Android do every second

Android Retrofit Call Every X Seconds

Android Tutorial

In this tutorial, we’ll be implementing RxJava with Retrofit such that the Retrofit Service is called every x seconds in our Android Application.

Android RxJava and Retrofit

We have already discussed the basics of RxJava and Retrofit together, here.

In order to create a Retrofit service that runs after certain time intervals, we can use the following :

Handlers are used to communicate/pass data from the background thread to the UI thread

Using RxJava we can do much more than that and very easily as well, using RxJava operators.
We can use the interval operator to call a certain method ( retrofit network call in our case) after every given period.

Observable.interval operator is used to emit values after certain intervals. It looks like this:

1000 is the initial delay before the emission starts and repeats every 5 seconds.

We can subscribe our observers which would call the Retrofit method after every 5 seconds.

Calling Retrofit service after certain intervals is fairly common in applications that provide live updates, such as Cricket Score application etc.

Let’s get started with our implementation in the following section. We’ll be creating an application which shows a new random joke in the TextView after every 5 seconds.

Project Structure

Add the following dependencies to the build.gradle file:

In order to use lambda syntax, make sure that the compile options are set as the following inside the android block in the build.gradle.

The code for the activity_main.xml layout is given below:

Create an APIService.java class where the API is defined:

Following is the POJO model for the Jokes.java class :

The code for the MainActivity.java is given below:

setLenient() is used to prevent Misinformed JSON response exceptions.

The disposable instance is unsubscribed when the user leaves the activity.

Check the isDisposed method on the Disposable before creating the Observable stream again in the onResume method.

The output of the application in action is given below:

That brings an end to this tutorial. You can download the project from the link below:

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Android Application Launch explained: from Zygote to your Activity.onCreate()

Apr 30, 2018 · 6 min read

This article explains how Android launches your application when a user clicks an app icon. The Android system does a lot of heavy lifting behind the curtains to make your launch activity visible to a user. This article covers this process in detail by highlighting the important phases and call sequences.

Android applications are unique in two ways:

1. Multiple Entry points: Android apps are composed of different components and they can invoke the components owned by other apps. These components roughly correspond to multiple entry points for any application. Hence, they differ from traditional applications which have a single entry point like main() method.
2. Own Little World: Every Android application lives in its own world, it runs in a separate process, it has its own Dalvik VM instance and is assigned a unique user ID.

When does Android process start?

An Android process is started whenever it is required.

Any time a user or some other sys t em component requests a component (could be a service, an activity or an intent receiver) that belongs to your application be executed, the Android system spins off a new process for your app if it’s not already running. Generally processes keep running until killed by the system. Application processes are created on demand and a lot of things happen before you see your application’s launch activity up and running.

Every app runs in its own process: By default, every Android app runs in its own Android process which is nothing but a Linux process which gets one execution thread to start with. For example, when you click on a hyper-link in your e-mail, a web page opens in a browser window. Your mail client and the browser are two separate apps and they run in their two separate individual processes. The click event causes Android platform to launch a new process so that it can instantiate the browser activity in the context of its own process. The same holds good for any other component in an application.

Zygote : Spawning new life, new process

Let’s step back for a moment and have a quick look on system start-up process. Like the most Linux based systems, at startup, the boot loader loads the kernel and starts the init process. The init then spawns the low level Linux processes called “daemons” e.g. android debug daemon, USB daemon etc. These daemons typically handle the low level hardware interfaces including radio interface.

Init process then starts a very interesting process called ‘ Zygote ’.

As the name implies it’s the very beginning for the rest of the Android application. This is the process which initializes a very first instance of Dalvik virtual machine. It also pre-loads all common classes used by Android application framework and various apps installed on a system. It thus prepares itself to be replicated. It stats listening on a socket interface for future requests to spawn off new virtual machines (VM)for managing new application processes. On receiving a new request, it forks itself to create a new process which gets a pre-initialized VM instance.

After zygote, init starts the runtime process.

The zygote then forks to start a well managed process called system server. System server starts all core platform services e.g activity manager service and hardware services in its own context.

At this point the full stack is ready to launch the first app process — Home app which displays the home screen also known as Launcher application.

When a user clicks an app icon in Launcher …

The click event gets translated into startActivity(intent) and it is routed to ActivityManagerService via Binder IPC. The ActvityManagerService performs multiple steps

1. The first step is to collect information about the target of the intent object. This is done by using resolveIntent() method on PackageManager object. PackageManager.MATCH_DEFAULT_ONLY and PackageManager.GET_SHARED_LIBRARY_FILES flags are used by default.
2. The target information is saved back into the intent object to avoid re-doing this step.
3. Next important step is to check if user has enough privileges to invoke the target component of the intent. This is done by calling grantUriPermissionLocked() method.
4. If user has enough permissions, ActivityManagerService checks if the target activity requires to be launched in a new task. The task creation depends on Intent flags such as FLAG_ACTIVITY_NEW_TASK and other flags such as FLAG_ACTIVITY_CLEAR_TOP.
5. Now, it’s the time to check if the ProcessRecord already exists for the process.If the ProcessRecord is null, the ActivityManager has to create a new process to instantiate the target component.

