I am trying to create an E-commerce Store and I'm a beginner in React.JS. What I want is for 5 images to come together on top of eachother when the user scrolls. (so they should move TranslateX on scroll). Previously, on Vanilla Javascript I would have added a window.addEventListener('scroll') and then set a value like value = window.scrollY and then I would have selected the image I wanted to move and simply translateX or Y based on that value.
However, I'm not sure how to do this in React. Where can I set the window event listener? Is there a state needed, or useEffect?
I'm attaching an image so you can clearly see what I am trying to do:
What I have in react is the "Scroll" component which contains 2 divs
-1 div on the left 2/3 flex size containing all the images that should come together
-1 div on the right 1/3 flex size containing the text and the button
inside the left div I have 5 images, and in CSS i've used position absolute to position them on top of eachother (they are all PNGs so they have transparent background).
How would I go about implementing this on my website?
HUGE thanks in advance!
You can save the scrollY in a useState, which you then use to transofrm your images. The window listeners can be loaded inside a useEffect.
It (could) look like this:
const [scrollY, setScrollY] = useState(0);
useEffect(() => {
const handleScroll = () => {
setScrollY(window.scrollY);
};
handleScroll();
window.addEventListener("scroll", handleScroll);
return () => {
window.removeEventListener("scroll", handleScroll);
};
}, []);
(You may have to add some ESLint rules if you use it)
I am conceiving a horizontal bar containing items.
They must all be of same width, having the same spacing between them.
They can expand as much as they want vertically (
stackblitz here
Problem:
How to automatically set the width of the row elements? Here I simply put a value that looks good: width:200px.
I want them to have a width dependent on the number of element per row.
What I tried:
Using elementRef in Horizontile (component holding the individual tiles, displaying with *ngFor) to get the width of this element:
currentWidth:number;
constructor(private el:ElementRef) {}
ngAfterViewInit(): void {
this.currentWidth=this.el.nativeElement.offsetWidth;}
it returns 5. (??) Using .width returns nothing. Also this is not recommended, I'd like another solution, less coupling.
I noticed I can make use of width:inherit; in the css of the individual tile component, which allows me to set the style from the horizontal list component.
<app-tile [style.width.px]="0.9*currentWidth/nDisplayedTiles" [tile]="item"></app-tile>
As the currentWidth value is zero, of course it doesn't work;
I tried setting it in % but the inherits css tag keeps the %, which is not the intended effect.
Why is the app-tile styling not cared about if inherits is not set?
I tried using ViewEncapsulation but it had no effect either.
This looks like a trivial matter though: did I just miss something?
You can use the offsetParent (link) width and create a method to return the value on each of the cells and call it in your [style.width.px], something like the following will work.
The HTMLElement.offsetParent read-only property returns a reference to the element which is the closest (nearest in the containment hierarchy) positioned ancestor element.
stackblitz
ngAfterViewInit(): void {
//added this as the compiler was throwing ExpressionChangedAfterItHasBeenCheckedError
setTimeout(() => {
this.currentWidth=this.el.nativeElement.offsetParent.clientWidth;
});
}
getWidth(): number{
let width:number = 0;
//you may need to change this value to better display the cells
let multiplier = 0.7;
width = (this.currentWidth * multiplier) / this.ndisplayTiles;
width = Math.round(width);
return width;
}
<app-tile [class]="'layout-tile'" [tile]="item" [style.width.px]="getWidth()">
</app-tile>
This is the code I've found to retrieve the correct draggable element and edit it's dimensions, during the onBeforeCapture() responder. Changing dimensions during this responder is in accordance with the documentation. This seems to work in only changing the dimensions, the other problems is that I am using the renderClone method, and so the draggable is just dragging with a huge offset that is not close to the correct mouse position. Also dnd is treating the drop placeholder as if the draggable is the original large size. Is there any way to correct for this mouse position, and placeholder dimensions? I've looked into adding mouseDown/mouseUp handlers on the inner element of the draggable but that doesn't seem to work either.
const cardSize = 140;
const draggableAttr = "data-rbd-drag-handle-draggable-id";
const getAttr = (key: string, value: string) => `[${key}=${value}]`;
const draggableQuery = getAttr(draggableAttr, update.draggableId);
const draggable = document.querySelector(draggableQuery);
draggable.setAttribute("style", `width: ${cardSize}px; height: ${cardSize}px;`);
I noticed onBeforeCapture was triggering after onDragEnd (therefore resizing the draggable improperly), so I created some state to remember the last beforeCaptureResult and return if it is equivalent to the current result.
