问离子语音识别-运行时错误对象(.)不是hasPermission中的一个函数

EN

import { SpeechRecognition } from '@ionic-native/speech-recognition/ngx';
.....
providers: [
StatusBar,
SplashScreen,
SpeechRecognition,
{provide: ErrorHandler, useClass: IonicErrorHandler}]

import { SpeechRecognition } from '@ionic-native/speech-recognition/ngx';
import { AlertController } from 'ionic-angular';
......
constructor (private sr: SpeechRecognition, private alertCtrl: AlertController)
......
ngonInit() {
try {
      this.sr.hasPermission().then((permission: boolean) => {
        if(!permission) {
          this.sr.requestPermission().then(
            () => console.log("Granted"),
            () => console.log("Denied")
          );
        }
      });
    }
    catch(err) {
      let alert = this.alertCtrl.create({
        title: "x_x",
        message: "Opps! couldn't get permission!",
        buttons: [{
          text: "cancel",
          role: 'cancel',
          handler: () => {}
        }]
      });
      console.log(err);   //ERROR LOGGED
      alert.present();
    }
}

start() {
    try {
      this.sr.startListening().subscribe((matches: Array<string>) => {
        console.log(matches);
        this.msg= matches[0];
      });
    }
    catch(err) {
      let alert = this.alertCtrl.create({
        title: "x_x",
        message: "Opps! something is wrong!",
        buttons: [{
          text: "cancel",
          role: 'cancel',
          handler: () => {}
        }]
      });
      console.log(err);    // ERROR LOGGED if ngOnInit kept empty
      alert.present();
    }
  }