我在Angular应用程序中使用md-autocomplete angular/material: 2.0.0-beta.5
。在最新版本中,selected
方法已被onSelectionChange
取代。
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)。
逻辑与之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>
控制器
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(`^${val}`, 'gi').test(country.name));
}
resetCountrySelection(){
let country = new Country();
this.formControlName.setValue(country);
this.propagateChange(country);
}
writeValue(country: Country): void {
if (country) {
this.formControlName.setValue(country);
}
}
selected(country: ICountry) {
// Here it gets triggered twice when a new element is chosen
this.propagateChange(country);
}
propagateChange = (_: any) => { };
registerOnChange(fn: any) {
this.propagateChange = fn;
}
}
答案 0 :(得分:14)
正在发生的事情是onSelectionChange按顺序触发新选中的和未选中的选中。如果您将$ event添加到您的通话中
(onSelectionChange)="selected($event, country)"
然后你可以通过查看这样的来源来检查它是否是所选的
selected(event: MdOptionSelectionChange, country: ICountry) {
if (event.source.selected) {
this.propagateChange(country);
}
}