Very helpful. Thanks. Richard Schilling Root Wireless
On Jun 24, 2:10 pm, Marco Nelissen <[email protected]> wrote: > On Wed, Jun 24, 2009 at 1:44 PM, Richard Schilling > <[email protected]> wrote: > > (...) > > > How does Looper know what handler class to send messages to? And, > > where does it get its messages from in the first place? When I have a > > The message usually comes from Handler.obtainMessage(), and will have its > target set to that Handler, so that the Looper knows where to send it. > > thread that calls Looper.prepare(), then Looper.loop(), then > > > Looper.exit(), it's not clear how Looper is getting messages for my > > class. Looper.loop() looks like it blocks. So, how do I make sure > > Looper.loop() doesn't stall my thread waiting for messages? > > Looper.loop() does "stall". It blocks, because it's what runs the message > loop. > > And, in the case where I want a message handler to process messages in > > > a different thread, it's not clear how Looper knows what class to send > > the messages to. The messages just seem to "come out of the sky" from > > somewhere. > > See above. > > > > > > > > 3. What do I need to do when I get the "Can't create handler inside > > > > > thread that has not called Looper.prepare()" message? > > > > You call Looper.prepare() before you create the Handler, then some time > > > later you call Looper.loop() to start the message handling loop, exactly > > as > > > done in the sample code at the top ofhttp:// > > developer.android.com/reference/android/os/Looper.html > > > If you don't want your message processing to be done in that thread, > > create > > > the Handler somewhere else (your main application thread for example). > > > Sounds good - I am envisioning my thread receiving messages somehow. > > Perhaps that's my problem here. With Looper.prepare() being called in > > my thread, how do I redirect the messages to the handler? How do I > > tell my thread to tell Looper where the handler is? > > Not sure what you mean. You normally don't have to deal with the Looper > anymore once it has been created and is running. You just use > Handler.obtainMessage() to get a Message, and then Handler.sendMessage() or > Message.sendToTarget() to send the message. > > > > > 4. How do I use LocationManager.requestLocationUpdates with Looper, > > > > > and why does this call require a Looper object? > > > > Because internally those updates are sent as Messages, so a Handler is > > > needed to receive them, so you need a Looper to run the message loop. > > > You don't *have* to specify a Looper, but in that case the calling thread > > > must have a Looper. For example, you can call the non-Looper method from > > > your app's main thread. > > > I got around my problem here by calling requestLocationUpdates > > (LocationManager.GPS_PROVIDER, 0, 0, locListen, Looper.getMainLooper > > ()). What's confusing about this is that I'm expecting locListen to > > just have gotten the messages anyway like a normal callback. This > > suggests, then, that the application's main message handler is being > > used to dispatch messages to locListen. Right? > > Yes. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/android-developers?hl=en -~----------~----~----~----~------~----~------~--~---
