Tutorial

Intents can also be used to send broadcast messages into the Android system. BroadcastReceivers can register to event and will get notified if such an event is triggered.

Your application can register to system events, e.g. a new email has arrived, system boot is complete or a phone call is received and react accordingly.

As said earlier, since Android version 3.1 the Android system will per default exclude all BroadcastReceiver from receiving Intents if the corresponding application has never been started by the user or if the user explicitly stopped the application via the Android menu (in Manage Application).

Sometimes you want to find if an application has registered for a certain intent. For example you want to check if a certain receiver is available and if you enable some functionality in your app.

This can be done via checking the PackageManager. The following code checks if an intent exists. You can check via this method for intent and change your application behavior accordingly for example disable or hide menu items.

			
public boolean isIntentAvailable(Context context, String action) {
    final PackageManager packageManager = context.getPackageManager();
    final Intent intent = new Intent(action);
    List<ResolveInfo> resolveInfo =
            packageManager.queryIntentActivities(intent,
                    PackageManager.MATCH_DEFAULT_ONLY);
   if (resolveInfo.size() > 0) {
   		return true;
   	}
   return false;
}

		

The following assumes that you have already basic knowledge in Android development. Please check the Android development tutorial to learn the basics.

The following tutorial demonstrates how to use explicit Intents and how to transfer data between two Activities.

The first Activity will call the second one via an explicit intent. Once the user select the "Back" button on his phone the first Activity will receive some hard-coded data from the Sub-Activity.

Create a new Android application "de.vogella.android.intent.explicit" with the Activity called "ActivityOne".

Change the layout "main.xml" to the following.

			
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/TextView01"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:minHeight="60dip"
        android:text="First Activity. Press button to call second activity"
        android:textSize="20sp" >
    </TextView>

    <Button
        android:id="@+id/Button01"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="onClick"
        android:text="Calling an intent" >
    </Button>

</LinearLayout>
		

Create the layout "second.xml".

			
<?xml version="1.0" encoding="utf-8"?>
<GridLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:alignmentMode="alignBounds"
    android:columnCount="2"
    android:columnOrderPreserved="false"
    android:useDefaultMargins="true" >

    <TextView
        android:layout_gravity="center_horizontal"
        android:text="Input 1"
        android:textSize="32dip" />

    <EditText
        android:id="@+id/input1"
        android:layout_gravity="fill_horizontal"
        android:text="Default" />

    <TextView
        android:layout_gravity="center_horizontal"
        android:text="Input 2"
        android:textSize="32dip" />

    <EditText
        android:id="@+id/input2"
        android:layout_gravity="fill_horizontal"
        android:text="Default" />

 
    <Button
        android:layout_column="1"
        android:layout_gravity="right"
        android:width="80dp"
        android:onClick="onClick"
        android:text="Finish" />

</GridLayout>
		

Declare a new Activity called "ActivityTwo" via the "AndroidManifest.xml" file.

			
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="de.vogella.android.intent.explicit"
      android:versionCode="1"
      android:versionName="1.0">
    <application android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name=".ActivityOne"
                  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:label="ActivityTwo" android:name="ActivityTwo"></activity>
</application>
    <uses-sdk android:minSdkVersion="9" />

</manifest> 
		

Create the following coding for your two Activities.

			
package de.vogella.android.intent.explicit;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Toast;

public class ActivityOne extends Activity {
	private static final int REQUEST_CODE = 10;

	
/** Called when the activity is first created. */
	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
	}

	public void onClick(View view) {
		Intent i = new Intent(this, ActivityTwo.class);
		i.putExtra("Value1", "This value one for ActivityTwo ");
		i.putExtra("Value2", "This value two ActivityTwo");
		// Set the request code to any code you like, you can identify the
		// callback via this code
		startActivityForResult(i, REQUEST_CODE);
	}

