[英]How to change the dropdown value based on click of Previous/Next button in angular8
[英]How to change the dropdown value, if we have more records without having break using angular8
我在我的项目中使用了 Angular8,如果我有 2-3 条记录,那么上一个和下一个工作正常,但是如果我有更多记录,那么当我单击上一个/下一个时,它会破坏代码并击中中间。 任何人都可以帮忙,如何解决这个问题。 我附上了我的代码的工作演示。
TS:
public changeDropdown(value) {
const entry = this.dropdownValue.findIndex(x => x.noteId === parseInt(value));
this.selectedDropdownValue = this.dropdownValue[entry].noteId;
}
public previousNextValue(value) {
let previousValue = this.selectedDropdownValue;
previousValue = value ? ++previousValue : --previousValue;
this.changeDropdown(previousValue);
}
HTML:
<div class="card-footer text-right">
<button class="btn btn-outline-primary" type="button" (click)="previousNextValue(false)"
[disabled]="selectedDropdownValue<=1"><i class="fas fa-chevron-left"></i>
Previous</button>
<button class="btn btn-outline-primary ml-1" type="button" (click)="previousNextValue(true)"
[disabled]="selectedDropdownValue==dropdownValue.length">Next <i class="fas fa-chevron-right"></i></button>
</div>
问题是您正在寻找一个不存在的 ID,并且您使用相同的变量作为值和索引,这会造成麻烦,您必须创建另一个变量来设置 previousValue。 这是一个例子。
selectedDropdownValue:number = 0;
globalPreviousValue: number = 0;
public dropdownValue = [
{"noteId":1,"noteTypeId":1,"noteTypeName":null,"noteSubject":"subject -1","createdDate":"2020-08-07T15:21:48.71","createdBy":"Admin","noteText":null,"dropdownSubject":"08/07/2020 Admin subject -1"},{"noteId":2,"noteTypeId":2,"noteTypeName":null,"noteSubject":"subject -2 test","createdDate":"2020-08-07T15:25:38.553","createdBy":"Admin","noteText":null,"dropdownSubject":"08/07/2020 Admin subject -2 test"},{"noteId":3,"noteTypeId":2,"noteTypeName":null,"noteSubject":"subject -3 test","createdDate":"2020-08-11T11:26:36.007","createdBy":"Admin","noteText":null,"dropdownSubject":"08/11/2020 Admin subject -3 test"},{"noteId":10,"noteTypeId":3,"noteTypeName":null,"noteSubject":"test","createdDate":"2020-08-12T11:50:14.653","createdBy":"Admin","noteText":null,"dropdownSubject":"08/12/2020 Admin test"},{"noteId":11,"noteTypeId":5,"noteTypeName":null,"noteSubject":"tested","createdDate":"2020-08-12T14:36:43.41","createdBy":"Admin","noteText":null,"dropdownSubject":"08/12/2020 Admin tested"},
{"noteId":12,"noteTypeId":135,"noteTypeName":"Email sent to Agent","noteSubject":"test","createdDate":"2020-08-12T17:25:15.71","createdBy":"Admin","noteText":null,"dropdownSubject":"08/12/2020 Admin test"},
{"noteId":13,"noteTypeId":136,"noteTypeName":"Fax to Agent","noteSubject":"tested","createdDate":"2020-08-12T17:29:59.97","createdBy":"Admin","noteText":null,"dropdownSubject":"08/12/2020 Admin tested"}]
public changeDropdown(value) {
this.globalPreviousValue = value
this.selectedDropdownValue = this.dropdownValue[value].noteId;
}
public previousNextValue(value) {
let previousValue = this.globalPreviousValue;
previousValue = value ? ++previousValue : --previousValue;
this.changeDropdown(previousValue);
}
还要更改 HTML 中的验证,以便按需要工作。
<div class="card-footer text-right">
<button class="btn btn-outline-primary" type="button" (click)="previousNextValue(false)"
[disabled]="globalPreviousValue<=1"><i class="fas fa-chevron-left"></i>
Previous</button>
<button class="btn btn-outline-primary ml-1" type="button" (click)="previousNextValue(true)"
[disabled]="globalPreviousValue==dropdownValue.length-1">Next <i class="fas fa-chevron-right"></i></button>
</div>
您需要将逻辑从值重构为数组的索引,例如
export class AppComponent {
selectedDropdownValue:number = 0;
selectedIndex: number = -1;
public dropdownValue = []; // data
public previousNextValue(selectedIndex) {
this.selectedIndex = selectedIndex;
this.selectedDropdownValue = this.dropdownValue[selectedIndex].noteId;
}
public changeDropdown(selectedDropdownValue){
this.selectedDropdownValue = selectedDropdownValue;
this.selectedIndex = this.dropdownValue.findIndex(x => x.noteId === parseInt(selectedDropdownValue));
}
}
你对下一个和上一个的看法就像
<select class="custom-select w-100" name="noteTypeId" (change)="changeDropdown($event.target.value)" [value]="selectedDropdownValue">
<option value="0" selected disabled>Select Note Details</option>
<option *ngFor="let notesItem of dropdownValue" [value]="notesItem.noteId">
{{notesItem.dropdownSubject}}
</option>
</select>
<div class="card-footer text-right">
<button class="btn btn-outline-primary" type="button" (click)="previousNextValue(selectedIndex - 1)"
[disabled]="selectedIndex < 1"><i class="fas fa-chevron-left"></i>
Previous</button>
<button class="btn btn-outline-primary ml-1" type="button" (click)="previousNextValue(selectedIndex + 1)"
[disabled]="selectedIndex >= dropdownValue.length - 1">Next <i class="fas fa-chevron-right"></i></button>
</div>
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