oncreate

问题 I have created an Android Application Project and in MainActivity.java > onCreate() it is calling super.onCreate(savedInstanceState) . As a beginner, can anyone explain what is the purpose of the above line? 回答1: Every Activity you make is started through a sequence of method calls. onCreate() is the first of these calls. Each and every one of your Activities extends android.app.Activity either directly or by subclassing another subclass of Activity . In Java, when you inherit from a class,

问题 This question already has answers here : Closed 7 years ago . Possible Duplicate: Android Activity Life Cycle - difference between onPause() and OnStop() I was wondering - what is the difference between onCreate() and onStart() methods? I think that onStart() is a redundant method. onCreate() will ALWAYS be called (At least in my last two projects). Can any one explain the difference? 回答1: Take a look on life cycle of Activity Where ***onCreate()*** Called when the activity is first created.

问题 What are the differences between onCreate() , onCreateView() , and onActivityCreated() in fragments and what would they each be used for? 回答1: onCreate(): The onCreate() method in a Fragment is called after the Activity 's onAttachFragment() but before that Fragment 's onCreateView() . In this method, you can assign variables, get Intent extras, and anything else that doesn't involve the View hierarchy (i.e. non-graphical initialisations). This is because this method can be called when the

问题 What is the life cycle of an Android activity? Why are so many similar sounding methods ( onCreate() , onStart() , onResume() ) called during initialization, and so many others ( onPause() , onStop() , onDestroy() ) called at the end? When are these methods called, and how should they be used properly? 回答1: See it in Activity Lifecycle (at Android Developers). onCreate() : Called when the activity is first created. This is where you should do all of your normal static set up: create views,

问题 Can anyone help me to find out what can be the issue with this program. In the onCreate() method the findViewById() returns null for all ids and this causes a null pointer exception later. I can not figure out why the findViewById() can not find the view. Any suggestions? This is the main code: public class MainActivity extends Activity { ViewPager pager; MyPagerAdapter adapter; LinearLayout layout1, layout2, layout3; @Override protected void onCreate(Bundle savedInstanceState) { super