I have a dom-repeat which displays a large list of items (about 9000 of them).
I am trying to only display part of the items, so that I don't end up with a gigantic scrollbar. For that I am using a dom-if that only shows items that have an index larger than 10.
When the dom-repeat is sorted or filtered, each item's index is recalculated, so it works very well.
Then I am using iron-scroll-threshold to detect when the user has scrolled to the bottom of the page, and then I am increasing the number of items displayed.
The problem is, this is not recalculating the index - in other words I can't figure out how to "redraw" the dom-repeat.
Is there a way to force a dom-repeat to recalculate all the index? Calling this.$.list.render() doesn't seem to do it.
<template id="list" is="dom-repeat" id="table" items="{{items}}" sort="{{sortFuntion}}">
<template is="dom-if" if="{{isShowItem(index)}}">
[[item.name]]<br />
</template>
</template>
<iron-scroll-threshold scroll-target="document" on-lower-threshold="showMoreData">
</iron-scroll-threshold>
<script>
Polymer({
is: 'my-element',
properties: {
limit: {type: Number, value: 10}
},
isShowItem: function(index) {
return (index < this.limit);
// we only show the items that have an index smaller than "limit"
// (the index is recalculated for each sort or filter, so it works well).
},
showMoreData: function() {
// this is called by iron-scroll-threshold when we scroll down the page
this.set("limit", this.limit + 10);
// this is what doesn't seem to do anything:
// (ideally we want it to recalculate each item's index)
this.$.list.render();
}
});
</script>
I never use filter or sort in a dom-repeat but instead insert a method in items. Then I can control all sorts of stuff.
<template id="list" is="dom-repeat" id="table" items="[[_filterItems(items, scrollHeight)]]" sort="[[sortFuntion]]">
##code
</template>
---
<script>
Polymer({
## properties and other methods
_filterItems(items, scrollHeight) { // ex. scrollHeight = 100
var interpolationLevel = 5; // px
var minAllowedItems = 10;
var showThisManyItems = scrollHeight / interpolationLevel; // 100 / 5
showThisManyItems (showThisManyItems < minAllowedItems) ? minAllowedItems : showThisManyItems; // 100 / 5 = 20, but min value == 10
return items.filter(item, index) {
return index < showThisManyItems; // show this item if index < 20
}
},
}
</script>