docs/html/training/basics/intents/sending.jd - platform/frameworks/base - Git at Google

 page.title=Sending the User to Another App
 parent.title=Interacting with Other Apps
 parent.link=index.html

 trainingnavtop=true
 next.title=Getting a Result from an Activity
 next.link=result.html

 @jd:body


 <div id="tb-wrapper">
   <div id="tb">

 <h2>This lesson teaches you to</h2>
 <ol>
   <li><a href="#Build">Build an Implicit Intent</a></li>
   <li><a href="#Verify">Verify There is an App to Receive the Intent</a></li>
   <li><a href="#StartActivity">Start an Activity with the Intent</a></li>
   <li><a href="#AppChooser">Show an App Chooser</a></li>
 </ol>

 <h2>You should also read</h2>
 <ul>
   <li><a href="{@docRoot}training/sharing/index.html">Sharing Content</a></li>
 </ul>

   </div>
 </div>

 <p>One of Android's most important features is an app's ability to send the user to another app
 based on an "action" it would like to perform. For example, if
 your app has the address of a business that you'd like to show on a map, you don't have to build
 an activity in your app that shows a map. Instead, you can create a request to view the address
 using an {@link android.content.Intent}. The Android system then starts an app that's able to show
 the address on a map.</p>

 <p>As explained in the first class, <a href="{@docRoot}training/basics/firstapp/index.html">Building
 Your First App</a>, you must use intents to navigate between activities in your own app. You
 generally do so with an <em>explicit intent</em>, which defines the exact class name of the
 component you want to start. However, when you want to have a separate app perform an action, such
 as "view a map," you must use an <em>implicit intent</em>.</p>

 <p>This lesson shows you how to create an implicit intent for a particular action, and how to use it
 to start an activity that performs the action in another app.</p>


 <h2 id="Build">Build an Implicit Intent</h2>

 <p>Implicit intents do not declare the class name of the component to start, but instead declare an
 action to perform. The action specifies the thing you want to do, such as <em>view</em>,
 <em>edit</em>, <em>send</em>, or <em>get</em> something. Intents often also include data associated
 with the action, such as the address you want to view, or the email message you want to send.
 Depending on the intent you want to create, the data might be a {@link android.net.Uri},
 one of several other data types, or the intent might not need data at all.</p>

 <p>If your data is a {@link android.net.Uri}, there's a simple {@link
 android.content.Intent#Intent(String,Uri) Intent()} constructor you can use define the action and
 data.</p>

 <p>For example, here's how to create an intent to initiate a phone call using the {@link
 android.net.Uri} data to specify the telephone number:</p>

 <pre>
 Uri number = Uri.parse("tel:5551234");
 Intent callIntent = new Intent(Intent.ACTION_DIAL, number);
 </pre>

 <p>When your app invokes this intent by calling {@link android.app.Activity#startActivity
 startActivity()}, the Phone app initiates a call to the given phone number.</p>

 <p>Here are a couple other intents and their action and {@link android.net.Uri} data
 pairs:</p>

 <ul>
   <li>View a map:
 <pre>
 // Map point based on address
 Uri location = Uri.parse("geo:0,0?q=1600+Amphitheatre+Parkway,+Mountain+View,+California");
 // Or map point based on latitude/longitude
 // Uri location = Uri.parse("geo:37.422219,-122.08364?z=14"); // z param is zoom level
 Intent mapIntent = new Intent(Intent.ACTION_VIEW, location);
 </pre>
   </li>
   <li>View a web page:
 <pre>
 Uri webpage = Uri.parse("http://www.android.com");
 Intent webIntent = new Intent(Intent.ACTION_VIEW, webpage);
 </pre>
   </li>
 </ul>

 <p>Other kinds of implicit intents require "extra" data that provide different data types,
 such as a string. You can add one or more pieces of extra data using the various {@link
 android.content.Intent#putExtra(String,String) putExtra()} methods.</p>

 <p>By default, the system determines the appropriate MIME type required by an intent based on the
 {@link android.net.Uri} data that's included. If you don't include a {@link android.net.Uri} in the
 intent, you should usually use {@link android.content.Intent#setType setType()} to specify the type
 of data associated with the intent. Setting the MIME type further specifies which kinds of
 activities should receive the intent.</p>

 <p>Here are some more intents that add extra data to specify the desired action:</p>

 <ul>
   <li>Send an email with an attachment:
 <pre>
 Intent emailIntent = new Intent(Intent.ACTION_SEND);
 // The intent does not have a URI, so declare the "text/plain" MIME type
 emailIntent.setType(HTTP.PLAIN_TEXT_TYPE);
 emailIntent.putExtra(Intent.EXTRA_EMAIL, new String[] {"jon@example.com"}); // recipients
 emailIntent.putExtra(Intent.EXTRA_SUBJECT, "Email subject");
 emailIntent.putExtra(Intent.EXTRA_TEXT, "Email message text");
 emailIntent.putExtra(Intent.EXTRA_STREAM, Uri.parse("content://path/to/email/attachment"));
 // You can also attach multiple items by passing an ArrayList of Uris
 </pre>
   </li>
   <li>Create a calendar event:
 <pre>
 Intent calendarIntent = new Intent(Intent.ACTION_INSERT, Events.CONTENT_URI);
 Calendar beginTime = Calendar.getInstance().set(2012, 0, 19, 7, 30);
 Calendar endTime = Calendar.getInstance().set(2012, 0, 19, 10, 30);
 calendarIntent.putExtra(CalendarContract.EXTRA_EVENT_BEGIN_TIME, beginTime.getTimeInMillis());
 calendarIntent.putExtra(CalendarContract.EXTRA_EVENT_END_TIME, endTime.getTimeInMillis());
 calendarIntent.putExtra(Events.TITLE, "Ninja class");
 calendarIntent.putExtra(Events.EVENT_LOCATION, "Secret dojo");
 </pre>
 <p class="note"><strong>Note:</strong> This intent for a calendar event is supported only with API
 level 14 and higher.</p>
   </li>
 </ul>

