Ionic - JavaScript Scroll


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The element used for scrolling manipulation in ionic apps is called as the ion-scroll.

Using Scroll

The following code snippets will create scrollable containers and adjust scrolling patterns. First, we will create our HTML element and add properties to it. We will add → direction = "xy" to allow scrolling to every side. We will also set the width and the height for the scroll element.

HTML Code

<ion-scroll zooming = "true" direction = "xy" style = "width: 320px; height: 500px">
   <div class = "scroll-container"></div>
</ion-scroll>

Next, we will add the image of our world map to div element, which we created inside the ion-scroll and set its width and height.

CSS Code

.scroll-container {
   width: 2600px;
   height: 1000px;
   background: url('../img/world-map.png') no-repeat
}

When we run our app, we can scroll the map in every direction. The following example shows the North America part of the map.

Ionic Javascript Scroll Start

We can scroll this map to any part that we want. Let us scroll it to show Asia.

Ionic Javascript Scroll End

There are other attributes, which can be applied to the ion-scroll. You can check them in the following table.

Scroll Attributes

Attribute Type Details
direction string Possible directions of the scroll. Default value is y
delegate-handle string Used for scroll identification with $ionicScrollDelegate.
locking boolean Used to lock scrolling in one direction at a time. Default value is true.
paging boolean Used to determine if the paging will be used with scroll.
on-refresh expression Called on pull-to-refresh.
on-scroll expression Called when scrolling.
scrollbar-x boolean Should horizontal scroll bar be shown. Default value is true.
scrollbar-y string Should vertical scroll bar be shown. Default value is true.
zooming boolean Used to apply pinch-to-zoom.
min-zoom integer Minimal zoom value.
max-zoom integer Maximal zoom value.
scrollbar-x boolean Used to enable bouncing. Default value on IOS is true, on Android false.

Infinite Scroll

An Infinite scroll is used to trigger some behavior when scrolling passes the bottom of the page. The following example shows how this works. In our controller, we created a function for adding items to the list. These items will be added when a scroll passes 10% of the last element loaded. This will continue until we hit 30 loaded elements. Every time loading is finished, on-infinite will broadcast scroll.infiniteScrollComplete event.

HTML Code

<ion-list>
   <ion-item ng-repeat = "item in items" item = "item">Item {{ item.id }}</ion-item>
</ion-list>

<ion-infinite-scroll ng-if = "!noMoreItemsAvailable" on-infinite = "loadMore()" 
   distance = "10%"></ion-infinite-scroll>

Controller Code

.controller('MyCtrl', function($scope) {
   $scope.items = [];
   $scope.noMoreItemsAvailable = false;
   
   $scope.loadMore = function() {
      $scope.items.push({ id: $scope.items.length}); 

      if ($scope.items.length == 30) {
         $scope.noMoreItemsAvailable = true;
      }

      $scope.$broadcast('scroll.infiniteScrollComplete');
   };
})

Other attributes can also be used with ion-infinite-scroll. Some of them are listed in the table below.

Scroll Attributes

Attribute Type Details
on-infinite expression What should be called when scrolled to the bottom.
distance string The distance from the bottom needed to trigger on-infinite expression.
spinner string What spinner should be shown while loading
immediate-check Boolean Should ‘on-infinite’ be called when screen is loaded

Scroll Delegate

Ionic offers delegate for full control of the scroll elements. It can be used by injecting a $ionicScrollDelegate service to the controller, and then use the methods it provides.

The following example shows a scrollable list of 20 objects.

HTML Code

<div class = "list">
   <div class = "item">Item 1</div>
   <div class = "item">Item 2</div>
   <div class = "item">Item 3</div>
   <div class = "item">Item 4</div>
   <div class = "item">Item 5</div>
   <div class = "item">Item 6</div>
   <div class = "item">Item 7</div>
   <div class = "item">Item 8</div>
   <div class = "item">Item 9</div>
   <div class = "item">Item 10</div>
   <div class = "item">Item 11</div>
   <div class = "item">Item 12</div>
   <div class = "item">Item 13</div>
   <div class = "item">Item 14</div>
   <div class = "item">Item 15</div>
   <div class = "item">Item 16</div>
   <div class = "item">Item 17</div>
   <div class = "item">Item 18</div>
   <div class = "item">Item 19</div>
   <div class = "item">Item 20</div>
</div>

<button class = "button" ng-click = "scrollTop()">Scroll to Top!</button>

Controller Code

.controller('DashCtrl', function($scope, $ionicScrollDelegate) {

   $scope.scrollTop = function() {
      $ionicScrollDelegate.scrollTop();
   };
})   

The above code will produce the following screen −

Ionic Javascript Scroll Bottom

When we tap the button, the scroll will be moved to the top.

Ionic Javascript Scroll Top

Now, we will go through all of the $ionicScrollDelegate methods.

Delegate Methods

Method Parameters Type Details
scrollTop(parameter) shouldAnimate boolean Should scroll be animated.
scrollBottom(parameter) shouldAnimate boolean Should scroll be animated.
scrollTo(parameter1, parameter2, parameter3) left, top, shouldAnimate number, number, integer First two parameters determine value of the x, and y-axis offset.
scrollBy(parameter1, parameter2, parameter3) left, top, shouldAnimate number, number, integer First two parameters determine value of the x, and y-axis offset.
zoomTo(parameter1, parameter2, parameter3, parameter4) level, animate, originLeft, originTop number, boolean, number, number level is used to determine level to zoom to. originLeft and originRight coordinates where the zooming should happen.
zoomBy(parameter1, parameter2, parameter3, parameter4) factor, animate, originLeft, originTop number, boolean, number, number factor is used to determine factor to zoom by. originLeft and originRight coordinates where the zooming should happen.
getScrollPosition() / / Returns object with two number as properties: left and right. These numbers represent the distance the user has scrolled from the left and from the top respectively.
anchorScroll(parameter1) shouldAnimate boolean It will scroll to the element with the same id as the window.loaction.hash. If this element does not exist, it will scroll to the top.
freezeScroll(parameter1) shouldFreeze boolean Used to disable scrolling for particular scroll.
freezeAllScrolls(parameter1) shouldFreeze boolean Used to disable scrolling for all the scrolls in the app.
getScrollViews() / object Returns the scrollView object.
$getByHandle(parameter1) handle string

Used to connect methods to the particular scroll view with the same handle.

$ionicScrollDelegate. $getByHandle('my-handle').scrollTop();


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