解决 NullInjectorError：没有 MatDialogRef 的提供者

typescript
import { Component, Inject } from '@angular/core';
import { MatDialog, MatDialogRef, MAT_DIALOG_DATA } from '@angular/material/dialog';
@Component({
  selector: 'app-dialog-example',
  template: `
    
Dialog Example
    Open Dialog
  `
})
export class DialogExampleComponent {
  constructor(public dialog: MatDialog) {}
  openDialog(): void {
    const dialogRef = this.dialog.open(DialogContentComponent, {
      width: '250px',
      data: { name: 'John' }
    });
    dialogRef.afterClosed().subscribe(result => {
      console.log('Dialog closed', result);
      // 执行关闭对话框后的操作
    });
  }
}
@Component({
  selector: 'app-dialog-content',
  template: `
    
Dialog Content
    
      
Dialog content goes here.
      
Received data: {{ data.name }}
    
    
      Close
    
  `
})
export class DialogContentComponent {
  constructor(
    public dialogRef: MatDialogRef,
    @Inject(MAT_DIALOG_DATA) public data: any
  ) {}
}