Inheriting View

To inherit from View class we have to consider on minimal 2 method after its Constructor. The two methods are onMeasure() and onDraw() method. These two method take an important role in viewing the component on the screen.

onMeasure() is a method to calculate component boundary before drawing the component. So, when we want some additional dimension unit in width / height we have to take it in this method. The declaratin of this method is just like below:

protected void onMeasure(int widthMeasureSpec, 
int heightMeasureSpec)

where widthMeasureSpec and heightMeasureSpec is for width and height measure spec.

onDraw() is a method for drawing component.

Ancestor method contains empty code, so we have to draw our component in this method. The declaration of this method is like below:

protected void onDraw(Canvas canvas)

For clearly source, please take a look at the source code attached to this document. 

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