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cmidt-viewpager.html
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cmidt-viewpager.html
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<link rel="import" href="../polymer/polymer.html">
<link rel="import" href="../iron-scroll-target-behavior/iron-scroll-target-behavior.html">
<link rel="import" href="../iron-scroll-threshold/iron-scroll-threshold.html">
<link rel="import" href="../iron-icon/iron-icon.html">
<link rel="import" href="../iron-flex-layout/iron-flex-layout.html">
<link rel="import" href="../iron-resizable-behavior/iron-resizable-behavior.html">
<link rel="import" href="../iron-selector/iron-selector.html">
<link rel="import" href="../paper-icon-button/paper-icon-button.html">
<link rel="import" href="cmidt-viewpager-icons.html">
<!--
The `cmidt-viewpager` is custom element, implement high Performance unlimit horizontal
page scroll like Android View Pager.
Example:
<cmidt-viewpager id="pager" items="[[array]]">
<template>
<div>....</div>
</template>
</cmidt-viewpager>
ViewPager required explicit size, width and height, it could be value of explicit pixel or 100%.
By default, ViewPager will adapted to the browser of the plaform, if the browser are running on the none touch device
such laptop or desktop, user can use mouse wheel to scroll and change the page if the OS support mouse wheel.
Computer like Macbook is working smoothly with mouse wheel. If the browser are running on device support touch event,
user can touch and move to change the page, however if the device support both feature then user can interact with both event.
<b>Note:</b> the mouse wheel feature may not work properly on Firefox browser as there is a small requirement to implement on
Javascript code for performance reason,
See https://developer.mozilla.org/en-US/docs/Mozilla/Performance/Scroll-linked_effects. ViewPager rely on `iron-scroll-target-behavior`
to perfrom scrolling on the container of the each page and the feature might need to be implemented in the behavior instead of ViewPager
### Styling
The following custom properties and mixins are available for styling:
Custom property | Description | Default
----------------|-------------|----------
`--cmidt-page`| Mixin style applied to the page | `{}`
`--cmidt-page-margin`| Margin or space between page, it include as padding | `0px`
`--cmidt-page-indicator`| Mixin style applied to indicator container, iron-selector. It can be use to specify the location of the indicator | `{}`
`--cmidt-page-indicator-space`| Space between dot indicator | `4px`
`--cmidt-page-indicator-size`| The normal size of the dot indicator | `10px`
`--cmidt-page-indicator-selected-size`| The selected size of the dot indicator | `18px`
`--cmidt-page-indicator-color`| The normal dot indicator color | `black`
`--cmidt-page-indicator-selected-color`| The color of dot indicator when it selected |#857376
`--cmidt-page-control`| Mixin style applied to control button | `{}`
`--cmidt-page-control-next`| Mixin style applied directed to next control button | `{}`
`--cmidt-page-control-previous`| Mixin style applied directed to previous control button | `{}`
`--cmidt-control-size`| The size of control button next or previous | `60px`
`--cmidt-control-color`| The color of control arrow button | `white`
`--cmidt-control-background`| The color circle background of control button | `rgba(0, 0, 0, 0.08)`
`--cmidt-control-hover-background`| The color circle background of control button when hover | `rgba(0, 0, 0, 0.5)`
@demo demo/index.html
-->
<dom-module id="cmidt-viewpager">
<template>
<style>
:host {
display: block;
overflow: hidden;
position: relative;
--iron-item-space: var(--cmidt-page-indicator-space, 4px);
--iron-normal-size: var(--cmidt-page-indicator-size, 10px);
--iron-selected-size: var(--cmidt-page-indicator-selected-size, 18px);
--iron-padding-size: calc((var(--iron-item-space) / 2) + ((var(--iron-selected-size) - var(--iron-normal-size)) / 2));
--iron-padding-selected-size: var(--iron-item-space);
--iron-item-control-size: var(--cmidt-control-size, 60px);
}
iron-scroll-threshold {
width: 100%;
height: 100%;
}
#container {
position: relative;
overflow-x: scroll;
