Hello, I am still waiting and hoping for some suggestions on single instance.
As per my experiments results, either I have not understood Google documentation properly or its behavior is different from Google documentation. Kindly suggest. Thanks, Vibhor On Tue, Jun 22, 2010 at 3:00 PM, Vibhor Mahajan <[email protected]>wrote: > Hello, > > Simply saying, I am trying to understand the behavior of singleinstance in > detail. I found 2 different behaviors when a activity with singleinstance > launchmode, launches an another activity. > > Based on your reply, I understood SINGLEINSTANCE activity is launching an > activity in new task and because destination activity is already on top of > desired task, task is brought to foreground and new instance is not created. > I accept, it is special and should be used carefully. > > But, it is contradicting to results stated in my previous message. Kindly > give suggestions for the questions in my previous message for better > understanding. > > Thanks, > Vibhor > > > On Tue, Jun 22, 2010 at 2:07 PM, Dianne Hackborn <[email protected]>wrote: > >> Yes that is working as intended, you have B and C together in their own >> task, and A can't be in it because it is single instance. >> >> Again, just ignore single instance unless you have a clear reason for >> using it, and then you will want to structure the rest of your interaction >> to work well with it. >> >> At this point I would suggest focusing questions on what you are actually >> trying to accomplish. >> >> >> On Tue, Jun 22, 2010 at 1:31 AM, Vibhor Mahajan <[email protected] >> > wrote: >> >>> Hello, >>> >>> Thanks Dianne for reply. I understood your point. But after doing some >>> more tests I have confusions. Kindly provide some suggestions. >>> >>> Activity A has SINGLEINSTANCE and B & C has STANDARD launch mode. >>> Execute below steps: >>> 1. Start A from launcher >>> 2. Launch B from A. (oncreate of B is called) >>> 3. Launch A from B. (re-starts A because A has SINGLEINSTANCE launchmode) >>> 4. Launch C from A. (oncreate of C is called) >>> 5. Launch A from C. (re-starts A because A has SINGLEINSTANCE launchmode) >>> 6. Launch B from A again. >>> >>> From step 6 above, instance of B is NOT CREATED instead task containing >>> activity B & C comes in foreground, with last state of C (from step4) >>> displayed. (because C was on top of this task). >>> >>> Similar behavior is documented in >>> http://developer.android.com/guide/topics/fundamentals.html link. "If it >>> does, it is not in position to handle the intent, and the intent is dropped. >>> (Even though the intent is dropped, its arrival would have caused the task >>> to come to the foreground, where it would remain.)" >>> >>> Q1) Why new instance of B is not created even though B has standard >>> launch mode and also not top of destination task? >>> >>> Now if I change the implementation as below: >>> Activity A has STANDARD and B has SINGLEINSTANCE launch mode. >>> Repeat same steps again: >>> 1. Start A from launcher >>> 2. Launch B from A. (oncreate of B is called) >>> 3. Launch A from B. (a new instance of A is created, in the same task in >>> which A's instance was created in step 1. Now stack is A - A) >>> 4. Launch B from A re-starts B. >>> 5. Launch A from B. (a new instance of A is created, in the same task in >>> which A's instance was created in step 1. Now stack is A - A - A) >>> >>> Executing step 4 & 5 repeatedly, creates multiple instances of A. >>> >>> Q2) Step 3 & 5, B creates an intent to start A with >>> FLAG_ACTIVITY_NEW_TASK. Why new instance of A is created in same task in >>> which A was launched from launcher? >>> Q3) Shouldn't the behavior be same as explained in previous message i.e. >>> A should be brought to foreground? >>> >>> Thanks, >>> Vibhor >>> >>> On Tue, Jun 22, 2010 at 10:41 AM, Dianne Hackborn <[email protected] >>> > wrote: >>> >>>> First, you almost certainly don't want to use singleInstance. It is >>>> for very special situations, and has significant repercussions on UI flow >>>> that you need to understand before touching it. >>>> >>>> The key point about this is this statement in "Launch modes" >>>> http://developer.android.com/guide/topics/fundamentals.html#lmodes >>>> >>>> >>>> <http://developer.android.com/guide/topics/fundamentals.html#lmodes>*Whether >>>> the instance can have other activities in its task*. A "singleInstance" >>>> activity stands alone as the only activity in its task. If it starts >>>> another >>>> activity, that activity will be launched into a different task regardless >>>> of >>>> its launch mode — as if FLAG_ACTIVITY_NEW_TASK was in the intent. In >>>> all other respects, the "singleInstance" mode is identical to " >>>> singleTask". >>>> >>>> This means that when you launch B, it is the root of its own new task. >>>> When you launch B again, the task for it already exists, then the current >>>> task will be brought to the foreground instead of starting a new instance. >>>> You have effectively turned yourself into a launcher, so get the behavior >>>> expected for a launcher. >>>> >>>> On Mon, Jun 21, 2010 at 9:45 PM, Vibhor Mahajan < >>>> [email protected]> wrote: >>>> >>>>> Hello, >>>>> >>>>> As per the documentation, standard and singletop differ in just one >>>>> way, standard activity instance is created every time but singletop >>>>> instance >>>>> may or may not be created. I verified this, if in the