1) componentWillReceiveProps is called before componentWillUpdate in React’s update lifecycle. You are right that componentWillReceiveProps allows you to call setState. On the other hand componentWillUpdate is a callback to use when you need to respond to a state change. The fundamental difference between props and state is that state is private to the component. That’s … Read more
No. Your entire application can be killed and recreated with the task stack intact; this lets the system reclaim memory on devices that need it while still presenting a seamless illusion of multitasking to the end user. From the docs: A background activity (an activity that is not visible to the user and has been … Read more
<div (window:beforeunload)=”doSomething()”></div> or @Component({ selector: ‘xxx’, host: {‘window:beforeunload’:’doSomething’} .. )} or @Component({ selector: ‘xxx’, .. )} class MyComponent { @HostListener(‘window:beforeunload’) doSomething() { } } This is how to listen to global events. I don’t know if the special behavior of this event is supported where the return value is used as text for the conformation … Read more
[UIApplication sharedApplication].applicationState will return current state of applications such as: UIApplicationStateActive UIApplicationStateInactive UIApplicationStateBackground or if you want to access via notification see UIApplicationDidBecomeActiveNotification Swift 3+ let state = UIApplication.shared.applicationState if state == .background || state == .inactive { // background } else if state == .active { // foreground } switch UIApplication.shared.applicationState { case .background, … Read more
If your view is static, then moving any code to the onActivityCreated method is not necessary. But when you – for instance, fill some lists from the adapter, then you should do it in the onActivityCreated method as well as restoring the view state when setRetainInstance used to do so. Also accessing the view hierarchy … Read more
It isn’t an official document, but this recently came up on Google+. The comments also have a good discussion with some detailed explanation.
onPause() is called when your activity is no longer at the top of the activity stack. A Dialog by itself is not an Activity, so will not replace the current Activity at the top of the stack, so will not cause anything to pause. A dialog (lower-case) does not need to be implemented by a … Read more
See also This post on Cocoanetics that present a very useful flowchart explaining the different calls to the AppDelegate methods during the app life cycle:
I still don’t understand why inactive activities that are on the stack don’t get reaped, and I’d really love to figure that out. This is not how things work. The only memory management that impacts activity lifecycle is the global memory across all processes, as Android decides that it is running low on memory and … Read more
Similar to activity lifecycle, Android calls onStart() when fragment becomes visible. onStop() is normally called when fragment becomes invisible, but it can also be called later in time. Depending on your layout Android can call onStart() even, when your Fragment is not yet visible, but it belongs to a visible parent container. For instance, this … Read more