md-autocomplete onSelectionChange两次触发

Question

我angular/material: 2.0.0-beta.5在Angular应用程序中使用md-autocomplete .随着最新版本的发布,该selected方法已被替换onSelectionChange.

第一次选择下拉列表中的值时,关联的方法仅触发一次,但如果我从下拉列表中选择一个新值,则会选择两次(第二次具有前一个值).

逻辑与以前的版本一起正常工作.

模板

<md-autocomplete #panel="mdAutocomplete" [displayWith]="displayFn">
   <md-option (onSelectionChange)="selected(country)" *ngFor="let country of filteredCountries | async" [value]="country">
    <div class="selector-elements">
      <span>
          <img [src]="getFlagPath(country.code)" [width]="24" [height]="24" /> 
      </span>    {{ country.name }}
      </div>
</md-option>

调节器

export class CountrySelector implements OnInit, ControlValueAccessor {

// ...

initCountries() {
    this.countryList = countryNames;

    this.filteredCountries = this.formControlName.valueChanges
        .startWith(null)  //-> OnInit the countries are filtered by null, hence all results are returned.
        .map(country => {
            return country && typeof country === 'object' ? country.name : country
        })
        .map(name => name ? this.filter(name) : this.countryList.slice());
}

filter(val: string): ICountry[] {
    //Regex to match with the first letters of the country name with the passed value.
    return this.countryList.filter(country => new RegExp(`^${val}`, 'gi').test(country.name));
}

resetCountrySelection(){
    let country = new Country();
    this.formControlName.setValue(country);
    this.propagateChange(country);
}

writeValue(country: Country): void {
    if (country) {
        this.formControlName.setValue(country);
    }
}

selected(country: ICountry) {
   // Here it gets triggered twice when a new element is chosen
   this.propagateChange(country);
}

propagateChange = (_: any) => { };

registerOnChange(fn: any) {
    this.propagateChange = fn;
}

}

Answer 1

发生的事情是onSelectionChange按顺序触发新选中和未选中的选中.如果您将$ event添加到您的通话中

(onSelectionChange)="selected($event, country)"

然后,您可以通过查看此类源来检查它是否是所选的

selected(event: MdOptionSelectionChange, country: ICountry) {
   if (event.source.selected) {
       this.propagateChange(country);
   }
}