overflow-y: hidden;
-ms-overflow-style: none;
height: calc(100% + 16px);
padding-bottom: 16px;
box-sizing: border-box;
}
#container::-webkit-scrollbar {
display: none;
}
#container > ::content > * {
margin: 0;
box-sizing: border-box;
will-change: transform;
padding-left: var(--cmidt-page-margin, 0px);
padding-right: var(--cmidt-page-margin, 0px);
@apply(--layout-fit);
@apply(--cmidt-page);
}
#container > ::content > .be-animated {
-webkit-transition: opacity 180ms, -webkit-transform 320ms; /* Safari */
transition: opacity 180ms, transform 320ms;
}
#container > ::content > .be-animated-opacity {
-webkit-transition: opacity 420ms; /* Safari */
transition: opacity 420ms;
}
:host[auto-padding] #container > ::content > * {
padding-left: calc(8px + var(--iron-item-control-size));
padding-right: calc(8px + var(--iron-item-control-size));
}
#clipping {
box-sizing: border-box;
width: 100%;
height: 100%;
}
:host[clip-padding] #clipping {
width: calc(100% - 16px - (2 * var(--iron-item-control-size)));
margin-left: calc(8px + var(--iron-item-control-size));
}
/* Indicator style */
#indicator {
color: var(--cmidt-page-indicator-color, black);
left: 50%;
bottom: 0;
transform: translate(-50%, 0);
@apply(--layout-horizontal);
@apply(--layout-center-center);
@apply(--cmidt-page-indicator);
position: absolute;
}
.indicator-item {
width: var(--iron-selected-size);
height: var(--iron-selected-size);
padding: var(--iron-padding-size);
@apply(--layout-horizontal);
@apply(--layout-center-center);
position: relative;
box-sizing:border-box;
cursor: pointer;
transition: padding 80ms ease-in-out;
}
.indicator-item.iron-selected {
padding: var(--iron-padding-selected-size);
color: var(--cmidt-page-indicator-selected-color, #857376);
}
.indicator-item iron-icon {
width: 100%;
height: 100%;
}
/* Controller */
.control {
top: 50%;
transform: translate(0, -50%);
position: absolute;
cursor: pointer;
padding: 10px;
color: var(--cmidt-control-color, white);
width: var(--iron-item-control-size);
height: var(--iron-item-control-size);
-moz-border-radius: var(--iron-item-control-size);
-webkit-border-radius: var(--iron-item-control-size);
border-radius: var(--iron-item-control-size);
background-color: var(--cmidt-control-background, rgba(0, 0, 0, 0.08));
transition: background-color 0.5s linear, visibility 0.5s linear;
@apply(--cmidt-page-control);
}
#next {
right: 0;
@apply(--cmidt-page-control-next);
}
#previous {
left: 0;
@apply(--cmidt-page-control-previous);
}
.control:hover {
background-color: var(--cmidt-control-hover-background, rgba(0, 0, 0, 0.5));
}
.control.hide {
visibility: hidden;
}
</style>
<div id="clipping">
<iron-scroll-threshold id="threshold" horizontal>
<div id="container">
<content></content>
</div>
</iron-scroll-threshold>
</div>
<!-- control -->
<paper-icon-button id="previous" class="control" on-click="_onPreviousClick" icon="cmidt-viewpager:arrow-previous" hidden$="[[hide-control]]"></paper-icon-button>
<paper-icon-button id="next" class="control" on-click="_onNextClick" icon="cmidt-viewpager:arrow-next" hidden$="[[hide-control]]"></paper-icon-button>
<!-- indicator -->
<iron-selector id="indicator" selected="{{_currentItemInternal}}" hidden$="[[hide-indicator]]">
<template is="dom-repeat" items="[[_indicatorItem]]">
<div class="indicator-item">
<iron-icon icon="cmidt-viewpager:disc"></iron-icon>
</div>
</template>
</iron-selector>
</template>
<script>
var Cmidt = Cmidt || {};
// fire when animation is done and page are in place
Cmidt.PAGE_STATE_IDLE = 0;
// fire when user start dragging the page
Cmidt.PAGE_STATE_DRAGGED = 1;
// fire when user scroll the page most likely using mouse wheel
Cmidt.PAGE_STATE_SCROLLING = 2;
// fire before animation start to move page into a proper position
Cmidt.PAGE_STATE_SETTLING = 3;
(function() {
var WHEEL_WAIT_DONE = 180;
var ANIMETION_SPEED_MULTIPLIER = 2.5;
Polymer({
/**
* Fire when new page is moving to the visible region and the old visible page
* push outside of visible region. This fire when user release the finger or scrolling
* being settle and before the animation start. Note that `page-selected` also fire if
* user tap or click on such as control button (next, previous) or the dot indicator.
