Android Question MeasureStringWidth: Cannot compile

ktlua said:

I run the sample code:

Dim Canvas1 As Canvas
Dim width As Float
Dim t As String
t = "Text to write"
width = Canvas1.MeasureStringWidth(t, Typeface.DEFAULT, 14)

The error is:java.lang.NullPointerException

May I know where is my error?

Thanks.

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Widget said:

Sure. Your Canvas1 hasn't been initialized so it is still NULL.

Canvas1 would normally be the canvas of the view you are going to write to.

Canvas1.Initialize(Panel1)
width = Canvas1.MeasureStringWidth(t, Typeface.DEFAULT, 14)​

or you can use a Bitmap

Private MyBitmap as Bitmap
MyBitmap.InitializeMutable(1,1) 'Ignore
Canvas1.Initialize(MyBitmap)
width = Canvas1.MeasureStringWidth(t, Typeface.DEFAULT, 14)​

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ktlua said:

Yes, I tried to initialize it with a label generated from codes. But it does not work.

Dim Canvas1 as Canvas
Dim lbl as Label
Dim width as Float
Label.Initialize("Label")
Canvas1.Initialize(lbl)
width = Canvas1.MeasureStringWidth(t, Typeface.DEFAULT, 14)

I can initialize Canvas by a Label from Designer but not from codes.

Pleaes help. Thank you!

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DonManfred said:

The label must be added to the activity first before you can use it.
I suggest to use an mutable bitmap to initialize the canvas

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