如何判断iOS应用程序是否从快速应用程序切换或手动进入前台？

Question

Is there a way to tell if an iOS app enters the foreground from fast-app switching or manually? I need to know by the time applicationWillEnterForeground is called, so some specific code can be executed (or not executed) depending on the condition in which the app entered the foreground.

EDIT: It turned out that this was more of a design issue for me. I moved my code to applicationDidBecomeActive. I also added a BOOL property to the appDelegate called fastAppSwitching (probably the wrong name for it). I set this to YES in application:handleOpenURL and application:openURL:sourceApplication:annotation. Then I added the following code to application:didFinishLaunchingWithOptions:

        if (launchOptions) {
            self.fastAppSwitching = YES;
        }
        else {
            self.fastAppSwitching = NO;
        }

In applicationDidBecomeActive, I used the following code:

    if (fastAppSwitching == YES) {
        self.fastAppSwitching = NO; //stop, don't go any further
    }
    else {
       ...
    }

EDIT2: MaxGabriel makes a good point below: "Just a warning to others taking the solution described here, applicationDidBecomeActive: is called when the user eg ignores a phone call or text message, unlike applicationWillEnterForeground". This is actually also true for in-app purchases and Facebook in-app authorization (new in iOS 6). So, with some further testing, this is the current solution:

Add a new Bool called passedThroughWillEnterForeground.

In applicationWillResignActive:

self.passedThroughWillEnterForeground = NO;

In applicationDidEnterBackground:

self.passedThroughWillEnterForeground = NO;

In applicationWillEnterForeground:

self.passedThroughWillEnterForeground = YES;

In applicationDidBecomeActive:

    if (passedThroughWillEnterForeground) {
        //we are NOT returning from 6.0 (in-app) authorization dialog or in-app purchase dialog, etc
        //do nothing with this BOOL - just reset it
        self.passedThroughWillEnterForeground = NO;
    }
    else {
        //we ARE returning from 6.0 (in-app) authorization dialog or in-app purchase dialog - IE
        //This is the same as fast-app switching in our book, so let's keep it simple and use this to set that
        self.fastAppSwitching = YES;
    }

    if (fastAppSwitching == YES) {

        self.fastAppSwitching = NO;
    }
    else {
        ...
    }

EDIT3: I think we also need a bool to tell if app was launched from terminated.

Answer 1

If your application is launched by another application, the

- (BOOL)application:(UIApplication *)app
            openURL:(NSURL *)url
  sourceApplicarion:(NSString *)bundleID
         annotation:(id)info;

method is called on your app delegate. You can use this method to eg set a Boolean switch to true that indicates whether the app was launched by another program.

The peoblem is that this method is called after applicationWillEnterForeground: , so you can't tell in that method whether your app was launched manually or automatically.

However, I suspect that if you need this to be detected in a particular method, you may have a design problem and you should probably reorganize your code.

Answer 2

如果您的应用程序是从其他应用application:openURL:sourceApplication:annotation打开的，则application:openURL:sourceApplication:annotation将在您的应用程序委托上调用application:openURL:sourceApplication:annotation 。