var xml:XML;
private var songlist:XMLList;
private static var currentIndex:Number;
public function playctrl()
{
music = new Sound();
currentSound= music;
CurrentPos = 0;
currentIndex = 0;
}
public function success(e:Event):void
{
xml = new XML(e.target.data);
songlist = xml.song;
MusicLoading = new URLRequest(songlist[0].file);
music.load(MusicLoading);
}
public function playSong(e:Event):void
{
if(sc != null)
sc.stop();
sc = currentSound.play(CurrentPos);
trace("HELLO !!!");
}
}
}
I have a second file named "play.as", the content of which is listed below:
import classes.playctrl;
var obj:playctrl = new playctrl();
var XMLLoader:URLLoader = new URLLoader(); //XML Loader
XMLLoader.addEventListener(Event.COMPLETE, obj.success);
XMLLoader.load(new URLRequest("playlist.xml"));
PlayBtn.addEventListener(MouseEvent.CLICK, obj.playSong);
However on clicking the play button, I notice that the function playSong() is called 7-8 times(check by printing an error msg. inside the function) resulting in overlapped audio output and the player crashing as a result. The function should be called only once when the MouseEvent.CLICK is triggered. Please help ...
interestingly, sound object doesn't have a built-in "isPlaying" boolean property (strange), so you could just create your own.
var isPlaying:Boolean
function playSong():void
{
if(!isPlaying)
sound.play();
}
function stopSong():void
{
if(isPlaying)
{
channel.stop();
isPlaying = false;
}
just a note: by convention, class names are capitalized camel case while instance names are uncapitalized camel case. so your playctrl.as class file should (or could) be PlayCtrl.as, and your PlayBtn instance should (or could) be playBtn.
Edit:
The title of your question is a bit misleading, the answer I gave you is a solution to the question expressed in the title.
Looking at your code, I would look at separating the concerns, on one hand you want to load the song data, on the other hand you want to control the sounds. I would implement separate classes for each concern. If you create a separate class for your player control, you'll be able to dispatch event within that class without the event bubbling all over your app and calling your functions several times.
//Previous answer
You could do this by implementing a Boolean that would be set when the sound is stopped or played.
In any case here's another way to filter unwanted clicks
private function playSong(event:MouseEvent ):void
{
// set up a conditional to identify your button ,
// here's an example...
if( event.currentTarget.name is "PlayBtn" )
{
//do whatever
//then...
event.stopImmediatePropagation();
}
}
This being said, in your case , it sounds like a bit of a quick fix since a MouseEvent shouldn't trigger the play function several times...
It would make sense to debug your code in order to understand why several events are dispatched after a Mouse click
private var _isPlaying:Boolean;
public function playSong(e:Event):void
{
if(sc != null)
{
sc.stop();
_isPlaying = false;
}
if( !_isPlaying )
{
sc = currentSound.play(CurrentPos);
_isPlaying = true;
trace("HELLO !!!");
}
}
Can I somehow find out what was the change in the textfield? I would want to compare the old text with the new text ... the problem is, that I have multiple textAreas in a tab-editor, and all the textAreas are watched by one eventListener. I want to get a value calculated by the next formula:
globalChangeCount += thisTextArea.currentCharacterCount - thisTextArea.oldtCharacterCount
where the globalChangeCount is a value modified by all changes in any of the textAreas.
I am searching for these values through the event variable, but can't seam to find the old text of the textArea.
This may or may not be what you're looking to do:
package
{
import mx.controls.TextArea;
public class CountingTextArea extends TextArea
{
public var staleText : String = "";
[Bindable("textChanged")]
[NonCommittingChangeEvent("change")]
public function get charDiff() : int
{
var diff : int = staleText.length - text.length;
staleText = text;
return diff;
}
public function CountingTextArea()
{
super();
}
}
}
I made it so that you can use it as a source for binding. Instead of subscribing to the event on each TextArea, you can use:
function addWatchers():void
{
ChangeWatcher.watch(countingTextArea1, ["charDiff"], charDiffChangeHandler );
...
ChangeWatcher.watch(countingTextArea5, ["charDiff"], charDiffChangeHandler );
}
With the event handler somewhere too:
function charDiffChangeHandler( event : PropertyChangeEvent ) : void
{
trace(event.currentTarget.charDiff);
// or
trace(event.newValue);
}
You can use event.currentTarget to get a reference to the TextArea that fired the event, and use the focusIn event to execute a function to populate a variable with the old text value.
Maybe you should just subclass the TextArea and create an oldText field variable you update internally after all the external listeners have been notified.