I'm trying to create a scroll implementation similar to Facebook's feed in the way that they conditionally lock the side bars. For example if the content in the side bars is shorter than the viewport then the side bars don't scroll. If it does need to scroll, then it scrolls until the bottom of the side bar and stops at the end(all while allowing the center feed to keep scrolling)
The good part, I have almost all of this done, except for a few small issues and conditionally locking the side bars when they are fully in view.
The side bar contains quite a bit of data, and changes dynamically in height after everything is fetched. So my plan is below:
componentDidUpdate(prevProps) {
const leftSideBar = this.leftSideBar.current;
const scrollableWindow = window.innerHeight;
const sideBarHeight = leftSideBar.scrollHeight;
let offset = sideBarHeight - scrollableWindow;
if (this.state.offset !== offset) {
this.setState({ offset: offset });
if (offset > 0) {
this.setState({ lockScroll: false });
} else {
this.setState({ lockScroll: true });
}
}
}
This seems to be working inconsistently, sometimes the sideBarHeight is incorrect and I think it is because the component is updated and I'm getting that value before it is rendered and the height changes?
Basically I'm wondering if there is a better approach to this?
Let me start with i am sorry for the long post.
I'm attempting to use the bootstrap carousel and unfortunately the pictures i have been given are NOT uniform. for example some are 100x200, doe are 150x100, etc. The aspect ratios are different, letter vs landscape. Ive attempted a number of things, including the using the following helper function on load of each of my images in the Carousel:
function ScaleImage(srcwidth, srcheight, targetwidth, targetheight, fLetterBox) {
var result = { width: 0, height: 0, fScaleToTargetWidth: true };
if ((srcwidth <= 0) || (srcheight <= 0) || (targetwidth <= 0) || (targetheight <= 0)) {
return result;
}
// scale to the target width
var scaleX1 = targetwidth;
var scaleY1 = (srcheight * targetwidth) / srcwidth;
// scale to the target height
var scaleX2 = (srcwidth * targetheight) / srcheight;
var scaleY2 = targetheight;
// now figure out which one we should use
var fScaleOnWidth = (scaleX2 > targetwidth);
if (fScaleOnWidth) {
fScaleOnWidth = fLetterBox;
}
else {
fScaleOnWidth = !fLetterBox;
}
if (fScaleOnWidth) {
result.width = Math.floor(scaleX1);
result.height = Math.floor(scaleY1);
result.fScaleToTargetWidth = true;
}
else {
result.width = Math.floor(scaleX2);
result.height = Math.floor(scaleY2);
result.fScaleToTargetWidth = false;
}
result.targetleft = Math.floor((targetwidth - result.width) / 2);
result.targettop = Math.floor((targetheight - result.height) / 2);
return result;
}
function OnImageLoad(evt) {
var img = evt.currentTarget;
// what's the size of this image and it's parent
var w = $(img).prop('naturalWidth');
var h = $(img).prop('naturalHeight');
//var tw = $(img).parent().width();
//var th = $(img).parent().height();
var tw = $(img).parent().parent().parent().parent().width();
var th = $(img).parent().parent().parent().parent().height();
// compute the new size and offsets
var result = ScaleImage(w, h, tw, th, true);
// adjust the image coordinates and size
img.width = result.width;
img.height = result.height;
$(img).css("left", result.targetleft);
$(img).css("top", result.targettop);
}
and using the following for each of my images for the carousel
<img src="~/Images/Img1_Tall.jpg" alt="Tall" id="firstImage" onload="OnImageLoad(event);" />
and for the FIRST image in the carousel it works great, but each one after that they seem to just end up their natural size and are horizontally centered but are just against the top boarder of the carousel.
I've even changed the "onload" to pass the values of the length and width of the image but that didn't work either, in debug it seems only the first image kicks off the "onload" event.
the effect i am going for is if the ratio of the container is 3:4 and the ratio of the image is 1:2, the image stretch to meet the left and right edges and would center vertically and have letter box above and below, but the container does not change so that the navigation buttons of the carousel do not move. if the image is 2:1, the image would stretch to meet the top and bottom centered horizontally with letterboxes on the right and left, again keeping the navigation buttons unmoved.
any help would be appreciated... including:
what you are trying to do is crazy
do you want to do something like http://jsbin.com/zotelasa/1 . With that code I can get the active items w,h or any other variables you used in your code to run scale image. Because of parent.parent codes it applies to carousels main divs but you can set your own container.
