[android-developers] Re: Handler and MessageQueue question
Yes, it helps me a lot! I was really confused about that. Thanks, Greg! ;) On Sat, Apr 4, 2009 at 4:37 AM, Greg Krimer gkri...@gmail.com wrote: Hi Taísa, I am reversing the order of your questions. Did you say the main thread has its own handler?! So, if mine no more exists, the it will handle that message? As Dianne said, your handler is not associated with the activity. The behavior of your handler is not influenced by the state of the activity in which it was created. The handler does not know or care that the activity is finished. Instead, the handler is associated with the messages that are destined for it. When you create a message and send it to some handler, a reference to the handler is placed into the target field of the message. So long as there are messages in the queue with your handler as the target, your handler will be called to service them. When there are no more messages in the queue whose target is your handler then, assuming there are no references to your handler anywhere else, your handler will be garbage collected like all normal objects. There is no magical link between your handler and the activity. So, it's not ugly to finish my Activity and let that message in the MessageQueue of the main thread? :) It is not ugly, but it may or may not be what you want. It depends on the action that the message triggers. I had just this same situation. In my case, the message after the killer message would have triggered an action that is not valid once the activity is finished. Since there is no magic link between the handler and the activity I had to make one: I implemented handleMessage() in such a way that it dropped messages if the activity was finished. In your case, if the message after the killer message is handled harmlessly when the activity is finished then you don't need to do anything special about it. Just leave it in the queue and it let your handler take care of it. Hope this helps. Greg On Apr 3, 11:31 am, Taísa Cristina taisa.san...@gmail.com wrote: On Fri, Apr 3, 2009 at 3:21 PM, Dianne Hackborn hack...@android.com wrote: Provided your process doesn't get killed, your process's main thread will handle that message whenever it comes up, regardless of what happened to the activity. Handler doesn't know anything about the activity state. On Fri, Apr 3, 2009 at 11:17 AM, Taísa Cristina taisa.san...@gmail.comwrote: Hi all, I have a Handler implementation that is used in my Activity. While handling the messages, there's a value of msg.what which makes my Activity to finish itself. My problem is that, when that killer message arrives, there's another one in the message queue also destined to my handler. In this case, what happens if I just finish my Activity? I could see that no exception raised. But, who will handle this lost message since its Handler no longer exists? ** I have another Activity receiving messages containing the same data as the killer one. So, [ I think ] I can't use removeMessage(what, obj). Taísa -- Dianne Hackborn Android framework engineer hack...@android.com Note: please don't send private questions to me, as I don't have time to provide private support, and so won't reply to such e-mails. All such questions should be posted on public forums, where I and others can see and answer them. -- Taísa Cristina Costa dos Santos Computer Engineer Brazil, SP 55 19 8152-7453 -- Taísa Cristina Costa dos Santos Computer Engineer Brazil, SP 55 19 8152-7453 --~--~-~--~~~---~--~~ 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 -~--~~~~--~~--~--~---
[android-developers] Re: Handler and MessageQueue question
Hi Taísa, I am reversing the order of your questions. Did you say the main thread has its own handler?! So, if mine no more exists, the it will handle that message? As Dianne said, your handler is not associated with the activity. The behavior of your handler is not influenced by the state of the activity in which it was created. The handler does not know or care that the activity is finished. Instead, the handler is associated with the messages that are destined for it. When you create a message and send it to some handler, a reference to the handler is placed into the target field of the message. So long as there are messages in the queue with your handler as the target, your handler will be called to service them. When there are no more messages in the queue whose target is your handler then, assuming there are no references to your handler anywhere else, your handler will be garbage collected like all normal objects. There is no magical link between your handler and the activity. So, it's not ugly to finish my Activity and let that message in the MessageQueue of the main thread? :) It is not ugly, but it may or may not be what you want. It depends on the action that the message triggers. I had just this same situation. In my case, the message after the killer message would have triggered an action that is not valid once the activity is finished. Since there is no magic link between the handler and the activity I had to make one: I implemented handleMessage() in such a way that it dropped messages if the activity was finished. In your case, if the message after the killer message is handled harmlessly when the activity is finished then you don't need to do anything special about it. Just leave it in the queue and it let your handler take care of it. Hope this helps. Greg On Apr 3, 11:31 am, Taísa Cristina taisa.san...