Android Intent

Android Intent : Android training in Chandigarh

Let us discuss about intents in android with android training in Chandigarh. An Android Intent is a question conveying an aim i.e. message 
starting with one part then onto the next segment inside the application or outside the application. The goals can convey messages among any 
of the three center segments of an application - exercises, administrations, and communicate beneficiaries. The goal itself, an Intent protest,
 is a uninvolved information structure holding a dynamic portrayal of a task to be performed.

For instance, we should expect, that you have an Activity that necessities to dispatch an email customer and sends an email utilizing your 
Android gadget. For this purpose,your Activity would send an ACTION_SEND alongside proper chooser, to the Android Intent Resolver. 
The predetermined chooser gives the best possible interface for the client to pick how to send your email information.

For instance, expect, that you have an Activity that requirements to open URL in a web program on your Android gadget. For this reason,
your Activity will send ACTION_WEB_SEARCH Intent to the Android Intent Resolver to open given URL in the web program. The Intent 
Resolver at that point passes your page to the web program and begins the Web Browser Activity. There are separate instruments for conveying
 goals to each kind of segment - exercises, administrations, and communicate recipients.

S.N. Method & Description

1 Context.startActivity() : The Intent question is passed to this technique to dispatch another movement or to get a current action to explore new territory.

2 Context.startService() : The Intent protest is passed to this strategy to start an administration or convey new guidelines to a continuous administration.

3 Context.sendBroadcast() : The Intent question is passed to this strategy to convey the message to all intrigued communicate recipients.

 INTENTS & FILTERS

Intent Objects

An Intent question is a heap of data which is utilized by the segment that gets the expectation in addition to data utilized by the Android framework.
An Intent question can contain the accompanying segments in light of what it is imparting or going to perform Action This is compulsory piece of 
the Intent protest and is a string naming the activity to be performed or, on account of communicate aims, the move that made place and is being 
accounted for. The activity generally decides how whatever remains of the aim question is organized.The Intent Resolver parses through a rundown 
of Activities and picks the one that would best match "The setData() technique indicates information just as a URI, setType() determines it just as a 
MIME write, and setDataAndType() indicates it as both a URI and a MIME compose."

Some examples of action/data pairs are: S.N. Action/Data Pair & Description

1. ACTION_VIEW content://contacts/people/1 Display information about the person whose identifier is "1".

2. ACTION_DIAL content://contacts/people/1 Display the phone dialer with the person filled in.

3. ACTION_VIEW tel:123 Display the phone dialer with the given number filled in.

4. ACTION_DIAL tel:123 Display the phone dialer with the given number filled in.

Android

5. ACTION_EDIT content://contacts/people/1

Edit information about the person whose identifier is "1".

6. ACTION_VIEW content://contacts/people/

Display a list of people, which the user can browse through.

Category

The classification is a discretionary piece of Intent protest and it's a string containing extra data about the sort of part that should deal with the goal. 
The addCategory() strategy puts a class in an Intent question, evacuate Category() erases a classification already included, and getCategories() gets
 the arrangement of all classifications at present in the protest. Here is a rundown of Android Intent

Standard Categories. You can check detail on Intent Filters in beneath segment to see how would we utilize classifications to pick fitting movement
 comparing to an Intent.

Extras

set and read using the putExtras() and getExtras() strategies independently. Here is an once-over of Android Intent Standard Extra Data.

Flags

It teach the android framework how to dispatch an action, these flags are discretionary piece of intent protest, and how to treat it after it is propelled 
and so forth.

Component Name

It is an android ComponentName protest speaking to either Activity, Services or BroadcastReceiver class. In the event that it is set, the Intent protest is 
conveyed to an occasion of the assigned class, generally Android utilizes other data in the Intent question find a reasonable target. The part name is 
set by setComponent(), setClass(), or setClassName() and read by getComponent().

Types of Intents

There are following two types of intents supported by Android till version 4.1

Android Explicit Intents

For example:

// Explicit Intent by specifying its class name

Intent i = new Intent(this, TargetActivity.class);

i.putExtra("Key1", "ABC");

i.putExtra("Key2", "123");

// Starts TargetActivity

startActivity(i);

Implicit Intents

These intents do not name a target and the field for the component name is left

blank. Implicit intents are often used to activate components in other

applications. For example:

// Implicit Intent by specifying a URI

Intent i = new Intent(Intent.ACTION_VIEW,

Uri.parse("http://www.example.com"));

// Starts Implicit Activity

startActivity(i);

The target component which receives the intent can use

the getExtras() method to get the extra data sent by the source component.

For example:

// Get bundle object at appropriate place in your code

Bundle extras = getIntent().getExtras();

// Extract data using passed keys

String value1 = extras.getString("Key1");

String value2 = extras.getString("Key2");

Example: Following is the example that shows the functionality of android intent applications which android build-in applications.

Step Description

1 You will use Eclipse IDE to create an Android application and name it as

IntentDemo under a package com.example.intentdemo. While creating

this project, make sure you Target SDK and Compile With at the latest

version of Android SDK to use higher levels of APIs.

2 Modify src/MainActivity.java file and add the code to define two listeners

corresponding two buttons i.e. Start Browser and Start Phone.

3 Modify layout XML file res/layout/activity_main.xml to add three buttons

in linear layout.

4 Modify res/values/strings.xml to define required constant values.

5 If you want to launch the android emulator applications, verify the result of changed done in application.

Following is the content of the modified main activity file

src/com.example.intentdemo/MainActivity.java.

package com.example.intent demo;

import android.net.Uri;

import android.os.Bundle;

import android.app.Activity;

import android.content.Intent;

import android.view.Menu;

import android.view.View;

import android.widget.Button;

public class MainActivity extends Activity {

@Override

protected void onCreate(Bundle savedInstanceState) {

Android super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

Button startBrowser = (Button) findViewById(R.id.start_browser);

startBrowser.setOnClickListener(new View.OnClickListener() {

public void onClick(View view) {

Intent i = new Intent(android.content.Intent.ACTION_VIEW,

Uri.parse("http://www.example.com"));

startActivity(i);

}

});

Button startPhone = (Button) findViewById(R.id.start_phone);

startPhone.setOnClickListener(new View.OnClickListener() {

public void onClick(View view) {

Intent i = new Intent(android.content.Intent.ACTION_VIEW,

Uri.parse("tel:9510300000"));

startActivity(i);

}

});

}

@Override

public boolean onCreateOptionsMenu(Menu menu) {

// Inflate the menu; this adds items to the action

// bar if it is present.

getMenuInflater().inflate(R.menu.main, menu);

return true;

}

}

Following will be the content of res/layout/activity_main.xml file:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

android:layout_width="fill_parent"

android:layout_height="fill_parent"



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