默认单选按钮选择不起作用

Question

默认情况下未选择选择默认单选按钮。

<div class="form-group">
    <label for="">Activity Time</label><br/>
    <input type="radio" value="0" (change)="handleActivityTime(true)" [checked]="true"  formControlName="activityTime"> By Select
    <input type="radio" value="1" (change)="handleActivityTime(false)"   formControlName="activityTime"> By Input
</div>