cactustictacs
2020-12-24 19:28:09
You need to pass that AttributeSet parameter into the View superclass constructor:
To allow Android Studio to interact with your view, at a minimum you must provide a constructor that takes a
Contextand anAttributeSetobject as parameters. This constructor allows the layout editor to create and edit an instance of your view.
(https://developer.android.com/training/custom-views/create-view#subclassview)
So:
class CustomView(context: Context?,attributeSet: AttributeSet) : View(context, attributeSet) {
If you like, this is the standard boilerplate, overloaded custom view constructor (that the IDE will generate for you):
class CustomView @JvmOverloads constructor(
context: Context,
attrs: AttributeSet? = null,
defStyleAttr: Int = 0
) : View(context, attrs, defStyleAttr)
That has some edge case theming compromises but it's usually fine, and handles whichever constructor the system wants to use.
(Also you don't need that nested CustomView class in your code)
this worked for me. But one more thing how do I get and update the number property and display the updated value in the fragment?
Are you sure you want to create a custom view? If so you should read some tutorials on it, it's a little advanced. If not my advice is don't bother, stick a
TextViewin your fragment's layout and update it in your fragment code. If you're a beginner, you really don't want to do this unless you have to!Basically I wanted to implement it on a paint app where a CustomView serves as a canvas to draw and it will be inflated inside the fragment. So, I wanted to modify the pen size and color from the fragment. Before, I could do that I thought it would be better to understand how things work with a basic example, so I chose this. I am planning to have a public pen size property inside the custom view which I can update from the fragment and start to draw with new pen size.
Ok, you really need to read up on this, but you can either inflate a layout inside your custom view (like with a Fragment), or you can draw to a
Canvas, which is what you want to do. You basically implementonDrawand use the drawing commands (likedrawTextordrawLine) using aPaint. So if you want to write a number, you can usedrawText. But honestly, I feel like what you're doing is one of the more advanced uses of custom views (touch and everything) so finding a paint app tutorial might be your best bet, something that shows you how it all basically works