The quick and dirty solution would be to resize the images using an image editor, and save the properly-sized images to a folder named eg carousel_images. Then whenever you get new content you simply run the image through your editor. With a carousel you're most likely dealing with a number of images in the several to dozens range and not hundreds or thousands.
A more complicated solution is explain to your image provider that you need everything one size. The images aren't going to look right if you're stretching and skewing them on the fly, and you can show them an image with the aspect ratios wrong to explain what you mean.
Finally, as a technical solution, I would try to find out why your image resizer is only being run on the first image. From the sound of it, other images just aren't being run through your function. I think that the technical solution should be a last resort in this case because, like I said, the end results are just not going to be as good. You should at a minimum, if possible, handle each image by hand to make sure the result is adequate.
...And the answer is a little long too...
• I assume that the width’s image’s parent is a constant, and while you don’t change the width’s viewport that must remain.
A-. Get the width’s image’s parent…
(Because the id attribute I took the grand parent’s parameter, that is (must be) the same than the parent’s one).
B-. With the below value deduce the height’s image’s parent, including the preferred ratio (in this case 16x9…
C-. … And with this, set the images’ parents height collection (all the elements with class=”item”).
D-. In order to conserve your carousel’s responsive characteristic, you must add the $F_getAdjustImagesParents function to the window resize event.
E-. Set the slide’s images position to absolute (Note: That must be via JQuery because if you do it in Css the bootstrap carousel will not display correctly. I did it with a new class for the images ('myCarouselImgs').
• Bootstrap carousel’s event 'slide.bs.carousel' and 'slid.bs.carousel'.
As you know, after the ‘click’ event, the slide.bs.carousel event is one of the firsts events that imply the change from the present slide to the next one; while the 'slid.bs.carousel' one is the end of the process.
F-. In the first one (slide.bs.carousel event), using the ‘relatedTarget’ variable of the Bootstrap’s plugin, the item’s id attribute and a item’s data attribute, get the number of the next item (ensure that these last ones -id attribute and data attribute- be present).
G-. In the second one, 'slid.bs.carousel', get the image’s size. For that you need to identify the implied image. I gave an id to each one. With this and the value obtained in previus step, it can do it.
H-. Well, now you already have the four values required for the ScaleImage function. You can call it…
I-. … And apply the result with some effect
var $parentImgW = ' '
var $parentImgH = ' ';
var $myCarousel = $('#myCarousel')
var $carouseItems = $('.item');
function $F_getAdjustImagesParents(){
$parentImgW = $myCarousel.width(); // A
$parentImgH = ($parentImgW*9)/16; // B
$carouseItems.height($parentImgH+'px').css('max-height',$parentImgH+'px'); //C
console.log('$parentImgW ====> '+$parentImgW);
console.log('$parentImgH ====> '+$parentImgH)
};
$F_getAdjustImagesParents();
$(window).on('resize',function(){ // D
$F_getAdjustImagesParents();
});
$('.myCarouselImgs').css('position','absolute'); // E
$myCarousel.on('slide.bs.carousel', function(event) {// The slide’s change process starts
var $slideNum = $("#"+event.relatedTarget.id).data('slide_num'); // F
console.log('$lideNum ====> '+$slideNum)
$myCarousel.on('slid.bs.carousel', function(event) {//The slide’s change process ends
var $imgW = $('#myCarouselSlideImage'+$slideNum).width(); //G
var $imgH = $('#myCarouselSlideImage'+$slideNum).height(); //G
console.log('$imgW ====> '+$imgW);
console.log('$imgH ====> '+$imgH);
var $result = '';
$result = ScaleImage($imgW, $imgH, $parentImgW, $parentImgH, true); //H
console.log('$result.width ====> '+$result.width);
console.log('$result.height ====> '+$result.height);
console.log('$result.targetleft ====> '+$result.targetleft);
console.log('$result.targettop ====> '+$result.targettop);
$('#myCarouselSlideImage'+$slideNum).animate({ // I
width:$result.width+'px',
height:$result.height+'px',
left:$result.targetleft+'px',
top:$result.targettop+'px' },
300);
});
});
See it runnig at https://jsfiddle.net/nd90r1ht/57/ or at https://jsfiddle.net/omarlin25/nd90r1ht/59/