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How to redirect from own application another application?

I am creating my own app and at one point I want that user can go to any other application.So what will be the best code for that?

You can do that in many ways, but one of the common method is intents. You can create implicit intents for this purpose.
here is a sample code :
//From MainActivity.onCreate()
Intent intent = new Intent(Intent.ACTION_VIEW,Uri.parse("http://google.com"));
startActivity(intent);`
you can find further details about intents here.

Which function does intent have? [duplicate]

This question already has answers here:
What is an Intent in Android?
(14 answers)
Closed 8 years ago.
I dont know much about intent (or android) so.. Can someone please explain me what is it exactly? i have search on the internet, A LOT.
Also what does each line of this code do?
Intent intent = new Intent (this, DisplayMessageActivity.class);
intent.putExtra("a", "b");
Thanks in advance

I suggest reading Android Intents
You couldn't have search for very long, since this is very basic topic.
I suggest you read more of Android's API guides.
Line 1 = Create message that describes what to do, in this case start "DisplayMessagActivity"
Line 2 = Add content to the message

Intent intent = new Intent (this, DisplayMessageActivity.class);
For this line, its function is to create a navigation from the current activity/page to the displaymessageactivity page.
it is like from here to there.
For this intent.putExtra("a", "b"); the purpose of this is to put like a temp storage/variable to pass to the next page for retrieval. In this case, you put the value "b" in the variable "a". With this method, you can use the value on the other activity or page.
All the above are just storing of info, it is not executed yet. if you want to execute the intent do the following
startActivity(intent);

The best example to state the behavior of Intent is it behaves like a POSTMAN that delivers message to the stated address.
Whether it may be calling service ,BroadCastRecivers ,Activity they are used in number of occassion.
Intents are asynchronous messages which allow application components
to request functionality from other Android components. Intents allow
you to interact with components from the same applications as well as
with components contributed by other applications. For example, an
activity can start an external activity for taking a picture.
Intents are objects of the android.content.Intent type. Your code can
send them to the Android system defining the components you are
targeting. For example, via the startActivity() method you can define
that the intent should be used to start an activity.
An intent can contain data via a Bundle. This data can be used by the
receiving component.
Intents can be used to start Service, call Activty, call Sub Activity, transfer the data between Activity or retrieve the data from Activity

Can I send Intent to another app

I m creating an app which opens another app in the background and my first app will be sending some string as a data to another app, so can I send Intents to another app's like we usually send intents to other classes containing data?
If we can then how can I send it?

Yes , you can send the intent to any app you like but its upto the receiving application to handle it.
Few apps may crash receiving it.
The way
Make an intent
Intent i=new Intent(yourContext,Activity_to_which_you_to_send.class);
Put some data-if you want to
i.putExtraString("key","value");
or put using a bundle
Bundle b=new Bundle();
b.putString(key,boolean_value);
b.putBoolean(key,boolean_value)
Starting the activity
startActivity(i);
Set the package of the app
i.setPackage("com.whatsapp");
Example
if you want to find out the main Activity of an app
go to command line
type adb shell pm -lf
pick any one and try it by passing as a second argument to the intent constructor defined above and then call startActivity method.
hope it helps you.

Intent intent = new Intent(Intent.ACTION_VIEW);
intent.setType("text/plain");
intent.putExtra(name,yourString);
try{
startActivity(intent);
} catch (Exception ActivityNotFoundException){
ActivityNotFoundException.printStackTrace();
}
Use this code to send an intent to another app and specify the name value and string in putExtra function.

Yes you can send Intent to another app like we send to other classes with passing data as a string so you can see it HERE

Yes. "App" is not so well defined on Android, it's a loose term. Intents are used to start an Activity, among other things.

Android: getting info on the calling app from activity

I want to implement a fine-granularity protection mechanism in an exported activity. The permissions framework does not seem to work for my requirements.
There are two options I am considering:
using Activity.getCallingPackage - only works if the activity is started with startActivityForResult - this is a limitation I would like to avoid if possible.
using Binder.getCallingUid - when called in an Activity, it returns the local UID, and not the calling UID.
Is there any way to allow activities started with startActivity to retrieve any information about the calling app?

You can add extra information in your intent.
Intent i = new Intent(this, NextClass.class);
i.putExtra("extra", "This is some extra information";
startActivity(i);
You retrieve the data from NextClass by:
Intent i = getIntent();
String extraStuff = i.getStringExtra("extra");

Is there any way to allow activities started with startActivity to retrieve any information about the calling app?
No, sorry, beyond your startActivityForResult() hack. Android's support for "a fine-granularity protection mechanism" is designed around services, not activities or other components.

difference between intent and intenfilter in android

Hi friends
can anybody tell what is the use of intent filter and what is difference between intent and intent filter
Thanks

An Intent is an object passed to Context.startActivity(),Context.startService() or Activity.startActivityForResult() etc. to launch an activity or get an existing activity to do something new.
While an Intent filter describes a capability of the component(like activities, services, and broadcast receivers )
For more details see this

Intent's are used to start new activity from the current activity. With two ways
1) Activity.startActivity(intent);
2) Activity.startActivityForResult(intent,rqwuestCode);
//The above thing's you need to put in .java file
Intent-filter you need to mention on manifeast file.
// Intent filter are used for broadcast receiver. Whenever the intent filter condition is match the android OS will launch that activity.

An intent is an object that can hold the os or other app activity and its data in uri form.It is started using startActivity(intent-obj)..\n whereas IntentFilter can fetch activity information on os or other app activities.