Tutorial by Examples: n

As your activity begins to stop, the system calls onSaveInstanceState() so your activity can save state information with a collection of key-value pairs. The default implementation of this method automatically saves information about the state of the activity's view hierarchy, such as the text in an...

Fragments also have a onSaveInstanceState() method which is called when their state needs to be saved: public class MySimpleFragment extends Fragment { private int someStateValue; private final String SOME_VALUE_KEY = "someValueToSave"; // Fires when a configuration ch...

In many cases, we can avoid problems when an Activity is re-created by simply using fragments. If your views and state are within a fragment, we can easily have the fragment be retained when the activity is re-created: public class RetainedFragment extends Fragment { // data object we want to ...

If you want to lock the screen orientation change of any screen (activity) of your android application you just need to set the android:screenOrientation property of an <activity> within the AndroidManifest.xml: <activity android:name="com.techblogon.screenorientationexample.Main...

If your application doesn't need to update resources during a specific configuration change and you have a performance limitation that requires you to avoid the activity restart, then you can declare that your activity handles the configuration change itself, which prevents the system from restartin...

- (UIImage *)getSnapshot { UIScreen *screen = [UIScreen mainScreen]; CGRect bounds = [self.view bounds]; UIGraphicsBeginImageContextWithOptions(bounds.size, false, screen.scale); CGContextRef context = UIGraphicsGetCurrentContext(); CGContextSetInterpolationQuality(context, kCGInterpola...

The CAEmitterLayer class provides a particle emitter system for Core Animation. The particles are defined by instances of CAEmitterCell. The particles are drawn above the layer’s background color and border. var emitter = CAEmitterLayer() emitter.emitterPosition = CGPoin...

Demonstrate how to embed a lua interpreter in C code, expose a C-defined function to Lua script, evaluate a Lua script, call a C-defined function from Lua, and call a Lua-defined function from C (the host). In this example, we want the mood to be set by a Lua script. Here is mood.lua: -- Get versi...

To setup a WebRTC-based communication system, you need three main components: A WebRTC signaling server To establish a WebRTC connections, peers need to contact a signaling server, which then provides the address information the peers require to set up a peer-to-peer connection. Signaling serv...

Suppose you have multiple threads running. Each thread is doing one task. You want to get notified either on the mainThread OR another thread, when all the task-threads are completed. The simplest solution to such a problem is a DispatchGroup. When using a DispatchGroup, for each request, you ente...

Validation attributes can be used to easily configure model validation. public class MyModel { public int id { get; set; } //sets the FirstName to be required, and no longer than 100 characters [Required] [StringLength(100)] public string FirstName { get; set; } } Th...

Basics There are a number of different transforms you can do on a layer, but the basic ones are translate (move) scale rotate To do transforms on a CALayer, you set the layer's transform property to a CATransform3D type. For example, to translate a layer, you would do something like this:...

CALayer property animations are enabled by default. When this is undesirable, they can be disabled as follows. Swift CATransaction.begin() CATransaction.setDisableActions(true) // change layer properties that you don't want to animate CATransaction.commit() Objective-C [CATransaction be...

You can test that a function throws an exception with the built-in unittest through two different methods. Using a context manager def division_function(dividend, divisor): return dividend / divisor class MyTestCase(unittest.TestCase): def test_using_context_manager(self): ...

Xposed is a framework that allows you to hook method calls of other apps. When you do a modification by decompiling an APK, you can insert/change commands directly wherever you want. However, you will need to recompile/sign the APK afterwards and you can only distribute the whole package. With Xpose...

Create a new class implementing IXposedHookLoadPackage and implement the handleLoadPackage method: public class MultiPatcher implements IXposedHookLoadPackage { @Override public void handleLoadPackage(XC_LoadPackage.LoadPackageParam loadPackageParam) throws Throwable { ...

In an iOS app, your user interface can take on one of a few different general shapes and sizes. These are defined using size classes, which are available through a view or view controller's trait collection. Apple defines two size classes: regular and compact. Each of these size classes are availab...

Making an app adaptive – that is, responding to size class changes by changing your layout – often involves lots of help from the Auto Layout system. One of the primary ways apps become adaptive is by updating the active Auto Layout constraints when a view's size class changes. For example, conside...

A key piece of adaptivity in a modern iOS app is supporting multitasking on iPad. By default, apps created in Xcode 7 and newer will be configured to support multitasking: they'll have a LaunchScreen.storyboard file that uses Auto Layout. The easiest way for existing apps to opt in to multitasking ...

String literals are used to specify arrays of characters. They are sequences of characters enclosed within double quotes (e.g. "abcd" and have the type char*). The L prefix makes the literal a wide character array, of type wchar_t*. For example, L"abcd". Since C11, there are ot...