J2ME - MIDlet lifecycle explained

MIDlet is the basic execution unit in J2ME and it is in different states in different point of its execution. When you launch an application, operating system loads it up. There are three basic states of a MIDlet:

1. PAUSED
2. DESTOYED
3. ACTIVE

The names are self explanatory. When the application initially loads, its in the PAUSED state. When application starts execution, it transitions from PAUSED to ACTIVE state but before going to active state, startApp() method of the MIDlet is called which you must implement in your MIDlet class.

There are several instances where you yourself or the operating system will request your MIDlet to be paused for example in an event of an incoming call. When your application is requested to be paused, it goes from ACTIVE to PAUSED state and before it gets pasued, pauseApp() method is executed. If you want to stop or pause any running threads in your app while it is in paused state, you should write your code in pauseApp() method.

And whenever you exit your application, it will transition from the ACTIVE or PAUSED state to a DESTROYED state. In destroyed state, all resources are de-allocated and the application process is killed. If you want to run some code at the exit time of your applicatin, like closing network connections and storage devices, you should write your code in destroyApp() method of your MIDlet class.

Following diagram gives a clear picture of the MIDlet lifecycle in J2ME applications.




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