	@Override
	protected void onActivityResult(int requestCode, int resultCode, Intent data) {
		if (resultCode == RESULT_OK && requestCode == REQUEST_CODE) {
			if (data.hasExtra("returnKey1")) {
				Toast.makeText(this, data.getExtras().getString("returnKey1"),
						Toast.LENGTH_SHORT).show();
			}
		}
	}
}
		

			
package de.vogella.android.intent.explicit;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;

public class ActivityTwo extends Activity {

	
/** Called when the activity is first created. */
	@Override
	public void onCreate(Bundle bundle) {
		super.onCreate(bundle);
		setContentView(R.layout.second);
		Bundle extras = getIntent().getExtras();
		if (extras == null) {
			return;
		}
		String value1 = extras.getString("Value1");
		String value2 = extras.getString("Value2");
		if (value1 != null && value2 != null) {
			EditText text1 = (EditText) findViewById(R.id.input1);
			EditText text2 = (EditText) findViewById(R.id.input2);
			text1.setText(value1);
			text2.setText(value2);
		}
	}

	public void onClick(View view) {
		finish();
	}

	@Override
	public void finish() {
		Intent data = new Intent();
		// Return some hard-coded values
		data.putExtra("returnKey1", "Swinging on a star. ");
		data.putExtra("returnKey2", "You could be better then you are. ");
		setResult(RESULT_OK, data);
		super.finish();
	}
}

		

Run your application. The first will send data to the second Activity which will be shown on the user interface. If you select back on your phone, the first Activity will display a Toast with the data from the second Activity.

The following tutorial demonstrates the usage of implicit intents of the Android System.

Create a new Android application "de.vogella.android.intent.implicit" with a Activity called " CallIntentsActivity ".

In this example we will use a Spinner to select the Intent which should get triggered. For the content of the Spinner we will define static values.

Create the following "intents.xml" file in the "res/values" folder.

			
<resources>
    <string-array name="intents">
        <item>Open Browser</item>
        <item>Call Someone</item>
        <item>Dial</item>
        <item>Show Map</item>
        <item>Search on Map</item>
        <item>Take picture</item>
        <item>Show contacts</item>
        <item>Edit first contact</item>
    </string-array>
    
</resources>
		

Change the layout file "main.xml" to the following.

			
<?xml version="1.0" encoding="utf-8"?>
<GridLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:alignmentMode="alignBounds"
    android:columnCount="1" >

      <Spinner
        android:id="@+id/spinner"
        android:layout_gravity="fill_horizontal"
        android:drawSelectorOnTop="true"
        >
      </Spinner>
    
    <Button
        android:id="@+id/trigger"
        android:onClick="onClick"
        android:text="Trigger Intent">
    </Button>

  
</GridLayout>
		

To be able to use certain intents you need to register then for your application. Maintain the following "AndroidManifest.xml".

			
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="de.vogella.android.intent.implicit"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk android:minSdkVersion="15" />

    <uses-permission android:name="android.permission.CALL_PRIVILEGED" >
    </uses-permission>
    <uses-permission android:name="android.permission.CALL_PHONE" >
    </uses-permission>
    <uses-permission android:name="android.permission.CAMERA" >
    </uses-permission>
    <uses-permission android:name="android.permission.READ_CONTACTS" >
    </uses-permission>
    <uses-permission android:name="android.permission.INTERNET"/>

    <application
        android:icon="@drawable/icon"
        android:label="@string/app_name" >
        <activity
            android:name=".CallIntentsActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>
		

Change your activity to the following. We will start the new intent with the method startActivityForResult() which allow us to specify a desired result code. Once the intent is finished the method onActivityResult() is called and you can perform actions based on the result of the activity.

			
package de.vogella.android.intent.implicit;

import android.app.Activity;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Spinner;
import android.widget.Toast;

public class CallIntentsActivity extends Activity {
	private Spinner spinner;

