Ionic slides - dynamically add slides before and after

Question

Hi I'm using ngFor to create an set of 3 slides while starting in the middle so I'm guaranteed to be able to slide to left or right on start.

When I slide right I can simple listen to the reachedEnd and push another slide to the array i'm looping.

but I have a problem with adding a slide to the beginning. If I do the same as above and use e.g. array.unshift() or spread to add an item to the beginning, the view think it's on position 0 and snaps the view to the new slide.

The code below would work but it animates the slide change back to index 1.

slide = [0,1,2] //example to loop
slideChanged(event) {
    if(this.slides.isBeginning()){
        this.slide = [this.slide[0]-1, ...this.slide];
        this.slides.update();
        this.slides.slideTo(1)
    }
}

<ion-slides [initialSlide]="1" (ionSlideDidChange)="slideChanged($event)">
    <ion-slide *ngFor="let item of slide">
        <h1>Slide {{item}}</h1>
    </ion-slide>
</ion-slides>

Any help is appreciated!

Answer 1

You can do that by using the ionSlideNextEnd and ionSlidePrevEnd events from the Slides. Please take a look at this working plunker

The view

<ion-header>
  <ion-navbar>
    <ion-title>Dynamic slides Demo</ion-title>
  </ion-navbar>
</ion-header>
<ion-content>
    <ion-slides #slider (ionSlideNextEnd)="loadNext()" (ionSlidePrevEnd)="loadPrev()" [initialSlide]="1">
        <ion-slide *ngFor="let n of numbers">
            <h2>Current slide: {{n}}</h2>
        </ion-slide>
    </ion-slides>
</ion-content>

The component

@Component({...})
export class HomePage {
    @ViewChild('slider') private slider: Slides;

    numbers = [0,1,2];
    firstLoad = true;

    constructor() {}

    loadPrev() {
        console.log('Prev');
        let newIndex = this.slider.getActiveIndex();

        newIndex++;
        this.numbers.unshift(this.numbers[0] - 1);
        this.numbers.pop();

        // Workaround to make it work: breaks the animation
        this.slider.slideTo(newIndex, 0, false);

        console.log(`New status: ${this.numbers}`);
    }

    loadNext() {
        if(this.firstLoad) {
          // Since the initial slide is 1, prevent the first 
          // movement to modify the slides
          this.firstLoad = false;
          return;
        }

        console.log('Next');
        let newIndex = this.slider.getActiveIndex();

        newIndex--;
        this.numbers.push(this.numbers[this.numbers.length - 1] + 1);
        this.numbers.shift();

        // Workaround to make it work: breaks the animation
        this.slider.slideTo(newIndex, 0, false);

        console.log(`New status: ${this.numbers}`);
    }
}

Answer 2

For you who wonder why this not works on Ionic 4, just add little bit changes on typescript component

This code below works on IONIC 4 :

ionSlideNextEnd(){
  if(this.firstLoad) {
    // Since the initial slide is 1, prevent the first 
    // movement to modify the slides
    this.firstLoad = false;
    return;
  }

  console.log('Next');
  this.daySlider.getActiveIndex().then(idx=>{
      let newIndex=idx
      console.log(newIndex)
      newIndex--;
      this.numbers.push(this.numbers[this.numbers.length - 1] + 1);
      this.numbers.shift();

      // Workaround to make it work: breaks the animation
      this.daySlider.slideTo(newIndex, 0, false);

      console.log(`New status: ${this.numbers}`);
  });


}

ionSlidePrevEnd(){
console.log('Prev');
this.daySlider.getActiveIndex().then(idx=>{
    let newIndex=idx
    console.log(newIndex)
    newIndex++;
    this.numbers.unshift(this.numbers[0] - 1);
    this.numbers.pop();

    // Workaround to make it work: breaks the animation
    this.daySlider.slideTo(newIndex, 0, false);

    console.log(`New status: ${this.numbers}`);
});
}

Or Much more simpler you can remove getter for Active Index, use below code for Ionic 4:

ionSlideNextEnd(){
    if(this.firstLoad) {
        this.firstLoad = false;
        return;
    }else{
        this.numbers.push(this.numbers[this.numbers.length - 1] + 1);
        this.numbers.shift();

        // Workaround to make it work: breaks the animation
        this.daySlider.slideTo(1,0,false);
        this.monthViewData.selectedTime=new Date(this.monthViewData.selectedTime.setDate(this.monthViewData.selectedTime.getDate()+1));
        this.eventSource = this.tmp_events.filter((item)=>{
            if(item.startTime >= this.monthViewData.selectedTime.setHours(0,0,0,0) && item.endTime < this.monthViewData.selectedTime.getTime()){
                return item;
            }
        });
    }

}

ionSlidePrevEnd(){

    this.numbers.unshift(this.numbers[0] - 1);
    this.numbers.pop();

    this.daySlider.slideTo(1,0,false);
    this.monthViewData.selectedTime=new Date(this.monthViewData.selectedTime.setDate(this.monthViewData.selectedTime.getDate()-1));
    this.eventSource = this.tmp_events.filter((item)=>{
        if(item.startTime >= this.monthViewData.selectedTime.setHours(0,0,0,0) && item.endTime <= this.monthViewData.selectedTime.getTime()){
            return item;
        }
    });
}