The four ways Android boots are standard,singletop,singletask,singleinstence, respectively.
Standard is the most common way to start an activity and is the default way to start. When you start an activity, he goes to the top of the stack at the back of the stack. The system does not control whether the stack has the same activity, in the same way as after-in first-out.
Singletop mode is when the activity starts, the system first determines whether the top of the stack has the same activity, if there is no new activity, otherwise it will not create a new activity. But to use him directly.
Singletask mode at the start of the activity, the system first determine whether there is an instance of the activity in the stack, if there is no new instance, if there is a stack of existing activities above the stack.
The singleinstance mode creates a new stack when it is started, and is the same instance when other programs access the activity to initiate the activity, and all applications access the same instance.
In the experimental application B to access activity A with SingleInstance startup mode, you need to be aware that you want to add the Androidmanifest.xml in the A application.
<activity android:name= "com.example.testandroid.BActivity" android:exported= "true" >
</activity>
Android:exported= "True" This is a statement that the activity can be opened by other apps
Reference: http://www.cnblogs.com/lwbqqyumidi/p/3793440.html
Android activity launches 4 ways to record and open other apps ' activity pits