* The method `setCurrentItem` is also fire the `page-selected` if `skipSelected` not specify.
*
* @event page-selected
*/
/**
* Fire when a page is detached from ViewPAger container and place under reusable list pool for later use.
* Event is attached an attach item with `event.detail`<br>
*
* 1. event.detail.item.position represent position of item related to item containr object array.<br>
* 2. event.detail.item.object represent HTML element which is attached to ViewPager container<br>
*
* @event page-detached
*/
/**
* Fire when a page is added to ViewPager container.
* Event is attached an attach item with `event.detail`
*
* 1. event.detail.item.position represent position of item related to item containr object array.<br>
* 2. event.detail.item.object represent HTML element which is attached to ViewPager container<br>
* 3. event.detail.reusable represent state of HTML element. If true, the item is takeing from reusable pool otherwise it was new item.
*
* @event page-attached
*/
/**
* Fire multiple time with different state such idle, dragged, scrolling or settling.
* Variable: `Cmidt.PAGE_STATE_IDLE`, `Cmidt.PAGE_STATE_DRAGGED`, `Cmidt.PAGE_STATE_SCROLLING`
* and `Cmidt.PAGE_STATE_SETTLING` can be use to check the state of the event.
*
* 1.`Cmidt.PAGE_STATE_IDLE` fire immediately after animation is done and page are in the exact position x or completely visible.<br>
* 2.`Cmidt.PAGE_STATE_DRAGGED` fire only one time right after user touch and drag the page to left or right.<br>
* 3.`Cmidt.PAGE_STATE_SCROLLING` fire only one time when user move the page by mouse wheel.<br>
* 4.`Cmidt.PAGE_STATE_SETTLING` fire immediately after user stop interaction such as release the finger or stop the wheel and right before animation start to settle the page coordination.
*
* @event page-state-changed
*/
/**
* Fire when the scroll read at the last page of ViewPager. This event allow the host
* applications to listen and perform lazy load content to append into ViewPager
*
* @event on-lower-threshold
*/
is: 'cmidt-viewpager',
behaviors: [
Polymer.IronScrollTargetBehavior,
Polymer.Templatizer,
Polymer.IronResizableBehavior
],
properties: {
/**
* An array containing items determining how many instances of the template as the page
* to stamp and each template instance should bind to.
*/
items: {
type: Array
},
/**
* The name of the variable to add to the binding scope for the array
* element associated with a given template instance.
*/
as: {
type: String,
value: 'item'
},
/**
* The name of the variable to add to the binding scope with the index
* for the row.
*/
indexAs: {
type: String,
value: 'index'
},
/**
* The number of invisible page on the left and the right side.
*/
pageOffset: {
type: Number,
value: 1
},
/**
* Not implement at the moment.
*/
bounce: {
type: Boolean,
value: false
},
/**
* By default, build in indicator is display at the bottom of ViewPager.
* Specify this attribute will hide the indicator.
*
* ```html
* <cmidt-viewpager hide-indicator>
* </cmidt-viewpager>
* ```
*/
hideIndicator: {
type: Boolean,
value: false,
reflectToAttribute: true,
},
/**
* By default, build in control button is display at the left and right of ViewPager.
* Specify this attribute will hide the control button.
*
* ```html
* <cmidt-viewpager hide-control>
* </cmidt-viewpager>
* ```
*/
hideControl: {
type: Boolean,
value: false,
reflectToAttribute: true,
},
/**
* The current selected item or index, base on attribute items.
* Note that to set the current item or index. Please use method setCurrentItem instead.
* Change this value will not cause the page to change it only fire the event `on-page-selected`
*/
currentItem: {
type: Number,
value: 0,
reflectToAttribute: true,
},
/**
* By default, the control button will display overlap on top of the page.
* Auto padding will set the padding left and right to the page to reserve the space
* for the control next and previous button. Also you can custom style variable such as
* `--cmidt-page` or `--cmidt-page-margin` to make space for control button as well.
* However the page still scroll behind the control button. To make page clip and not
* scroll behind the control button, please use clip-padding instead.
