第 57 课：关闭失败时显示提示

@State closing: boolean = false
@State errorMessage: string = ''

async close(): Promise<void> {
  if (this.closing || this.handle.isClosed()) return
  this.closing = true
  try { await this.handle.close() }
  catch {
    this.errorMessage = '关闭失败，请重试'
    console.error('Handle.close failed')
  } finally { this.closing = false }
}

build() {
  Column() {
    Button(this.handle.isClosed() ? '已关闭' : this.closing ? '关闭中…' : '关闭')
      .enabled(!this.closing && !this.handle.isClosed())
      .onClick(() => { this.close() })
    if (this.errorMessage.length > 0) { Text(this.errorMessage) }
  }
}