我想知道是否有可能禁用多选下拉菜单中存在的某些复选框项。多选有一个选项，以禁用整个下拉菜单，但我想知道，如果我们可以禁用特定的复选框。对于下面的代码，是否有办法禁用默认选中的复选框值。
TS
import { Component, OnInit } from '@angular/core';
export class AppComponent implements OnInit {
dropdownList = [];
selectedItems = [];
dropdownSettings = {};
ngOnInit(){
this.dropdownList = [
{"id":1,"itemName":"India"},
{"id":2,"itemName":"Singapore"},
{"id":3,"itemName":"Australia"},
{"id":4,"itemName":"Canada"},
{"id":5,"itemName":"South Korea"},
{"id":6,"itemName":"Germany"},
{"id":7,"itemName":"France"},
{"id":8,"itemName":"Russia"},
{"id":9,"itemName":"Italy"},
{"id":10,"itemName":"Sweden"}
];
this.selectedItems = [
{"id":2,"itemName":"Singapore"},
{"id":3,"itemName":"Australia"},
{"id":4,"itemName":"Canada"},
{"id":5,"itemName":"South Korea"}
];
this.dropdownSettings = {
singleSelection: false,
text:"Select Countries",
selectAllText:'Select All',
unSelectAllText:'UnSelect All',
enableSearchFilter: true,
classes:"myclass custom-class"
};
}
onItemSelect(item:any){
console.log(item);
console.log(this.selectedItems);
}
OnItemDeSelect(item:any){
console.log(item);
console.log(this.selectedItems);
}
onSelectAll(items: any){
console.log(items);
}
onDeSelectAll(items: any){
console.log(items);
}
}