*
* ```html
* <cmidt-viewpager auto-padding>
* </cmidt-viewpager>
* ```
*/
autoPadding: {
type: Boolean,
value: false,
reflectToAttribute: true,
},
/**
* Clip Padding will clip the page to the available space between control button next and previous.
* The page will not scroll behind button control and the content will clip at the edge left and right.
* This must not be use together with auto-padding.
*
* ```html
* <cmidt-viewpager clip-padding>
* </cmidt-viewpager>
* ```
*/
clipPadding: {
type: Boolean,
value: false,
reflectToAttribute: true
},
/**
* State represent whether or not ViewPager should fire event such on detached or attached and other event.
*/
enableExtraEvent: {
type: Boolean,
value: false,
reflectToAttribute: true
},
/**
* The current internal selected item. Use to bind value between iron-selector and view pager.
*/
_currentItemInternal: {
type: Number,
value: 0
},
/**
* The binding object for indicator.
*/
_indicatorItem: {
type: Array
}
},
/**
* ViewPager height
*/
_viewportHeight: 0,
/**
* ViewPager width
*/
_viewportWidth: 0,
/**
* Total scrollable width
*/
_scrollableWidth: 0,
/**
* Current scroll left position
*/
_scrollPosition: 0,
/**
* Current scrolling direction
*/
_scrollDirection: 0,
/**
* Touch drag start scroll left position. Use to track left scroll while tracking
*/
_touchDragScrollPosition: 0,
/**
* A maximum offset of scroll movement to determin new page need to populate into container
*/
_populateOffset: 0,
/**
* A state to determin if ViewPager currently populated the items
*/
_isPopulating: false,
/**
* A minimum distance of scroll movement to determin final scroll left position before animated.
*/
_nextPositionOffset: 0,
/**
* A ViewPager state, See Cmidt.PAGE_STATE_IDLE, Cmidt.PAGE_STATE_DRAGGED ...etc
*/
_state: 0,
/**
* A list of current attached element into container. Represent in the form:
*
* {
* position: // position of item related to real position in array items containing object
* object: // HTML element that attached to container
* scrolling: // true/false determin if the item is current scrolling
* template: // true/false determin if the item was create from template or manually from content
* }
*
*/
_attachedItems: null,
/**
* A list of current detached element from container. Represent in the object the same as _attachedItems above.
* This used to store detached element so that it can be re-use to bind with other containing object and re-attached
* back to the container.
*/
_reusableItems: null,
/**
* Size of dot indicator
*/
_indicatorSize: 0,
/**
* State to determin whether or not user is current interact with pager by touch
*/
_isTouched: false,
/**
* State used to detect transition css transition of child when removed. To prevent any action
* to change the page. It's represent in form of object
*/
_removeTransitions: null,
/**
* State to determin if page current scrolling to take place
*/
_isAnimated: false,
/**
* A long number to track the async schedule for mouse wheel scrolling finish
*/
_scrollFinishedHandler: null,
/**
* A state to indicate that the wheel should be cancel and no long need.
* TODO: when implement bounce this will be useful
*/
_shouldStopWheelPropagation: false,
/**
* A long number ot track the async schedule for animation loop. Use to finish or cancel if user
* interact with ViewPager while animation is going on
*/
_animationFrameRequestID: null,
/**
* State to determin if we should take track event to move page when user touch and move. Normally
* It's always true except when user move vertically as the page content might overflow and need to
* be scroll up/down.
*/
_isBeingDragged: true,
/**
* A float number use to track the total distance of track move by the user
*/
_lastDelta: 0,
/**
* A start use to track user start moving page. Use to determin velocity
*/
_startTrackTime: 0,
/**
* A state to check whether a scrolling from mouse wheel is fired. The event will fire immediately after scroll start
* as we need to make sure that user scroll horizontally and not vertical
*/
_hasFireScrolling: false,
/**
* A state to determin whether should fire page selection event when a current position of the item change
*/
_shouldFireSelectedEvent: false,
/**
* This use to determin whether template has provided. (Should remove this and use this.ctor instead.)
