How to reduce the size of MatSelect DropDown Panel

问题

I am trying to reduce the default size of mat-select drop-down panel, But unable to figure out how to do it

I have tried giving width , have tried overriding panel class in angular mat-select, But the size doesn't seem to go down

My Template File

    <div class="col-md-8">
       <mat-form-field style="float: right">
          <mat-select panelclass="my-panel" placeholder="Select Course"(selectionChange)="selectCourse($event,courses)" disableOptionCentering>
         <mat-option *ngFor="let course of courses" [value]="course.courseId">
          {{course.courseCode}}
        </mat-option>
      </mat-select>
    </mat-form-field>
  </div>

My Css File

 .my-panel {
   background: orange;
   height: 300px;
   display: flex;
   flex-direction: column;
   justify-content: space-between;
   min-width: 350px !important;
   }

Expected Result :

Actual Result :

New Issue

回答1:

There is a typo in your template, it needs to be panelClass and not panelclass:

<mat-select panelClass="my-panel" placeholder="Select Course"(selectionChange)="selectCourse($event,courses)" disableOptionCentering>

And as per the documentation here, the ViewEncapsulation on your component has to be set to None for this to work. It is mentioned in the comment of the example where the panelClass is being used:

  // Encapsulation has to be disabled in order for the
  // component style to apply to the select panel.

Here is a working stackblitz that has your style applied to the options.

回答2:

You can set the width of mat-select by adding the below css to the main styles.css file.

.mat-form-field-infix{
    width: 80px !important;
}

Change 80px as per your requirement.

来源：https://stackoverflow.com/questions/54103831/how-to-reduce-the-size-of-matselect-dropdown-panel