above code, reverse >>>>> launchmode of activity A & B i.e. Now A has STANDARD and B as >>>>> SINGLEINSTANCE. >>>>> >>>>> Repeat same steps again: >>>>> 1. Click button in Activity A starts B. (oncreate of B is called) >>>>> 2. Click button in Activity B creates a new instance A. (oncreate of A >>>>> is called, because A now has STANDARD launchmode) >>>>> 3. Click button in Activity A re-starts B. (oncreate of B is NOT >>>>> CALLED, because B now has SINGLEINSTANCE launchmode) >>>>> >>>>> This is exactly as per the documentation. >>>>> >>>>> Kindly help in understanding why in original source code, multiple >>>>> instances of B is not created, though B is having STANDARD launch mode? >>>>> >>>>> Thanks, >>>>> Vibhor >>>>> >>>>> >>>>> On Mon, Jun 21, 2010 at 8:15 PM, MobDev <[email protected]>wrote: >>>>> >>>>>> Btw, got this from documentation, concentrate on the last sentence : >>>>>> "Every time there's new intent for a "standard" activity, a new >>>>>> instance of the class is created to respond to that intent. Each >>>>>> instance handles a single intent. Similarly, a new instance of a >>>>>> "singleTop" activity may also be created to handle a new intent. >>>>>> However, if the target task already has an existing instance of the >>>>>> activity at the top of its stack, that instance will receive the new >>>>>> intent (in an onNewIntent() call); a new instance is not created." >>>>>> found here : >>>>>> >>>>>> http://developer.android.com/guide/topics/manifest/activity-element.html#lmode >>>>>> >>>>>> On 21 jun, 13:30, Vibhor Mahajan <[email protected]> wrote: >>>>>> > Hello, >>>>>> > >>>>>> > What is launch mode of an activity, which is launched from an >>>>>> activity >>>>>> > with launch mode as "singleinstance". I tried the following code. >>>>>> > >>>>>> > My application has two activities i.e. A & B. Activity A has >>>>>> > "singleinstance" launchmode set and activity B has "standard" launch >>>>>> > mode set. Android manifest file is as follows: >>>>>> > >>>>>> > <application android:icon="@drawable/icon" android:label="@string/ >>>>>> > app_name" > >>>>>> > <activity android:name=".activity_lifecycle" >>>>>> > android:label="@string/app_name" >>>>>> > android:launchMode="singleInstance"> >>>>>> > <intent-filter> <action >>>>>> > android:name="android.intent.action.MAIN" /> >>>>>> > <category >>>>>> > android:name="android.intent.category.LAUNCHER" /> >>>>>> > </intent-filter> >>>>>> > </activity> >>>>>> > <activity android:name=".another" >>>>>> > android:launchMode="standard" ></activity> >>>>>> > </application> >>>>>> > >>>>>> > Activity A has a button, clicking button starts Activity B using >>>>>> below >>>>>> > code: >>>>>> > public void onClick(View v) { >>>>>> > // TODO Auto-generated method stub >>>>>> > Intent intent = new >>>>>> > Intent(activity_lifecycle.this,another.class); >>>>>> > startActivityForResult(intent, 0); >>>>>> > >>>>>> > } >>>>>> > >>>>>> > Activity B has a button, clicking button starts Activity A using >>>>>> below >>>>>> > code: >>>>>> > public void onClick(View v) { >>>>>> > // TODO Auto-generated method stub >>>>>> > Intent intent = new >>>>>> > Intent(another.this,activity_lifecycle.class); >>>>>> > startActivityForResult(intent, 0); >>>>>> > >>>>>> > } >>>>>> > >>>>>> > Click button in Activity A starts B. (oncreate of B is called) >>>>>> > Click button in Activity B re-starts A. (because A has >>>>>> SINGLEINSTANCE >>>>>> > launchmode) >>>>>> > Click button in Activity A re-starts B. (oncreate of B is NOT >>>>>> CALLED) >>>>>> > >>>>>> > After 3rd step, since activity B is standard, a new instance should >>>>>> be >>>>>> > created and not previous instance to be used. >>>>>> > >>>>>> > Kindly suggest why when second time activity B is started, a new >>>>>> > instance of activity B is not created, when it is declared with >>>>>> > launchmode "standard". >>>>>> > >>>>>> > Regards, >>>>>> > Vibhor >>>>>> >>>>>> -- >>>>>> 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]<android-developers%[email protected]> >>>>>> For more options, visit this group at >>>>>> http://groups.google.com/group/android-developers?hl=en >>>>>> >>>>> >>>>> -- >>>>> 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]<android-developers%[email protected]> >>>>> For more options, visit this group at >>>>> http://groups.google.com/group/android-developers?hl=en >>>>> >>>> >>>> >>>> >>>> -- >>>> Dianne Hackborn >>>> Android framework engineer >>>> [email protected] >>>> >>>> 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 >>>> [email protected] >>>> To unsubscribe from this group, send email to >>>> [email protected]<android-developers%[email protected]> >>>> For more options, visit this group at >>>> http://groups.google.com/group/android-developers?hl=en >>>> >>> >>> -- >>> 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]<android-developers%[email protected]> >>> For more options, visit this group at >>> http://groups.google.com/group/android-developers?hl=en >>> >> >> >> >> -- >> Dianne Hackborn >> Android framework engineer >> [email protected] >> >> 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 [email protected] >> To unsubscribe from this group, send email to >> [email protected]<android-developers%[email protected]> >> For more options, visit this group at >> http://groups.google.com/group/android-developers?hl=en >> > > -- 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
