为什么屏幕方向锁定不起作用

Question

I am trying to fix screen orientation to portrait for one page in my ionic 4 application.

using the cordova plugin: https://github.com/apache/cordova-plugin-screen-orientation

logging the current orientation and monitoring changes in orientation works fine. But when I try to lock screen orientation nothing happens and the screen continues to rotate when orientation is changed.

I am getting the following error message on android studio when the application attempts to lock the page:

2020-01-06 13:30:26.003 1913-2198/com.projectX E/Capacitor: Post message error:
java.lang.NullPointerException: Attempt to invoke virtual method 'void org.apache.cordova.CordovaPlugin.privateInitialize(java.lang.String, org.apache.cordova.CordovaInterface, org.apache.cordova.CordovaWebView, org.apache.cordova.CordovaPreferences)' on a null object reference
    at org.apache.cordova.PluginManager.getPlugin(PluginManager.java:171)
    at org.apache.cordova.PluginManager.exec(PluginManager.java:122)
    at com.getcapacitor.MessageHandler.callCordovaPluginMethod(MessageHandler.java:70)
    at com.getcapacitor.MessageHandler.postMessage(MessageHandler.java:46)
    at android.os.MessageQueue.nativePollOnce(Native Method)
    at android.os.MessageQueue.next(MessageQueue.java:326)
    at android.os.Looper.loop(Looper.java:165)
    at android.os.HandlerThread.run(HandlerThread.java:65)

Below is my app.module.ts

 import { ScreenOrientation } from '@ionic-native/screen-orientation/ngx';
 @NgModule({
   providers: [  
     ScreenOrientation    
   ],

 })

Below is the page I wish to lock orientation, map.page.ts

 import { ScreenOrientation } from '@ionic-native/screen-orientation/ngx';

 export class MapPage {

   places: Place[];
   @ViewChild(IonContent) content: IonContent;

   constructor(public platform: Platform, public renderer: Renderer, private 
      alertCtrl: AlertController, private router: Router, private placeService: 
      PlaceService, public navCtrl: NavController, private screenOrientation: 
      ScreenOrientation) {      
   }

   ngOnInit() {
     console.log("lockorientation  ");
     screen.orientation.lock('portrait');
     console.log("lockorientation  ");
   }

I was also playing around with the confix.xml file to lock the application in portrait, using:

 <preference name="orientation" value="portrait" />

But the application just ignores the command and continues to rotate.

Answer 1

在您的代码中使用它

this.screenOrientation.lock(this.screenOrientation.ORIENTATIONS.PORTRAIT);