As you saw above many things happen behind the scene when a user clicks on an icon and a new application gets launched. Here is the full picture :

There are three distinct phases of process launch :

1. Process Creation
2. Binding Application
3. Launching Activity / Starting Service / Invoking intent receiver …

ActivityManagerService creates a new process by invoking startProcessLocked() method which sends arguments to Zygote process over the socket connection. Zygote forks itself and calls ZygoteInit.main() which then instantiates ActivityThread object and returns a process id of a newly created process.

Every process gets one thread by default. The main thread has a Looper instance to handle messages from a message queue and it calls Looper.loop() in its every iteration of run() method. It’s the job of a Looper to pop off the messages from message queue and invoke the corresponding methods to handle them. ActivityThread then starts the message loop by calling Looper.prepareLoop() and Looper.loop() subsequently.

The following sequence captures the call sequence in detail —

The next step is to attach this newly created process to a specific application. This is done by calling bindApplication() on the thread object. This method sends BIND_APPLICATION message to the message queue. This message is retrieved by the Handler object which then invokes handleMessage() method to trigger the message specific action — handleBindApplication(). This method invokes makeApplication() method which loads app specific classes into memory.

This call sequence is depicted in following figure.

Launching an Activity:

After the previous step, the system contains the process responsible for the application with application classes loaded in process’s private memory. The call sequence to launch an activity is common between a newly created process and an existing process.

The actual process of launching starts in realStartActivity() method which calls sheduleLaunchActivity() on the application thread object. This method sends LAUNCH_ACTIVITY message to the message queue. The message is handled by handleLaunchActivity() method as shown below.

Assuming that user clicks on Video Browser application. the call sequence to launch the activity is as shown in the figure.

The Activity starts its managed lifecycle with onCreate() method call. The activity comes to foreground with onRestart() call and starts interacting with the user with onStart() call.

Thanks for reading through 🙌🏼. If you found this post useful, please applaud using the 👏 button and share it through your circles.

This article was initially published as two part series (Part 1 and Part 2) on my blog ./ mult-core-dump in 2010. These articles have been cited in multiple documents including the very famous Introduction to the Android Graphics Pipeline

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Android 12

More personal, safe and effortless than ever before.

Android 12 delivers even more personal, safe and effortless experiences on your device. Featuring a totally reimagined UI just for you, new privacy features that are designed for your safety and put you in control, and more seamless ways to get right to your gameplay or even switch to a new device.

Android 12 delivers even more personal, safe and effortless experiences on your device. Featuring a totally reimagined UI just for you, new privacy features that are designed for your safety and put you in control, and more seamless ways to get right to your gameplay or even switch to a new device.

Android 12
Highlights

PERSONAL

Our most personal OS yet.

Android 12 is our most personal OS ever, featuring dynamic color capabilities that can transform your experience based on your wallpaper and responsive motion that responds to your touch. Even the widgets have been given a facelift, with your favorite people always available right there on your home screen. And with a more spacious redesign, color contrast optimizations and new features to help those with low vision, Android 12 is designed to be accessible for even more users.

MATERIAL YOU

A boundary-pushing redesign.

Android 12 rethinks the entire user interface, from shapes, light and motion, to customizable system colors that can be adapted to match you. Redesigned to be more spacious and comfortable, it’s our most expressive, dynamic and personal OS ever.

DYNAMIC COLOR

Color reimagined.

Change your wallpaper on your Pixel and your entire Android 12 experience changes to match. Using advanced color extraction algorithms you can easily personalize the look and feel of your entire phone, including notifications, settings, widgets and even select apps.

RESPONSIVE MOTION

A smoother, more responsive UI.

The UI feels alive with every tap, swipe and scroll—responding quickly and expressively with smooth motion and animations. Android 12 delivers improved system performance so your device can work in perfect harmony with you.

A phone displaying the new Android 12 UI.

The UI feels alive with every tap, swipe and scroll—responding quickly and expressively with smooth motion and animations. Android 12 delivers improved system performance so your device can work in perfect harmony with you.

CONVERSATION WIDGETS

Your favorite people have a new home.

An all-new conversation widget puts the conversations with the people you care about front-and-center on your home screen so you never miss a chat from your loved ones. You can even see missed calls, birthdays and more at a glance.

An all-new conversation widget puts the conversations with the people you care about front-and-center on your home screen so you never miss a chat from your loved ones. You can even see missed calls, birthdays and more at a glance.

ACCESSIBILITY IMPROVEMENTS

Built for accessibility.

Android 12 is designed to be even more accessible with new visibility features, including:

Area magnification

A new window magnifier lets you zoom in on a part of your screen without having to lose context on the rest of the screen content.

A phone displaying the new Android 12 extra dim feature.

Extra dim

Make your display extra dim for night-time scrolling or situations when even the lowest brightness setting is too bright.

A phone displaying the new Android 12 bold text feature.

Bold text

See text more clearly with the ability to switch the font to bold across the whole phone.

A phone displaying the new Android 12 grayscale feature.

