<button mat-icon-button [mat-menu-trigger-for]="themeMenu" matTooltip="更换主题！">
  <mat-icon>format_color_fill</mat-icon>
</button>

<mat-menu class="theme-picker-menu" #themeMenu="matMenu" x-position="before">
  <mat-grid-list cols="2">
    <mat-grid-tile *ngFor="let theme of themes">
      <div mat-menu-item (click)="installTheme(theme)">
        <div class="theme-picker-swatch">
          <mat-icon class="theme-chosen-icon" *ngIf="currentTheme === theme">check_circle</mat-icon>
          <div cla