	
/** Called when the activity is first created. */
	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		spinner = (Spinner) findViewById(R.id.spinner);
		ArrayAdapter adapter = ArrayAdapter.createFromResource(this,
				R.array.intents, android.R.layout.simple_spinner_item);
		adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
		spinner.setAdapter(adapter);
	}

	public void onClick(View view) {
		int position = spinner.getSelectedItemPosition();
		Intent intent = null;
		switch (position) {
		case 0:
			intent = new Intent(Intent.ACTION_VIEW,
					Uri.parse("http://www.vogella.de"));
			break;
		case 1:
			intent = new Intent(Intent.ACTION_CALL,
					Uri.parse("tel:(+49)12345789"));
			break;
		case 2:
			break;
		case 3:
			intent = new Intent(Intent.ACTION_DIAL,
					Uri.parse("tel:(+49)12345789"));
			startActivity(intent);
			break;
		case 4:
			intent = new Intent(Intent.ACTION_VIEW,
					Uri.parse("geo:50.123,7.1434?z=19"));
			break;
		case 5:
			intent = new Intent(Intent.ACTION_VIEW,
					Uri.parse("geo:0,0?q=query"));
			break;
		case 6:
			intent = new Intent("android.media.action.IMAGE_CAPTURE");
			break;
		case 7:
			intent = new Intent(Intent.ACTION_VIEW,
					Uri.parse("content://contacts/people/"));
			break;
		case 8:
			intent = new Intent(Intent.ACTION_EDIT,
					Uri.parse("content://contacts/people/1"));
			break;

		}
		if (intent != null) {
			startActivity(intent);
		}
	}

	@Override
	public void onActivityResult(int requestCode, int resultCode, Intent data) {
		if (resultCode == Activity.RESULT_OK && requestCode == 0) {
			String result = data.toURI();
			Toast.makeText(this, result, Toast.LENGTH_LONG);
		}
	}
}
		

If you start your application you should see an list of buttons and if you press the button, different activities should be performed. Note that you didn't specify any receiving application only the thing that should be done.

The following example will register a Activity for the Intent which is triggered to view a http webpage.

Our application downloads the HTML source of this page and display this in a TextView.

Create the Android project "de.vogella.android.intent. " with the activity "BrowserActivitiy". Register your Activity to the Intent via the Intent.Action_VIEW action and the scheme "http" via the following "AndroidManifest.xml". The manifest also declares the permission to access the Internet.

			
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="de.vogella.android.intent.browserfilter"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk android:minSdkVersion="15" />

    <uses-permission android:name="android.permission.INTERNET" >
    </uses-permission>

    <application
        android:icon="@drawable/icon"
        android:label="@string/app_name" >
        <activity
            android:name=".BrowserActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.VIEW" />

                <category android:name="android.intent.category.DEFAULT" />

                <data android:scheme="http" />
            </intent-filter>
        </activity>
    </application>

</manifest>
		

Change "main.xml" to the following.

			
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
<TextView  
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:id="@+id/textView"/>
</LinearLayout>

		

Install your application. If you now trigger an Intent to open an URL your should be able to select your own component. You can for example trigger this Intent via the example from the implicit tutorials.

			
package de.vogella.android.intent.browserfilter;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.URL;

import android.app.Activity;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.os.StrictMode;
import android.widget.TextView;

public class BrowserActivity extends Activity {
	
/** Called when the activity is first created. */
	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);

		// To keep this example simple, we allow network access
		// in the user interface thread
		StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder()
				.permitAll().build();
		StrictMode.setThreadPolicy(policy);

		setContentView(R.layout.main);
		Intent intent = getIntent();
		TextView text = (TextView) findViewById(R.id.textView);
		// To get the action of the intent use
		String action = intent.getAction();
		if (action != Intent.ACTION_VIEW) {
			throw new RuntimeException("Should not happen");
		}
		// To get the data use
		Uri data = intent.getData();
		URL url;
		try {
			url = new URL(data.getScheme(), data.getHost(), data.getPath());
			BufferedReader rd = new BufferedReader(new InputStreamReader(
					url.openStream()));
			String line = "";
			while ((line = rd.readLine()) != null) {
				text.append(line);
			}

		} catch (Exception e) {
			e.printStackTrace();
		}

	}
}
		

If you select you component the HTML code should be loaded into your text view.

Please help me to support this article:

Before posting questions, please see the vogella FAQ. If you have questions or find an error in this article please use the www.vogella.de Google Group. I have created a short list how to create good questions which might also help you.