Android start activity from browser

[Android]Start Activity by Custom URL Scheme

If you want start activity, you write code like this.

And If you want launch url page, you will pass Uri with Intent.ACTION_VIEW.

If you use many browser in your phone, android will show select browser view for url load.
This select view is not only url also any other duplication action.

How you can see this select view?

Because that applications use same custom scheme (like ‘http://’, ‘xxx://’)

Let’s see example.
This is notification view about user’s action.
(Look like facebook or instagram’s notification view)

If you click item of list, we will move to activity.
Post’s row id is 10 and Activity name is ‘Activity_Post_Detail’.
Then you can write code like this.
Make new intent instance and pass String extra.

But If you use ‘Custom URL’, you can write code like this.
(Look like load url page)

This way don’t need Activity name. (need only url path)
Furthermore you can launch activity at your browser

Custom URL Scheme

1. Declare host / scheme at your activity (AndroidManifest.xml)

In this example, schme is selphone and host is post_detail

(Custom url will selphone://post_detail)

Now If you load ‘selphone://post_detail?…’ url, this activity will launch.

2. If you want to pass parameter to Activity, pass by query string

If you want pass post_id ( id: 10), you can add query string end of url.
“selphone://post_detail?post_id=10”

3. In your Activity, get your parameter at query string

Check intent action, and get query parameter from intent data.

Do it your self custom url activity for your application
If you want to know more detail infomation, check this page Android Intent Fileters

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Android Intents with Chrome

Published on Friday, February 28, 2014

A little known feature in Android lets you launch apps directly from a web page via an Android Intent. One scenario is launching an app when the user lands on a page, which you can achieve by embedding an iframe in the page with a custom URI-scheme set as the src , as follows: . This works in the Chrome for Android browser, version 18 and earlier. It also works in the Android browser, of course.

The functionality has changed slightly in Chrome for Android, versions 25 and later. It is no longer possible to launch an Android app by setting an iframe’s src attribute. For example, navigating an iframe to a URI with a custom scheme such as paulsawesomeapp:// will not work even if the user has the appropriate app installed. Instead, you should implement a user gesture to launch the app via a custom scheme, or use the «intent:» syntax described in this article.

# Syntax

The best practice is to construct an intent anchor and embed that into the page so the user can launch the app. This gives you a lot more flexibility in controlling how apps are launched, including the ability to pass extra information into the app via Intent Extras.

The basic syntax for an intent-based URI is as follows:

See the Android source for parsing details.

Also, you may choose to specify fallback URL by adding the following string extra:

When an intent could not be resolved, or an external application could not be launched, then the user will be redirected to the fallback URL if it was given.

Some example cases where Chrome does not launch an external application are as follows:

• The intent could not be resolved, i.e., no app can handle the intent.
• JavaScript timer tried to open an application without user gesture.

Note that S. is a way to define string extras. S.browser_fallback_url was chosen for backward compatibility, but the target app won’t see browser_fallback_url value as Chrome removes it.

# Examples

Here’s an intent that launches the Zxing barcode scanner app. It follows the syntax thus:

To launch the Zxing barcode scanner app, you encode your href on the anchor as follows:

See the Android Zxing Manifest, which defines the package and the host.

Also, if fallback URL is specified, the full URL will look like this:

Now the URL will get you to zxing.org if the app could not be found, or the link was triggered from JavaScript without user gesture (or for other cases where we don’t launch an external application.)

# Considerations

If the activity you invoke via an intent contains extras, you can include these as well.

Only activities that have the category filter, android.intent.category.BROWSABLE are able to be invoked using this method as it indicates that the application is safe to open from the Browser.

# See also

And Chrome doesn’t launch an external app for a given Intent URI in the following cases.

• When the Intent URI is redirected from a typed in URL.
• When the Intent URI is initiated without user gesture.

Last updated: Friday, February 28, 2014 • Improve article

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Make a link in the Android browser start up my app?

Is it possible to make a link such as:

cause my Anton app to start up?

I know that this works for the Android Market app with the market protocol, but can something similar be done with other apps?

Here is an example of a link that will start up the Android Market:

Update: The answer I accepted provided by eldarerathis works great, but I just want to mention that I had some trouble with the order of the subelements of the tag. I suggest you simply make another with the new subelements in that tag to avoid the problems I had. For instance my AndroidManifest.xml looks like this:

10 Answers 10

Please DO NOT use your own custom scheme like that. URI schemes are a network global namespace. Do you own the «anton:» scheme world-wide? No? Then DON’T use it.

One option is to have a web site, and have an intent-filter for a particular URI on that web site. For example, this is what Market does to intercept URIs on its web site:

Alternatively, there is the «intent:» scheme. This allows you to describe nearly any Intent as a URI, which the browser will try to launch when clicked. To build such a scheme, the best way is to just write the code to construct the Intent you want launched, and then print the result of intent.toUri(Intent.URI_INTENT_SCHEME).

You can use an action with this intent for to find any activity supporting that action. The browser will automatically add the BROWSABLE category to the intent before launching it, for security reasons; it also will strip any explicit component you have supplied for the same reason.

The best way to use this, if you want to ensure it launches only your app, is with your own scoped action and using Intent.setPackage() to say the Intent will only match your app package.

Trade-offs between the two:

http URIs require you have a domain you own. The user will always get the option to show the URI in the browser. It has very nice fall-back properties where if your app is not installed, they will simply land on your web site.

intent URIs require that your app already be installed and only on Android phones. The allow nearly any intent (but always have the BROWSABLE category included and not supporting explicit components). They allow you to direct the launch to only your app without the user having the option of instead going to the browser or any other app.

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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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