ocr集成到项目中跳转LPRActivity，第一次正常使用，退出再次进入闪退，不知是什么原因

[jjjjbababy]

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.Display.getRealMetrics(android.util.DisplayMetrics)' on a null object reference at com.pcl.ocr.scanner.ScannerView.getPreviewRatio(ScannerView.java:138) at com.pcl.ocr.scanner.ScannerView.initUseCase(ScannerView.java:120) at com.pcl.ocr.scanner.ScannerView.lambda$initCamera$0$ScannerView(ScannerView.java:100) at com.pcl.ocr.scanner.-$$Lambda$ScannerView$S9Jc7nAK8ybGVA9Y6euMO_ze54w.run(Unknown Source:4) at android.os.Handler.handleCallback(Handler.java:907) at android.os.Handler.dispatchMessage(Handler.java:105) at android.os.Looper.loop(Looper.java:216) at android.app.ActivityThread.main(ActivityThread.java:7625) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:524) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:987)