How to implement scrolling in Android custom view

Question

I've written a custom view which I'd like to ensure is viewable on any screen size.

I've overridden the onMeasure:

@Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { super.onMeasure(widthMeasureSpec, heightMeasureSpec); int parentWidth = MeasureSpec.getSize(widthMeasureSpec); int parentHeight = MeasureSpec.getSize(heightMeasureSpec); this.setMeasuredDimension(parentWidth, parentHeight); }

and this seems to work fine when the view is smaller than the screen. Sometimes, though, the custom view is larger than the screen, and I'm planning for smaller screen sizes, so I wrapped the custom view in a ScrollView but now the parentHeight in the onMeasure comes out as 0.

I've changed the superclass of the custom view from View to ScrollView, hoping for an easy win of inheriting the scrolling functionality, but this hasn't happened so I'm left with trying to find a way of getting the ScrollView functionality to work with my custom view, or writing my own scrolling functionality.

Has anyone any advice? I've seen this post on Large Image Scrolling Using Low Level Touch Events and was going to copy some of that functionality if I'm forced to write my own, but would appreciate a nudge in the right direction either way.

What layout properties have you set to the parent ScrollView? — rds
– rds, Commented Jul 20, 2011 at 8:37

Martyn · Accepted Answer · 2011-07-20 18:07:27Z

Turns out the answer was simple. I left the ScrollView in and changed my onMeasure. The thing to note about it is that although Android would supply the width, it wouldn't supply me with a height, which was initially confusing. To just get the view to fill the available space I grabbed the visible rect of the parent view. Code in full (hopefully it'll help someone else who is having the same problem):

@Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { super.onMeasure(widthMeasureSpec, heightMeasureSpec); int parentWidth = MeasureSpec.getSize(widthMeasureSpec); int parentHeight; if(isLandscape()) { Rect r = new Rect(); ((ScrollView)getParent()).getGlobalVisibleRect(r); parentHeight = r.bottom - r.top; } else { parentHeight = (int) Util.getViewHeight(); } this.setMeasuredDimension(parentWidth, parentHeight); }

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