singleTask is one of four launch modes, but its appealing name and description belies the fact that it is not recommended for general use:
http://developer.android.com/guide/topics/manifest/activity-element.html I suspect you can achieve your desired result using a general-purpose launch mode ("standard" or "singleTop"), and, instead, clearing ActivityB's taskAffinity and/or adding FLAG_ACTIVITY_NEW_TASK to the intent that launches ActivityB. On Sep 10, 11:56 pm, Olly <[email protected]> wrote: > singleTop behaves as documented for me (i.e. creating a new Activity at > the top of the stack, or reusing one if there is already an Activity > of that type at the top of the stack). I'm pretty sure singleTask is > documented incorrectly though. I'm just wondering whether I've got it > wrong, since this is completely fundamental (its in the "Android > fundamentals" document, so how has no-one else picked up on it? > > On 11 Sep, 04:30, joebowbeer <[email protected]> wrote: > > > > > I agree that the documentation is confusing and possibly wrong. > > > For the second behavior, that of discarding the intent and bringing > > the task with the specified activity to the foreground, you should use > > "singleTop" instead (despite what the documentation says). > > > On Sep 10, 4:00 pm, Olly <[email protected]> wrote: > > > > I've been learning Android and have come across an issue with > > > launchMode="singleTask". The documentation states that when this > > > attribute is used, the Activity is always launched into a new task as > > > the root Activity. Secondly, the documentation states that if an > > > Intent is targeted at such an Activity when there are Activities > > > sitting above it in its task stack, such Intents are discarded > > > (although the task is still brought to the foreground). > > > > I've been playing around with this, and the behaviour I observe is > > > completely different. In particular: - Activities with > > > launchMode="singleTask" are not always the root Activity in a task > > > stack. They are just plonked ontop of the existing stack with the same > > > affinity. - When an Intent is targeted at such an Activity and there > > > are other Activities above it in the stack, the Intent is not > > > discarded. Instead the Activities above it in the stack are discarded. > > > The Intent is then delivered via onNewIntent to the Activity as > > > normal. > > > > Can someone confirm that this is the actual behaviour? If so, why are > > > the documents incorrect? If not what have I done wrong. . . Here is a > > > simple way to observe the behaviour: > > > > 1. Create a simple main.xml containing two buttons b1 and b2. > > > 2. Create the following Activity: > > > > public class ActivityA extends Activity { > > > > @Override > > > public void onCreate(final Bundle savedInstanceState) { > > > super.onCreate(savedInstanceState); > > > setContentView(R.layout.main); > > > > Button lButton = (Button) findViewById(R.id.b1); > > > lButton.setOnClickListener(new OnClickListener() { > > > @Override > > > public void onClick(View arg0) { > > > Intent lNextIntent = new > > > Intent(ActivityA.this,ActivityA.class); > > > startActivity(lNextIntent); > > > } > > > }); > > > > Button lButton2 = (Button) findViewById(R.id.b2); > > > lButton2.setOnClickListener(new OnClickListener() { > > > @Override > > > public void onClick(View arg0) { > > > Intent lNextIntent = new > > > Intent(ActivityA.this,ActivityB.class); > > > startActivity(lNextIntent); > > > } > > > }); > > > } > > > > } > > > > 3. Create the second Activity: > > > > public class ActivityB extends ActivityA { > > > > } > > > > 4. The manifest: > > > > <?xml version="1.0" encoding="utf-8"?> > > > <manifest xmlns:android="http://schemas.android.com/apk/res/android"; > > > package="ojw28.activitytest" > > > android:versionCode="1" > > > android:versionName="1.0"> > > > <application android:icon="@drawable/icon" android:label="@string/ > > > app_name"> > > > <activity android:name="ActivityA" > > > android:label="@string/app_name"> > > > <intent-filter> > > > <action android:name="android.intent.action.MAIN" /> > > > <category > > > android:name="android.intent.category.LAUNCHER" /> > > > </intent-filter> > > > </activity> > > > <activity android:name=".ActivityB" > > > android:launchMode="singleTask"> > > > </activity> > > > </application> > > > </manifest> > > > > 5. Launch the application. Press button b1 a couple of times, see what > > > happens to the task stack using "adb shell dumpsys activity". Multiple > > > instances of ActivityA are now in the task stack as expected. > > > > Now press button b2. According to the documentation this should launch > > > an ActivityB instance is a NEW task, as the root Activity of that > > > task. Use adb to look at the stack. What actually happens is ActivityB > > > gets put ontop of the current stack, which isn't the documented > > > behaviour. > > > > Now press button b1 a couple more times. Then press b2 again. Since > > > the single instance of ActivityB isn't at the top of the stack, the > > > documentation states that this intent should be ignored. The observed > > > behaviour is that all ActivityA instances above the ActivityB instance > > > are discarded from the stack, after which the intent is delivered to > > > the instance of ActivityB as normal (via onNewIntent - you can > > > override this method and add a break point to observe this). -- 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
