{"id":530,"date":"2016-09-22T12:35:10","date_gmt":"2016-09-22T05:35:10","guid":{"rendered":"http:\/\/www.lixsu.xyz\/?p=530"},"modified":"2016-09-22T12:35:10","modified_gmt":"2016-09-22T05:35:10","slug":"android-activity-lifecycle","status":"publish","type":"post","link":"https:\/\/lixionary.com\/index.php\/2016\/09\/22\/android-activity-lifecycle\/","title":{"rendered":"Android Activity Lifecycle"},"content":{"rendered":"

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Willing to develop your own apps? Here i will bring you some basics about it. For me, the most basic thing before doing an android apps is\u00a0knowing how the screen can be populated with fancy UI like in whatsapp, facebook, etc and destroy it.<\/p>\n

Android will do couple of actions from you pressed your apps icon till it’s\u00a0closed again by\u00a0pressing\u00a0back or home. In android apps,\u00a0screen content will be managed by Activity class or its subclass like AppCompatActivity. Android Application can be consisted of more than one activity. Each activity will isolate its state and data from others except you shared them in Application Context. Everything inside application context can be shared between activities in same context (but there’s a better way to do this by using intent).<\/p>\n

\"screenshot_20160922-115531\"\"screenshot_20160922-115535\"<\/p>\n

As described above, everything that shown in user’s screen will depends on activity class, so let’s figure it out how android manage the UI from activity. The one activity’s basic is to know its lifecycle. Activity\u00a0entered its life the same time it need to shown to the screen and destroyed when it removed from screen. As described here<\/a>, activities will have at least 4 essential state, but here i will provide you more than it because without fully knowing it’s state, I doubt that you can create a stable apps that give a good UX. Basic flow of android lifecycle can be seen in figure below.<\/p>\n

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\"activity_lifecycle\"<\/p>\n

    \n
  1. onCreate()<\/li>\n
  2. onStart()<\/li>\n
  3. onResume()<\/li>\n
  4. onPause()<\/li>\n
  5. onStop()<\/li>\n
  6. onDestroy()<\/li>\n
  7. onRestart()<\/li>\n
  8. onSaveInstanceState()<\/li>\n
  9. onRestoreInstanceState()<\/li>\n<\/ol>\n

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     <\/p>\n

    Then, how to trace back the state of our activity? The easiest way might be by use Log inside every state callback inside your activity like :<\/p>\n

    \n    @Override\n    protected void onRestart() {\n        Log.i(TAG, \"entering on restart\");\n        super.onRestart();\n    }\n\n    @Override\n    protected void onStart() {\n        Log.i(TAG, \"entering on start\");\n        super.onStart();\n    }\n<\/code><\/pre>\n
    Here i provide you with 4 scenarios :<\/p>\n