This has been asked before by Daren (here http://groups.google.com/group/android-developers/browse_thread/thread/ab41256a0f57cd44/0c082d62ed206733 and here http://groups.google.com/group/android-developers/browse_thread/thread/3e6276e775b9685b/8b37670956c9b03f) and even though Romain Guy replied, his replies didn't really answer the questions. Here's another try:
When doing scrolling animation in View's computeScroll(), we cannot access the members mScrollX and mScrollY directly. They are hidden from the API; funnily enough, Google doesn't seem to eat their own dog food, meaning, they don implement their own apps against the API. For instance, Launcher and Launcher2 both access these members directly to create Android's home screen flinging (http:// android.git.kernel.org/?p=platform/packages/apps/ Launcher2.git;a=blob_plain;f=src/com/android/launcher2/ Workspace.java;hb=master). Instead of accessing these members, one should call scrollTo() with the desired X and Y parameters. scrollTo() then in turn calls invalidate() which should make the screen being redrawn and computeScroll() being called again, thus, creating a sort of animation loop. Unfortunately, as Daren pointed out, invalidate() does not seem to cause computeScroll() being called again. Nothing animates. Calling postInvalidate() however does the trick. Hence, my current workaround is to call scrollTo(), followed by postInvalidate(). This seems ugly since now both invalidate() and postInvalidate() are being called at the same time. >From looking at the postInvalidate() code I don't see how it is any different from invalidate(). It is simply an invalidate() call posted into the main thread's message queue. 1. Can anyone clarify why postInvalidate() works, while invalidate() doesn't? 2. What is the correct way to implement computeScroll(), without calling both invalidate() and postInvalidate()? Thanks, -Jonas -- You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
