ios 四新特性多任务

ios 4 新特性多任务

一：了解multitasking

??????? background apps(可以在后台运行的任务):

???????????? 1:play audio?

??????????? ?2:get location

???????????? 3:voip stream

???????????? 4:request time to finish

???????????? 5: create notifications

二：多任务生命周期

1：程序加载成功

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions

2：程序将要失去活跃状态

- (void)applicationWillResignActive:(UIApplication *)application

3：程序已经进入后台运行

- (void)applicationDidEnterBackground:(UIApplication *)application

4：程序将要进入前台运行

- (void)applicationWillEnterForeground:(UIApplication *)application

5：程序进入活跃状态

- (void)applicationDidBecomeActive:(UIApplication *)application

6：程序退出

- (void)applicationWillTerminate:(UIApplication *)application

从启动到转入后台，从后台转入前台，退出，生命周期函数调用顺序

1->5->2->3->4->5->6

三：转入后台后请求一段时间完成操作

UIBackgroundTaskIdentifier backgroundTask; - (void)applicationDidEnterBackground:(UIApplication *)application {   // tell the OS you're about to begin a background task that may need time to finish    backgroundTask = [application beginBackgroundTaskWithExpirationHandler: ^{        // 如果超时这个block将被调用        dispatch_async(dispatch_get_main_queue(), ^{            if (backgroundTask != UIBackgroundTaskInvalid)            {    // do whatever needs to be done                [application endBackgroundTask:backgroundTask];                backgroundTask = UIBackgroundTaskInvalid;            }        });    }];       // Start the long-running task    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{          // Do the work!  [NSThread sleepForTimeInterval:5];  NSLog(@"Time remaining: %f",[application backgroundTimeRemaining]);  [NSThread sleepForTimeInterval:5];  NSLog(@"Time remaining: %f",[application backgroundTimeRemaining]);      [NSThread sleepForTimeInterval:5];  NSLog(@"Time remaining: %f",[application backgroundTimeRemaining]);  // done!            // call endBackgroundTask - should be executed back on  // main thread        dispatch_async(dispatch_get_main_queue(), ^{            if (backgroundTask != UIBackgroundTaskInvalid)            {    // if you don't call endBackgroundTask, the OS will exit your app.                [application endBackgroundTask:backgroundTask];                backgroundTask = UIBackgroundTaskInvalid;            }        });    }); NSLog(@"Reached the end of ApplicationDidEnterBackground - I'm done!"); }

四：本地消息

1：创建一个本地消息

-(IBAction) scheduleNotification {    UILocalNotification *local = [[UILocalNotification alloc] init];     // create date/time information local.fireDate = [NSDate dateWithTimeIntervalSinceNow:15];    local.timeZone = [NSTimeZone defaultTimeZone];  // set notification details    local.alertBody = @"Missing you already!";    local.alertAction = @"View";  // set the badge on the app icon    local.applicationIconBadgeNumber = 1;  // Gather any custom data you need to save with the notification    NSDictionary *customInfo =  [NSDictionary dictionaryWithObject:@"ABCD1234" forKey:@"yourKey"];    local.userInfo = customInfo;  // Schedule it!    [[UIApplication sharedApplication] scheduleLocalNotification:local];     [local release];}

2：delegate 处理方法

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {            // Override point for customization after application launch.    // Add the view controller's view to the window and display.    [window addSubview:viewController.view];    [window makeKeyAndVisible];  //程序启动是检查是否有UILocalNotification，如果有跳出提示框// reset badge  application.applicationIconBadgeNumber = 0;     // If the app was closed, and we launched from the notification    UILocalNotification *local =    [launchOptions objectForKey:UIApplicationLaunchOptionsLocalNotificationKey];    if (local) {        UIAlertView *alert = [[UIAlertView alloc]         initWithTitle:@"You came back! (App was closed)"       message:@"Nice to see you again!" delegate:nil       cancelButtonTitle:@"Okay" otherButtonTitles:nil];  [alert show];  [alert release];    }  return YES;}

//如果程序完全退出，此方法不会被调用，而是先调用didFinishLaunchingWithOptions把程序启动起来。如果该程序在后台运行收到消息时直接调用该方法- (void)application:(UIApplication *)application didReceiveLocalNotification:(UILocalNotification *)local { // reset badge number application.applicationIconBadgeNumber = 0;   if (local) {  // get custom info from dictionary  NSString *customInfo = [local.userInfo objectForKey:@"yourKey"];  //         UIAlertView *alert = [[UIAlertView alloc]         initWithTitle:@"You came back! (App was running)"         message:customInfo delegate:nil         cancelButtonTitle:@"Okay" otherButtonTitles:nil];  [alert show];  [alert release];    }}

五：后台播放音乐

1：读取文件

- (void)viewDidLoad {    [super viewDidLoad];  self.playPauseButton.titleLabel.text == @"play";  // grab the path to the caf file NSString *soundFilePath = [[NSBundle mainBundle] pathForResource: @"Rainstorm"         ofType: @"mp3"];  NSURL *fileURL = [[NSURL alloc] initFileURLWithPath: soundFilePath];  // create a new AVAudioPlayer initialized with the URL to the file AVAudioPlayer *newPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL: fileURL             error: nil]; [fileURL release];  // set our ivar equal to the new player self.player = newPlayer; [newPlayer release];  // preloads buffers, gets ready to play [player prepareToPlay];  // set delegate so we can get called back when the sound has finished playing [player setDelegate: self];   //重要的两行  // set category of audio [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayback error:nil]; // announce that we want to hook up to remote UI events [[UIApplication sharedApplication] beginReceivingRemoteControlEvents]; }

2：重写canBecomeFirstResponder 方法，使改view 可以成为第一响应者

-(BOOL) canBecomeFirstResponder {       return YES;}

?3：显示view时，设置为第一响应者

-(void) viewDidAppear:(BOOL)animated {       [self becomeFirstResponder];}

4：实现remoteControlReceivedWithEvent方法使程序接收 iphone 自动音乐控制事件

-(void) remoteControlReceivedWithEvent:(UIEvent *)event { switch (event.subtype) {       case UIEventSubtypeRemoteControlTogglePlayPause:                [self playPause];       default:       break;     }}

?5：info.plist 设置，可以设置多种形式

 &lt;key&gt;UIBackgroundModes&lt;/key&gt; &lt;array&gt;  &lt;string&gt;audio&lt;/string&gt; &lt;/array&gt;

?六：NSUserDefaults? 问题

如果程序在后台挂起，在转入到前台后不会调用viewDidLoad 方法，所以要在viewDidLoad 方法里面注册UIApplicationWillEnterForegroundNotification ，调用loadSettings

-(void) loadSettings: (NSNotification *) notification {         NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];         [defaults synchronize];  }

// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.- (void)viewDidLoad {  [self loadSettings:nil];  NSNotificationCenter *notificationCenter = [NSNotificationCenter defaultCenter]; [notificationCenter addObserver:self       selector:@selector(loadSettings:)       name:UIApplicationWillEnterForegroundNotification         object:nil];     [super viewDidLoad];}

七：去除后台运行inof.list

application dose not run in background?? 设置为 ?true

ios 四 新特性 多任务

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ios 四新特性多任务