@gmail.com wrote: On Fri, Apr 3, 2009 at 3:21 PM, Dianne Hackborn hack...@android.com wrote: Provided your process doesn't get killed, your process's main thread will handle that message whenever it comes up, regardless of what happened to the activity. Handler doesn't know anything about the activity state. On Fri, Apr 3, 2009 at 11:17 AM, Taísa Cristina taisa.san...@gmail.comwrote: Hi all, I have a Handler implementation that is used in my Activity. While handling the messages, there's a value of msg.what which makes my Activity to finish itself. My problem is that, when that killer message arrives, there's another one in the message queue also destined to my handler. In this case, what happens if I just finish my Activity? I could see that no exception raised. But, who will handle this lost message since its Handler no longer exists? ** I have another Activity receiving messages containing the same data as the killer one. So, [ I think ] I can't use removeMessage(what, obj). Taísa -- Dianne Hackborn Android framework engineer hack...@android.com Note: please don't send private questions to me, as I don't have time to provide private support, and so won't reply to such e-mails. All such questions should be posted on public forums, where I and others can see and answer them. -- Taísa Cristina Costa dos Santos Computer Engineer Brazil, SP 55 19 8152-7453 --~--~-~--~~~---~--~~ 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 -~--~~~~--~~--~--~---
[android-developers] Re: Handler and MessageQueue question
Provided your process doesn't get killed, your process's main thread will handle that message whenever it comes up, regardless of what happened to the activity. Handler doesn't know anything about the activity state. On Fri, Apr 3, 2009 at 11:17 AM, Taísa Cristina taisa.san...@gmail.comwrote: Hi all, I have a Handler implementation that is used in my Activity. While handling the messages, there's a value of msg.what which makes my Activity to finish itself. My problem is that, when that killer message arrives, there's another one in the message queue also destined to my handler. In this case, what happens if I just finish my Activity? I could see that no exception raised. But, who will handle this lost message since its Handler no longer exists? ** I have another Activity receiving messages containing the same data as the killer one. So, [ I think ] I can't use removeMessage(what, obj). Taísa -- Dianne Hackborn Android framework engineer hack...@android.com Note: please don't send private questions to me, as I don't have time to provide private support, and so won't reply to such e-mails. All such questions should be posted on public forums, where I and others can see and answer them. --~--~-~--~~~---~--~~ 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 -~--~~~~--~~--~--~---
[android-developers] Re: Handler and MessageQueue question
So, it's not ugly to finish my Activity and let that message in the MessageQueue of the main thread? :) On Fri, Apr 3, 2009 at 3:21 PM, Dianne Hackborn hack...@android.com wrote: Provided your process doesn't get killed, your process's main thread will handle that message whenever it comes up, regardless of what happened to the activity. Handler doesn't know anything about the activity state. Did you say the main thread has its own handler?! So, if mine no more exists, the it will handle that message? On Fri, Apr 3, 2009 at 11:17 AM, Taísa Cristina taisa.san...@gmail.comwrote: Hi all, I have a Handler implementation that is used in my Activity. While handling the messages, there's a value of msg.what which makes my Activity to finish itself. My problem is that, when that killer message arrives, there's another one in the message queue also destined to my handler. In this case, what happens if I just finish my Activity? I could see that no exception raised. But, who will handle this lost message since its Handler no longer exists? ** I have another Activity receiving messages containing the same data as the killer one. So, [ I think ] I can't use removeMessage(what, obj). Taísa -- Dianne Hackborn Android framework engineer hack...@android.com Note: please don't send private questions to me, as I don't have time to provide private support, and so won't reply to such e-mails. All such questions should be posted on public forums, where I and others can see and answer them. -- Taísa Cristina Costa dos Santos Computer Engineer Brazil, SP 55 19 8152-7453 --~--~-~--~~~---~--~~ 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 -~--~~~~--~~--~--~---
