Question

当我们通过箭头键进入选项并按空格键（32）选择mat-chip时如何填充onkeypress(spacebar) mat-option。

但是，当我们选择选择下拉菜单时，可以通过箭头键进入选项，然后按Enter键（键码13），但不能在空格键（键码-32）上进行类似操作，效果很好。

在这里，是stackblitz链接：- https://stackblitz.com/edit/angular-ytk8qk-feaqaw?file=app/chips-autocomplete-example.html

1) How to add select dropdown option by going through
  arrowkey(not mouse) and populating selected option using spacebar(keycode- 32).

2)How to remove option from dropdown that is already populated or used.

3)Show dropdown only when user enters some charcter in input text else show 
  class="info"` text only in dropdown, when no input text is there and no 
 option in dropdown matches enter charcters in input.

Note:- The user can create chips by typing in input and then press ENTER or SPACE key (separator key) for creating chips.

chip.component.ts

export class ChipsAutocompleteExample {
  visible = true;
  selectable = true;
  removable = true;
  addOnBlur = true;
  separatorKeysCodes: number[] = [ENTER,SPACE, COMMA];
  fruitCtrl = new FormControl();
  filteredFruits: Observable<string[]>;
  fruits: string[] = ['Lemon'];
  allFruits: string[] = ['Apple', 'Lemon', 'Lime', 'Orange', 'Strawberry'];

  @ViewChild('fruitInput') fruitInput: ElementRef<HTMLInputElement>;
  @ViewChild('auto') matAutocomplete: MatAutocomplete;

  constructor() {
    this.filteredFruits = this.fruitCtrl.valueChanges.pipe(
        startWith(null),
        map((fruit: string | null) => fruit ? this._filter(fruit) : this.allFruits.slice()));
  }

  add(event: MatChipInputEvent): void {
    // Add fruit only when MatAutocomplete is not open
    // To make sure this does not conflict with OptionSelected Event
    if (!this.matAutocomplete.isOpen) {
      const input = event.input;
      const value = event.value;

      // Add our fruit
      if ((value || '').trim()) {
        this.fruits.push(value.trim());
      }

      // Reset the input value
      if (input) {
        input.value = '';
      }

      this.fruitCtrl.setValue(null);
    }
  }

  remove(fruit: string): void {
    const index = this.fruits.indexOf(fruit);

    if (index >= 0) {
      this.fruits.splice(index, 1);
    }
  }

  selected(event: MatAutocompleteSelectedEvent): void {
    this.fruits.push(event.option.viewValue);
    this.fruitInput.nativeElement.value = '';
    this.fruitCtrl.setValue(null);
  }

  private _filter(value: string): string[] {
    const filterValue = value.toLowerCase();

    return this.allFruits.filter(fruit => fruit.toLowerCase().indexOf(filterValue) === 0);
  }
}

Answer 1

1）如何通过执行添加选择下拉选项箭头键（不是鼠标），并使用空格键（键码32）填充选定的选项。

添加属性以保存选定的水果和当前显示的水果（已过滤的水果）：

selectedFruit = -1; displayedFruits = [];
在查看初始化之后，订阅keyManager上的更改以获取所选选项，并订阅已过滤水果的更改以获取已过滤列表并将其存储在displayFruits上：

ngAfterViewInit() { this.matAutocomplete._keyManager.change.subscribe((index) => { if (index >= 0) { this.selectedFruit = index; } }) this.filteredFruits.subscribe((filteredFruits) => { this.displayedFruits = filteredFruits; }); }
在add方法上，包含一个else子句以包含水果，并将selectedFruit重置为-1：

add(event: MatChipInputEvent): void { // Add fruit only when MatAutocomplete is not open // To make sure this does not conflict with OptionSelected Event if (!this.matAutocomplete.isOpen) { // ... } else { if (this.selectedFruit >= 0) { this.fruits.push(this.displayedFruits[this.selectedFruit]) this.fruitInput.nativeElement.value = ''; this.fruitCtrl.setValue(null); } else if (this.fruitInput.nativeElement.value !== '' && this.displayedFruits.length === 0) { this.fruits.push(this.fruitInput.nativeElement.value) this.fruitInput.nativeElement.value = ''; this.fruitCtrl.setValue(null); } } this.selectedFruit = -1; }

2）如何从已填充或已使用的下拉菜单中删除选项。

增强过滤器以检查是否已经使用过的水果：

private _filter(value: string): string[] {
  const filterValue = value.toLowerCase();

  return this.allFruits.filter(fruit => fruit.toLowerCase().indexOf(filterValue) === 0 && !this.fruits.find( existingFruit => existingFruit === fruit ));
}

3）仅在用户在输入文本中输入字符时显示下拉菜单，否则显示当没有输入文本且没有输入文本时，仅在下拉列表中显示class =“ info”`文本下拉菜单中的选项在输入中输入字符。

如果我做对了，您可以这样做：

绑定输入焦点事件以在输入焦点对准时显示自动完成

<input placeholder="New fruit..." #fruitInput (focus)="matAutocomplete.showPanel = true" [formControl]="fruitCtrl" [matAutocomplete]="auto" [matChipInputFor]="chipList" [matChipInputSeparatorKeyCodes]="separatorKeysCodes" [matChipInputAddOnBlur]="addOnBlur" (matChipInputTokenEnd)="add($event)">
修改自动完成模板，以在没有输入文本或没有值匹配时显示额外的class =“ info”选项：

<mat-autocomplete #auto="matAutocomplete" (optionSelected)="selected($event)"> <mat-option class="info" *ngIf="displayedFruits.length === 0 || fruitInput.value === ''" disabled>Test</mat-option> <ng-container *ngIf="fruitInput.value !== ''"> <mat-option *ngFor="let fruit of displayedFruits" [value]="fruit"> {{fruit}} </mat-option> </ng-container> </mat-autocomplete>

正在工作的堆叠here

Angular Material => Mat-chip-通过空格键选择下拉菜单时自动完成（输入）

chip.component.ts

1 个答案: