Difference between SurfaceView and View

Question

When is it necessary  or better to use a SurfaceView instead of a View

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A SurfaceView is a custom view in Android that can be used to drawn inside it  The main difference between a View and a SurfaceView is that a View is drawn in the UI Thread  which is used for all the user interaction  If you want to update the UI rapidly enough and render a good amount of information in it  a SurfaceView is a better choice    But there are a few technical insides to the SurfaceView    1   They are not hardware accelerated   2   Normal views are rendered when you call the methods invalidate or postInvalidate    but this does not mean the view will be     immediately updated  A VSYNC will be sent  and the OS decides when     it gets updated  The SurfaceView can be immediately updated   3   A SurfaceView has an allocated surface buffer  so it is more costly

User · Answer

Why use SurfaceView and not the classic View class     One main reason is that SurfaceView can rapidly render the screen   In simple words a SV is more capable of managing the timing and render animations   To have a better understanding what is a SurfaceView we must compare it with the View class   What is the difference    check this simple explanation in the video  https   m youtube com watch feature youtu be amp v eltlqsHSG30  Well with the View we have one major problem    the timing of rendering animations   Normally the onDraw   is called from the Android run-time system   So  when Android run-time system calls onDraw   then the application cant control  the timing of display  and this is important for animation  We have a gap of timing  between the application  our game  and the Android run-time system   The SV it can call the onDraw   by a dedicated Thread   Thus  the application controls the timing  So we can display the next bitmap image of the animation

User · Answer

One of the main differences between surfaceview and view is that to refresh the screen for a normal view we have to call invalidate method from the same thread where the view is defined  But even if we call invalidate  the refreshing does not happen immediately  It occurs only after the next arrival of the VSYNC signal  VSYNC signal is a kernel generated signal which happens every 16 6 ms or this is also known as 60 frame per second  So if we want more control over the refreshing of the screen  for example for very fast moving animation   we should not use normal view class   On the other hand in case of surfaceview  we can refresh the screen as fast as we want and we can do it from a background thread  So refreshing of the surfaceview really does not depend upon VSYNC  and this is very useful if we want to do high speed animation  I have few training videos and example application which explain all these things nicely  Please have a look at the following training videos   https   youtu be kRqsoApOr9U  https   youtu be Ji84HJ85FIQ  https   youtu be U8igPoyrUf8

User · Answer

updated 05 09 2014  OK  We have official document now  It talked all I have mentioned  in a better way     Read more detailed here   Yes  the main difference is surfaceView can be updated on the background thread  However  there are more you might care    surfaceView has dedicate surface buffer while all the view shares one surface buffer that is allocated by ViewRoot  In another word  surfaceView cost more resources  surfaceView cannot be hardware accelerated  as of JB4 2  while 95  operations on normal View are HW accelerated using openGL ES  More work should be done to create your customized surfaceView  You need to listener to the surfaceCreated Destroy Event  create an render thread  more importantly  synchronized the render thread and main thread  However  to customize the View  all you need to do is override onDraw method  The timing to update is different  Normal view update mechanism is constraint or controlled by the framework You call view invalidate in the UI thread or view postInvalid in other thread to indicate to the framework that the view should be updated  However  the view won t be updated immediately but wait until next VSYNC event arrived  The easy approach to understand VSYNC is to consider it is as a timer that fire up every 16ms for a 60fps screen  In Android  all the normal view update  and display actually but I won t talk it today   is synchronized with VSYNC to achieve better smoothness  Now back to the surfaceView  you can render it anytime as you wish  However  I can hardly tell if it is an advantage  since the display is also synchronized with VSYNC  as stated previously

User · Answer

A few things I ve noted    SurfaceViews contain a nice rendering mechanism that allows threads to update the surface s content without using a handler  good for animation    Surfaceviews cannot be transparent  they can only appear behind other elements in the view hierarchy   I ve found that they are much faster for animation than rendering onto a View    For more information  and a great usage example  refer to the LunarLander project in the SDK  s examples section

User · Answer

Views are all drawn on the same GUI thread which is also used for all user interaction   So if you need to update GUI rapidly or if the rendering takes too much time and affects user experience then use SurfaceView

User · Answer

The main difference is that SurfaceView can be drawn on by background theads but Views can t  SurfaceViews use more resources though so you don t want to use them unless you have to

[android] Difference between SurfaceView and View?

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