Life cycle and loading process in iOS

Last Update:2015-05-15 Source: Internet

Author: User

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This section focuses on the life cycle of the application, the life cycle of the uiview, the exception handling process, and the loading process of the controller under the Uikit Framework. Four object diagrams Application life cycle The above process is explained:1. The program starts execution, first enters the main function:<pre name="code" class="objc"><pre name="code" class="objc">int main (int argc, char * argv[])</pre></pre> 2. Execute the Uiapplicationmain function:<pre name="code" class="objc"><pre name="code" class="objc">return uiapplicationmain (argc, argv, nil, nsstringfromclass ([hkappdelegate class]));</pre></pre> of the above function1th, the 2nd parameter is the system main function automatic processing parameter, does not do the Explanation.The 3rd Parameter: The class name of the application symbol (can only pass uiapplication or its subclasses, if nil, the default is Uiapplication)4th parameter: The class name of the UIApplication agent 3. Once the Uiapplicationmain method has finished executing, the uiapplication is initialized and the message loop mechanism is opened using its proxy. 4. The Agent listener event is a run loop that listens to the listed events until the program Exits. initialization process of the controllerDuring the application Life cycle, when the program is loaded, the<pre name="code" class="objc"><pre name="code" class="objc">-(BOOL) application: (uiapplication *) application didfinishlaunchingwithoptions: (nsdictionary *) launchOptions</pre></pre>method, You should complete the initialization of the root controller. The approximate code is as Follows:<pre name="code" class="objc"><pre name="code" class="objc">-(BOOL) application: (uiapplication *) application didfinishlaunchingwithoptions: (nsdictionary *) launchOptions { Self.window = [[uiwindow alloc] initwithframe:[[uiscreen mainscreen] bounds]]; Override point for customization after application Launch. Self.window.backgroundColor = [uicolor redcolor]; Self.viewcontroller = [[lfviewcontroller alloc] initwithnibname:@ "lfviewcontroller" bundle:nil]; Display Controller's view [self.window addSubview:self.viewController.view]; Set the Window's root controller self.window.rootViewController = self.viewcontroller; [self.window makekeyandvisible]; Return YES;}</pre></pre> 1. Be sure to do a strong reference to the defined Viewcontroller property, or the Lfviewcontroller object will be destroyed when the Didfinishlaunchingwithoptions method is Finished. <pre name="code" class="objc"><pre name="code" class="objc">@property (strong, Nonatomic) Lfviewcontroller *viewcontroller;</pre></pre> 2. Controller Lfviewcontroller Load specific process description:I. The view of the controller Lfviewcontroller is delayed-loadedII. when a view is used, the Controller's Loadview method is invoked to load the viewIii.loadview Loading View the default procedure ( Uiviewcontroller the default Implementation)1> if Nibname has a value, the corresponding xib file is loaded to create the view2> if Nibname has no value1) first load the Lfview.xib file to create the view2) load the Lfviewcontroller.xib file to create the view3) If you do not find the Xib file described above, you will create a black view with the code Page life cycle In the flow chart of the page life cycle, when viewdiddisappear, there is a possibility of low memory situation, will call the Viewdidunload method for memory warning processing work, the flowchart is as Follows: Life cycle and loading process in iOS

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Life cycle and loading process in iOS

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