title: Issue with zxing QRCode Scanner ( ZXing library) in android
body: <p>I am having trouble with zxing QRcode scanner. </p>
  
  <p>The version i am using is<code>me.dm7.barcodescanner:zbar:1.9</code>.</p>
  
  <p>I am getting the  following error in my console:</p>
  
  <pre><code>E/CameraPreview: java.lang.RuntimeException: cancelAutoFocus failed
    java.lang.RuntimeException: cancelAutoFocus failed
    at android.hardware.Camera.native_cancelAutoFocus(Native Method)
    at android.hardware.Camera.cancelAutoFocus(Camera.java:1302)
    at me.dm7.barcodescanner.core.CameraPreview.stopCameraPreview(CameraPreview.java:115)
    at me.dm7.barcodescanner.core.CameraPreview.surfaceDestroyed(CameraPreview.java:74)
    at android.view.SurfaceView.updateWindow(SurfaceView.java:566)
    at android.view.SurfaceView.onWindowVisibilityChanged(SurfaceView.java:239)
    at android.view.View.dispatchDetachedFromWindow(View.java:14567)
    at android.view.ViewGroup.removeAllViewsInLayout(ViewGroup.java:4792)
    at android.view.ViewGroup.removeAllViews(ViewGroup.java:4738)
    at me.dm7.barcodescanner.core.BarcodeScannerView.setupLayout(BarcodeScannerView.java:43)
    at me.dm7.barcodescanner.core.BarcodeScannerView.setupCameraPreview(BarcodeScannerView.java:87)
    at me.dm7.barcodescanner.core.CameraHandlerThread$1$1.run(CameraHandlerThread.java:31)
    at android.os.Handler.handleCallback(Handler.java:746)
    at android.os.Handler.dispatchMessage(Handler.java:95)
    at android.os.Looper.loop(Looper.java:148)
    at android.app.ActivityThread.main(ActivityThread.java:5443)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:728)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
  </code></pre>