問題是你正在做功能綁定與[expanded]
。所以,每次檢測運行時,都會一次又一次地檢測shouldBeExpanded
函數。
選項1:
如果你想使用shouldBeExpanded
爲[擴展]標誌保留,您可以使用OnPush
變化檢測策略。
當我測試這個時,擴展和崩潰是一點點的毛病。嘗試一下在演示
TS:
import {Component, ChangeDetectionStrategy} from '@angular/core';
import {Http} from '@angular/http'
import {bootstrap} from '@angular/platform-browser-dynamic';
import 'rxjs/add/operator/map'
@Component({
selector: 'material-app',
templateUrl: 'app.component.html',
changeDetection: ChangeDetectionStrategy.OnPush
})
Plunker demo
選項2:
而不是與功能結合,可以創建,保持軌道的數組每個擴展標誌。您可以使用OnInit
初始化陣列,並將值存儲在localstorage
中。如果值不在本地存儲中,則可以分配默認標誌。每當擴展狀態發生變化時,都要在數組中更新並且localstorage
。
TS:
export class AppComponent implements OnInt {
private version: any;
items = ["a1", "a2", "a3"];
expansionFlag = [];
constructor(http: Http) {
// Display the currently used Material 2 version.
this.version = http
.get('https://api.github.com/repos/angular/material2-builds/commits/HEAD')
.map(res => res.json())
}
ngOnInit(){
for(let i = 0; i <this.items.length; i++){
let flag = JSON.parse(localStorage.getItem(this.items[i]));
console.log(flag);
if(flag != undefined && flag != null){
this.expansionFlag.push(flag);
}
else
this.expansionFlag.push(false);
}
console.log(this.expansionFlag)
}
openPanel(name, index) {
console.log(name, 'is now open')
this.expansionFlag[index] = true;
localStorage.setItem(name, 'true');
}
closePanel(name, index) {
console.log(name, 'is now closed');
this.expansionFlag[index] = false;
localStorage.setItem(name, 'false');
}
}
更新在HTML中,每[expanded]
:
[expanded]="expansionFlag[0]"
[expanded]="expansionFlag[1]"
[expanded]="expansionFlag[2]"
Plunker demo