XF - SignaturePad show strokes only when the touch ends

Question

I'm using SignaturePad with Xamarin.Forms and it works fine even on basic hardware devices, but I've struggled with a weird behavior with just one device: Samsung Galaxy Tab E 7.0 3G SM-T116 Tablet.

The problem is that the strokes on SignaturePad view are shown only when the touch is released from the screen. For example, if I make a long horizontal side to side line slowly, the whole stroke is invisible until I release the screen touch.

Anyone already had a similar situation? How can I workaround it?

Thanks a lot.

I've tried grow up the stroke width, thinking that it could be a screen resolution issue (the initial stroke could be too slim to see), but with no success — Diego Rafael Souza, Oct 03 '17 at 19:33
Are you somehow creating the SignaturePadView during a draw event? — Wyatt Shuler, Oct 10 '17 at 14:47
I'm not. I have a Page with the SignaturePadView, and it's created on page's initialization with some other controls. Thanks. — Diego Rafael Souza, Oct 10 '17 at 14:55
during the form's initialization or in the OnCreate() function? — Wyatt Shuler, Oct 10 '17 at 14:59
Hmmm... I'll share the code simplified code of the creation of it's page. I'm creating my view components on the pcl project, not in the specific platform. — Diego Rafael Souza, Oct 10 '17 at 15:04
Hmmm indeed... Yeah, share some of it. I'd like to take a look. — Wyatt Shuler, Oct 10 '17 at 15:05

score 3 · Accepted Answer · answered Oct 10 '17 at 14:55

I've implemented the SignaturePadView in the following way.

MainActivity.cs:

protected override void OnCreate(Bundle savedInstanceState)
{
    base.OnCreate(savedInstanceState);
    // Set our view from the "main" layout resource
    SetContentView(Resource.Layout.Main);

    Xamarin.Forms.Forms.Init(this.ApplicationContext, savedInstanceState);

    signatureView = new SignaturePadView(this);
    signatureView.StrokeWidth = 4;

    LinearLayout signatureLayout = (LinearLayout)FindViewById(Resource.Id.signatureLayout);
    signatureLayout.AddView(signatureView);

    Button btnSave = FindViewById<Button>(Resource.Id.btnSave);
    btnSave.Click += (sender, e) =>
    {
        SaveInfo();
    };

}

Here is the layout in my Main.axml:

<LinearLayout
            android:orientation="vertical"
            android:minWidth="25px"
            android:minHeight="25px"
            android:layout_width="fill_parent"
            android:layout_height="225.0dp"
            android:layout_weight="1"
            android:id="@+id/signatureLayout"
            android:background="@drawable/logosimg"
            android:gravity="center|bottom" />
    </LinearLayout>

I just have a hunch that you are creating a new SignaturePadView object or adding it to the layout after some event happens by the user.

Thank you for answer. I'm creating it on a page initialization. The user click on a button then another page is opened with the SignaturePadView and other controls. And my SignaturePadView is being created on shared code (PCL), it's the only difference I've noticed from your code — Diego Rafael Souza, Oct 10 '17 at 15:01
I kind of like the idea of creating that object in the platform specific project in the OnCreate() — Wyatt Shuler, Oct 10 '17 at 15:19
I've couldn't post my implementation yet, but I'll do it soon. I think your approach can be a way to solve my problem. Thanks again. I'll keep searching =). — Diego Rafael Souza, Oct 12 '17 at 13:57

score 1 · Answer 2 · answered Apr 22 '19 at 23:14

1

Question is a bit old now but this has been resolved in 3.0.0.

I had a similar issue on a Galaxy Tab A which was fixed by upgrading.

answered Apr 22 '19 at 23:14

Aftersow

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XF - SignaturePad show strokes only when the touch ends

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