*/
_hasTemplate: false,
observers: [
'_onItemsChanged(items.*)',
'_onCurrentItemChanged(currentItem)',
'_onCurrentItemInternalChanged(_currentItemInternal)',
'_onHideControlChanged(hideControl)',
'_onHideIndicatorChanged(hideIndicator)'
],
listeners: {
'touchmove': '_onTouchMove',
'touchstart': '_onTouchStart',
'touchend': '_onTouchEnd',
// 'wheel': '_onMouseWheel',
// track will be toggle when touch start or touch end to avoid click move on desktop browser
// 'track': '_onTrack',
'down': '_onDown',
'up': '_onUp',
'transitionend': '_onCssTransitionEnd',
'iron-resize': '_onResizeHandler'
},
ready: function() {
this.scrollTarget = this.$.container;
this.$.threshold.scrollTarget = this.$.container;
},
attached: function() {
this.updateViewportBoundaries();
if (this._viewportWidth == 0) {
// fixed problem with certain case where this.offsetWidth is return 0
// where a bit delay will provide the size.
if (this.items && this.items.length > 0){
this.async(function() {
this.attached();
}, 50);
}
return;
}
if(this.items && this.items.length > 0) {
this._populate();
this._populateIndicator();
} else if (this.$.container.children.length > 0) {
var child = this.$.container.children;
this._indicatorItem = [];
this._attachedItems = this._attachedItems || [];
for(var i = 0; i < child.length; i++) {
if (child[i].localName != "template") {
var item = {};
item.position = i;
item.object = child[i];
item.scrolling = false;
item.template = false;
this._attachedItems.push(item);
this.push('_indicatorItem', i);
this.translate3d((i * this._viewportWidth) + 'px', 0, 0, item.object);
}
}
}
},
_forwardInstanceProp: function(inst, prop, value){
// TODO: custom forward
},
_forwardInstancePath: function(inst, path, value) {
// TODO: custom forward
},
_forwardParentProp: function(prop, value) {
// TODO: what we do here
},
_forwardParentPath: function(path, value) {
// TODO: impelement path forward
},
/**
* Called as a side effect of a host items.<key>.<path> path change,
* responsible for notifying item.<path> changes.
*/
_forwardItemPath: function(path, value) {
var dot = path.indexOf('.');
var key = path.substring(1, dot < 0 ? path.length : dot);
var item = null;
for (var i = 0; i < this._attachedItems.length; i++) {
if (this._attachedItems[i].position == key) {
item = this._attachedItems[i];
break;
}
}
// no item visible found ignore. the reusable binding will take the change later on
if (!item){
return;
}
if (dot >= 0) {
path = this.as + '.' + path.substring(dot+1);
item.object._templateInstance.notifyPath(path, value, true);
} else {
item.object._templateInstance[this.as] = value;
}
},
get _isVisible() {
return Boolean(this.offsetWidth || this.offsetHeight);
},
_onItemsChanged: function(change) {
this.updateViewportBoundaries();
if (change.path === 'items') {
this._physicalIndexForKey = {};
this._attachedItems = this._attachedItems || [];
this._reusableItems = this._reusableItems || [];
// this mean a complete change to the entire items containing object.
// reset scroll, current item and rebind
if (this.currentItem != 0){
this.currentItem = 0;
this._currentItemInternal = 0;
} else {
// explicitly fire page-selected as the currentItem is 0 no change is being trigger.
// fire this so that the host can use to change accordingly such as custom indicator ...etc
this._onCurrentItemChanged();
}
if (this._scrollLeft != 0){
// 0, animate = false, fireState = true
this._scrollPageTo(0, false, false);
}
//
this.$.container.style['overflow-x'] = 'hidden';
this._populate(true);
this._populateIndicator();
this.toggleClass('hide', this.currentItem == 0, this.$.previous);
this.toggleClass('hide', this.currentItem == this.items.length - 1, this.$.next);
this.$.container.style['overflow-x'] = 'scroll';
} else if (change.path === 'items.splices') {
if (this._viewportWidth != 0 && this._viewportHeight != 0){
var changeInfo = change.value.indexSplices[0];
var rePopulate = false;
if (changeInfo.removed && changeInfo.removed.length > 0){
if (this._needRemoveAnimation(changeInfo)){
// remove animation take place first
return;
} else if (changeInfo.index < this.currentItem) {
this._setCurrentItemInternal(this.currentItem - changeInfo.removed.length, true, true);
this._invalideAttachedContent();
rePopulate = true;
} else if ((this.currentItem + this.pageOffset) <= changeInfo.index) {
rePopulate = true;
}
} else if (changeInfo.addedCount > 0) {
if (this._needAddAnimation(changeInfo)) {
// make space animation take place first
return;
} else if (changeInfo.index <= (this.currentItem + this.pageOffset)) {
if (changeInfo.index < this.currentItem){
this._setCurrentItemInternal(this.currentItem + changeInfo.addedCount, true, true);
this._invalideAttachedContent();
}
rePopulate = true;
}
}
this._rePopulateItemOnSplice(rePopulate, !rePopulate);
}
} else {
this._forwardItemPath(change.path.split('.').slice(1).join('.'), change.value);
}
},
_needRemoveAnimation: function(changeInfo) {
if (this.items.length == 0) {
// no need to compute any more. all item is remove.
