Using Intent in Android

Intent and intent filters in Android/Using intent to start a new activity/Intent Example in android

Ø  Intents are asynchronous messages which allow Android components to request functionality from other components of the Android system

Ø  Eg: an Activity can send an Intents to the Android system which starts another Activity

Ø  Intents are instances of the android.content.Intent class.

Ø  An Intent can also contain data. This data can be used by the receiving component

Ø  Eg: application can calls via an Intent a browser component. As data is it may send the URL to the browser component.

Ø  Intent  Flters  registers Activities, Services, Broadcast Receiver (as being capable of performing an action on a set  of data)

Ø  Two types of Intents:  Implicit Intents and Explicit Intent

Ø  Explicit Intents- component which should be called by the Android system, by using the Java class as identifier.

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

                   startActivity(i)

Ø  Implicit Intent: do not specify the Java class which should be called. They specify the action which should be performed and optionally an URI which should be used for this action

           Intent intent=new Intent(Intent.ACTION_VIEW,Uri.parse("http://www.brainbitz.in"));

          startActivity(intents)

You can use intents for a wide variety of tasks, but most often they’re used to start another activity.

In order to start Intent

Intent intent=new Intent(this,SecondActivity.class);

Constructor requires two parameters

Context

The Class of the app component to which the system should deliver the Intent 

An intent not only allows you to start another activity, but it can carry a bundle of data to the activity as well. An Intent can carry a collection of various data types as key-value pairs called extras. The putExtra() method takes the key name in the first parameter and the value in the second parameter.

Intent.putExtra(“reference_variable”,”data”); startActivity

Example
StartActivity.java

package com.example; import android.app.Activity; import android.content.Intent; import android.os.Bundle; import android.view.View; public class StartActivity extends Activity {       /** Called when the activity is first created. */       @Override       public void onCreate(Bundle savedInstanceState) {             super.onCreate(savedInstanceState);             setContentView(R.layout.main);       }       public void start(View v){             Intent intent=new Intent(this,SecondActivity.class);             startActivity(intent);       } }

SecondActivity.java

package com.example; import android.app.Activity; import android.os.Bundle; import android.widget.Toast; public class SecondActivity extends Activity{       @Override       protected void onCreate(Bundle savedInstanceState) {             // TODO Auto-generated method stub             super.onCreate(savedInstanceState);             String s=getIntent().getStringExtra("data");             Toast.makeText(this, s, Toast.LENGTH_LONG).show();       } }

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android"       package="com.example" android:versionCode="1" android:versionName="1.0">       <uses-sdk android:minSdkVersion="10" />       <application android:icon="@drawable/icon" android:label="@string/app_name">             <activity android:name=".StartActivity" android:label="@string/app_name">                   <intent-filter>                         <action android:name="android.intent.action.MAIN" />                         <category android:name="android.intent.category.LAUNCHER" />                   </intent-filter>             </activity>             <activity android:name=".SecondActivity"></activity>       </application> </manifest>