Grayscale

Adjust how colors display on your device to grayscale.

Private by design so you’re in control.

Android 12 is designed for your safety. With new easy-to-use, powerful privacy features, you’ll have peace of mind knowing that you have control over who can see your data and when.

MIC & CAMERA INDICATORS AND TOGGLES

Stronger mic and camera access controls.

With Android 12, you can see when an app is using your microphone or camera thanks to a new indicator in your phone’s status bar. And if you don’t want any apps to access your microphone or camera, you can completely disable those sensors using two new toggles in quick settings. Simply flip the switch.

A phone displaying the Android 12 camera. Bubbles in the foreground read “Camera access: Available” and “Mic access: Blocked.”

With Android 12, you can see when an app is using your microphone or camera thanks to a new indicator in your phone’s status bar. And if you don’t want any apps to access your microphone or camera, you can completely disable those sensors using two new toggles in quick settings. Simply flip the switch.

APPROXIMATE LOCATION PERMISSIONS

Keep your precise location private.

While some apps need precise location information for tasks like turn-by-turn navigation, many other apps only need your approximate location to be helpful. With Android 12, you can choose between giving apps access to your precise location or an approximate location instead.

A phone displaying the new Android 12 Approximate Location Permissions Screen. The screen reads: “Allow [App] to access this device’s location?” with “Approximate” location selected.

While some apps need precise location information for tasks like turn-by-turn navigation, many other apps only need your approximate location to be helpful. With Android 12, you can choose between giving apps access to your precise location or an approximate location instead.

PRIVACY DASHBOARD

Your privacy permissions at a glance.

Privacy dashboard gives you a clear and comprehensive view of when apps access your location, camera or mic over the past 24 hours. If you see anything that you’re not comfortable with, you can manage permissions right from the dashboard.

A phone displaying the new Android 12 privacy dashboard.

Privacy dashboard gives you a clear and comprehensive view of when apps access your location, camera or mic over the past 24 hours. If you see anything that you’re not comfortable with, you can manage permissions right from the dashboard.

PRIVATE COMPUTE CORE

Protect sensitive data in the Private Compute Core.

Powerful Android features like Live Caption and Now Playing are enabled by continuous streams of data like audio from your apps, sounds nearby, or the content on your screen. But this data can be highly sensitive and you might not want it to leave your phone.

It’s essential that we build these features in a privacy-preserving way, so we built Private Compute Core. It’s a first-of-its-kind secure mobile environment that is isolated from the rest of the operating system and your apps. Any information processed in Private Compute Core requires explicit user action before it can be shared with Google or any app or service. And like the rest of Android, the protections in Private Compute Core are open source and fully inspectable and verifiable by the security community.

Powerful Android features like Live Caption and Now Playing are enabled by continuous streams of data like audio from your apps, sounds nearby, or the content on your screen. But this data can be highly sensitive and you might not want it to leave your phone.

It’s essential that we build these features in a privacy-preserving way, so we built Private Compute Core. It’s a first-of-its-kind secure mobile environment that is isolated from the rest of the operating system and your apps. Any information processed in Private Compute Core requires explicit user action before it can be shared with Google or any app or service. And like the rest of Android, the protections in Private Compute Core are open source and fully inspectable and verifiable by the security community.

EFFORTLESS

Everything on your phone just got easier.

Android 12 makes everything on your phone effortless and easy. You can get into gameplay without having to wait for a full download and even transfer your data onto a new Android phone without any hassle.

ENHANCED GAMING

Kick-start your gameplay.

Spend less time waiting and more time playing. Android 12 lets you play as you download, so you can jump straight into gameplay without needing to wait for the full download to finish. 1

You can also select your game mode for performance or battery life, whether you want a richer gaming experience or longer play session.

Two phones running Android 12. The first screen shows the Google Play page for Touchgrind BMX, with the game mid-download. The second screen shows the loading screen for the game.

Spend less time waiting and more time playing. Android 12 lets you play as you download, so you can jump straight into gameplay without needing to wait for the full download to finish. 1

You can also select your game mode for performance or battery life, whether you want a richer gaming experience or longer play session.

SCROLLING SCREENSHOTS

Extend screenshots beyond your screen.

Just because you reach the end of your screen doesn’t mean you need to reach the end of your screenshot. Scrolling screenshots allow you to capture all the content on the page in one image.

A phone displaying the new Android 12 scrolling screenshots feature.

Just because you reach the end of your screen doesn’t mean you need to reach the end of your screenshot. Scrolling screenshots allow you to capture all the content on the page in one image.

EASILY SWITCH PHONES

Switching made easy.

It’s never been easier to switch to Android and try out the best device for you. Starting on Android 12, you can transfer all your essentials by connecting your old phone to your new Android with a cable or shared WiFi connection. Your memories and data will transfer, stress-free—even from iPhone® (welcome!).

It’s never been easier to switch to Android and try out the best device for you. Starting on Android 12, you can transfer all your essentials by connecting your old phone to your new Android with a cable or shared WiFi connection. Your memories and data will transfer, stress-free—even from iPhone® (welcome!).

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