android:launchMode

[Android] android:launchMode (standard、singleTop、singleTask、singleInstance)
http://jiunway.blogspot.com/2010/10/android-androidlaunchmode_26.html

standard, no reuse activity
singleTop, reuse activity if the same as the toppest activity
singleTask, reuse the same activity on the activity stack
singleInstance, reuse the same activity across multiple processes