var index = this._getVisibleAttachedItem();
if (index != -1) {
var item = this._attachedItems[index];
this.toggleClass('be-animated', true, item.object);
item.object.style.opacity = 0;
this.translate3d((this.currentItem * this._viewportWidth)+'px', this._viewportHeight+'px', 0, item.object);
}
this._removeTransitions = {
// assign moveIn as fake pointing to item as no more item and transition end required moveIn to process forward.
moveIn: item,
moveOut: item,
removedSize: changeInfo.removed.length
};
return true;
}
if (changeInfo.index == this.currentItem ||
(this.currentItem < changeInfo.index + changeInfo.removed.length)) {
var index = this._getVisibleAttachedItem();
if (index != -1) {
var inItem;
var fromRight;
var item = this._attachedItems[index];
if (changeInfo.index >= this.items.length) {
// we reach the right side. we should animate item in from the left side.
fromRight = false;
inItem = this._attachedItems[index-1];
} else {
fromRight = true;
inItem = this._attachedItems[index+1];
}
// populate item in before animate
var rebindIndex;
if (fromRight) {
rebindIndex = changeInfo.index;
this._rebindReusableItem(inItem, inItem.object._templateInstance, changeInfo.index);
} else {
rebindIndex = changeInfo.index - 1;
this._rebindReusableItem(inItem, inItem.object._templateInstance, rebindIndex);
}
this.toggleClass('be-animated', true, item.object);
this.toggleClass('be-animated', true, inItem.object);
item.object.style.opacity = 0;
this.translate3d((this.currentItem * this._viewportWidth)+'px', this._viewportHeight+'px', 0, item.object);
this.translate3d((this.currentItem * this._viewportWidth)+'px', 0, 0, inItem.object);
this._removeTransitions = {
moveIn: inItem,
moveOut: item,
rebindIndex: rebindIndex,
removedSize: changeInfo.removed.length
};
}
return true;
}
return false;
},
_needAddAnimation: function(changeInfo) {
if (this.currentItem == changeInfo.index) {
var index = this._getVisibleAttachedItem();
if (index == -1 && this._attachedItems.length == 0) {
this._addNewItem(0, -1);
index = 0;
}
var item = this._attachedItems[index];
var inItem = index == this._attachedItems.length - 1 ? this._attachedItems[index - 1] : this._attachedItems[index + 1];
if (!inItem && this.items.length == 2 && this._attachedItems.length == 1) {
// no spare item for animation
this._addNewItem(this.currentItem + 1, -1);
inItem = this._attachedItems[1];
} else if (this.items.length == 1) {
inItem = item;
}
this._rebindReusableItem(inItem, inItem.object._templateInstance, this.currentItem);
inItem.object.style.opacity = 0;
this.translate3d((this.currentItem * this._viewportWidth)+'px', 0, 0, inItem.object);
if (inItem != item) {
this.toggleClass('be-animated', true, item.object);
this.translate3d(((this.currentItem + 1) * this._viewportWidth)+'px', 0, 0, item.object);
}
this.async(function(){
this.toggleClass('be-animated-opacity', true, inItem.object);
inItem.object.style.opacity = 1;
}, 120);
this._removeTransitions = {
moveIn: inItem,
moveOut: item,
rebindIndex: this.currentItem,
addedSize: changeInfo.addedCount
};
return true;
}
return false;
},
_rePopulateItemOnSplice: function(rebind, onlyIndicator) {
if (!onlyIndicator) {
// scroll should not have animation but should fire selection change
this._populate(rebind);
// explicitly fire page-selected as the currentItem has no change and observer will not fire.
