片段中的回调

编程问答 2022-08-15

问题描述

当我尝试在Fragment的ISurfaceHolderCallback中添加callback时， 我遇到错误system.invalidCastException: 'Specified cast is not valid.' 

 public override View OnCreateView(LayoutInflater inflater,ViewGroup container,Bundle savedInstanceState)
        {
            View view = inflater.Inflate(Resource.Layout.qr_main,container,false);
            var metrics = Resources.displayMetrics;
            var height = metrics.HeightPixels;
            var width = metrics.WidthPixels;

            cameraPreview = view.FindViewById<SurfaceView>(Resource.Id.cameraPreview);
            txtResult = view.FindViewById<TextView>(Resource.Id.txtResult);

            barcodeDetector = new BarcodeDetector.Builder(this.Activity)
                .SetBarcodeFormats(BarcodeFormat.QrCode)
                .Build();
            cameraSource = new CameraSource
                .Builder(this.Activity,barcodeDetector)
                .SetRequestedPreviewSize(height,width)
                .SetRequestedFps(30.0f)
                .SetAutoFocusEnabled(true)
                .Build();

            cameraPreview.Holder.AddCallback((ISurfaceHolderCallback)this.Activity);
            barcodeDetector.SetProcessor((IProcessor)this.Activity);

            return view;
        }

请帮助我..谢谢

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androidandroidcallbackfragmentfragmentxamarinxamarin