// fire this so that the host can use to change accordingly such as custom indicator ...etc
// TODO: need it ? not sure as we change index early before re-populate so observer should has been fired
this._onCurrentItemChanged();
}
this._populateIndicator();
this.toggleClass('hide', this.currentItem == 0, this.$.previous);
this.toggleClass('hide', this.currentItem == this.items.length - 1, this.$.next);
},
_invalideAttachedContent: function() {
var item;
for (var i = 0; i < this._attachedItems.length; i++) {
item = this._attachedItems[i];
item.position = -1;
}
},
_getVisibleAttachedItem: function() {
for (var i = 0; i < this._attachedItems.length; i++) {
if (this._attachedItems[i].position == this.currentItem) {
return i;
}
}
return -1;
},
_onCurrentItemChanged: function(change) {
if (this._shouldFireSelectedEvent) {
this.fire('page-selected', {position: this.currentItem});
}
// setCurrentItem can avoid callback but not for other
this._shouldFireSelectedEvent = true;
},
_onCurrentItemInternalChanged: function(change) {
if (this._currentItemInternal != this.currentItem){
this._setCurrentItemInternal(this._currentItemInternal);
}
},
_onHideControlChanged: function(){
this.$.next.hidden = this.hideControl;
this.$.previous.hidden = this.hideControl;
},
_onHideIndicatorChanged: function() {
this.$.indicator.hidden = this.hideIndicator;
},
_ensureTemplatized: function() {
if (!this.ctor) {
// According to https://www.polymer-project.org/1.0/docs/api/Polymer.Templatizer
// custom forward required _instanceProps
var props = {};
props[this.as] = true;
props[this.indexAs] = true;
this._instanceProps = props;
this._userTemplate = Polymer.dom(this).querySelector('template');
if (this._userTemplate) {
this.templatize(this._userTemplate);
this._hasTemplate = true;
} else {
console.warn('cmidt-viewpager requires a template to be provided in light-dom');
return false;
}
}
return true;
},
_onPreviousClick: function() {
this._setCurrentItemInternal(this.currentItem - 1);
},
_onNextClick: function() {
this._setCurrentItemInternal(this.currentItem + 1);
},
_onTouchMove: function(event) {
if (this._isBeingDragged) {
event.preventDefault();
}
},
_onTouchStart: function(event) {
this._isBeingDragged = true;
this.listen(this, 'track', '_onTrack');
this.$.container.style['overflow-x'] = 'hidden';
},
_onTouchEnd: function(event) {
this.unlisten(this, 'track', '_onTrack');
this.$.container.style['overflow-x'] = 'scroll';
},
_onTrack: function(event) {
if (this._removeTransitions) {
return;
}
switch(event.detail.state) {
case 'start':
this._startTrackTime = Date.now();
this._touchDragScrollPosition = this._scrollLeft;
break;
case 'track':
if (this._isBeingDragged && this._isTrackUnderViewPager(event.detail.hover())) {
var dx = Math.abs(event.detail.dx);
var dy = Math.abs(event.detail.dy);
if (dy > 20 && dy > dx) {
this._isBeingDragged = false;
this.unlisten(this, 'track', '_onTrack');
return
}
if (!this._hasBeenFireDragged) {
this._hasBeenFireDragged = true;
this.fire('page-state-changed', {state: Cmidt.PAGE_STATE_DRAGGED});
this._state = Cmidt.PAGE_STATE_DRAGGED;
}
this._lastDelta = event.detail.dx;
this._move(this._lastDelta);
event.stopPropagation();
event.preventDefault();
}
break;
case 'end':
if (this._isBeingDragged) {
var deltaTime = Date.now() - this._startTrackTime;
var velocity = this._lastDelta / deltaTime;
this._settleViewPosition(velocity);
}
this._hasBeenFireDragged = null;
this._isBeingDragged = true;
this._touchDragScrollPosition = 0;
break;
}
},
_onDown: function(event) {
var localName = event.target.localName;
if (localName != 'paper-icon-button' && localName != 'iron-icon'){