 <p class="note"><strong>Note:</strong> It's important that you define your {@link
 android.content.Intent} to be as specific as possible. For example, if you want to display an image
 using the {@link android.content.Intent#ACTION_VIEW} intent, you should specify a MIME type of
 {@code image/*}. This prevents apps that can "view" other types of data (like a map app) from being
 triggered by the intent.</p>


 <h2 id="Verify">Verify There is an App to Receive the Intent</h2>

 <p>Although the Android platform guarantees that certain intents will resolve to one of the
 built-in apps (such as the Phone, Email, or Calendar app), you should always include a
 verification step before invoking an intent.</p>

 <p class="caution"><strong>Caution:</strong> If you invoke an intent and there is no app
 available on the device that can handle the intent, your app will crash.</p>

 <p>To verify there is an activity available that can respond to the intent, call {@link
 android.content.pm.PackageManager#queryIntentActivities queryIntentActivities()} to get a list
 of activities capable of handling your {@link android.content.Intent}. If the returned {@link
 java.util.List} is not empty, you can safely use the intent. For example:</p>

 <pre>
 PackageManager packageManager = {@link android.content.Context#getPackageManager()};
 List&lt;ResolveInfo> activities = packageManager.queryIntentActivities(intent, 0);
 boolean isIntentSafe = activities.size() > 0;
 </pre>

 <p>If <code>isIntentSafe</code> is <code>true</code>, then at least one app will respond to
 the intent. If it is <code>false</code>, then there aren't any apps to handle the intent.</p>

 <p class="note"><strong>Note:</strong> You should perform this check when your activity first
 starts in case you need to disable the feature that uses the intent before the user attempts to use
 it. If you know of a specific app that can handle the intent, you can also provide a link for the
 user to download the app (see how to <a
 href="{@docRoot}distribute/googleplay/promote/linking.html">link to your product on Google
 Play</a>).</p>


 <h2 id="StartActivity">Start an Activity with the Intent</h2>

 <div class="figure" style="width:200px">
   <img src="{@docRoot}images/training/basics/intents-choice.png" alt="" />
   <p class="img-caption"><strong>Figure 1.</strong> Example of the selection dialog that appears
 when more than one app can handle an intent.</p>
 </div>

 <p>Once you have created your {@link android.content.Intent} and set the extra info, call {@link
 android.app.Activity#startActivity startActivity()} to send it to the system. If the system
 identifies more than one activity that can handle the intent, it displays a dialog for the user to
 select which app to use, as shown in figure 1. If there is only one activity that handles the
 intent, the system immediately starts it.</p>

 <pre>
 startActivity(intent);
 </pre>

 <p>Here's a complete example that shows how to create an intent to view a map, verify that an
 app exists to handle the intent, then start it:</p>

 <pre>
 // Build the intent
 Uri location = Uri.parse("geo:0,0?q=1600+Amphitheatre+Parkway,+Mountain+View,+California");
 Intent mapIntent = new Intent(Intent.ACTION_VIEW, location);

 // Verify it resolves
 PackageManager packageManager = {@link android.content.Context#getPackageManager()};
 List&lt;ResolveInfo> activities = packageManager.queryIntentActivities(mapIntent, 0);
 boolean isIntentSafe = activities.size() > 0;

 // Start an activity if it's safe
 if (isIntentSafe) {
     startActivity(mapIntent);
 }
 </pre>


 <h2 id="AppChooser">Show an App Chooser</h2>

 <div class="figure" style="width:200px">
   <img src="{@docRoot}images/training/basics/intent-chooser.png" alt="" />
   <p class="img-caption"><strong>Figure 2.</strong> Example of the chooser dialog that appears
 when you use {@link android.content.Intent#createChooser createChooser()} to ensure
 that the user is always shown a list of apps that respond to your intent.</p>
 </div>

 <p>Notice that when you start an activity by passing your {@link android.content.Intent} to {@link
 android.app.Activity#startActivity startActivity()} and there is more than one app that responds to
 the intent, the user can select which app to use by default (by selecting a checkbox at the bottom
 of the dialog; see figure 1). This is nice when performing an action for which the user
 generally wants to use the same app every time, such as when opening a web page (users
 likely use just one web browser) or taking a photo (users likely prefer one camera). However, if
 the action to be performed could be handled by multiple apps and the user might
 prefer a different app each time&mdash;such as a "share" action, for which users might have several
 apps through which they might share an item&mdash;you should explicitly show a chooser dialog,
 which forces the user to select which app to use for the action every time (the user cannot select a
 default app for the action).</p>

 <p>To show the chooser, create an {@link android.content.Intent} using {@link
 android.content.Intent#createChooser createChooser()} and pass it to {@link
 android.app.Activity#startActivity startActivity()}. For example:</p>

 <pre>
 Intent intent = new Intent(Intent.ACTION_SEND);
 ...

 // Always use string resources for UI text. This says something like "Share this photo with"
 String title = getResources().getText(R.string.chooser_title);
 // Create and start the chooser
 Intent chooser = Intent.createChooser(intent, title);
 startActivity(chooser);
 </pre>

 <p>This displays a dialog with a list of apps that respond to the intent passed to the {@link
 android.content.Intent#createChooser createChooser()} method and uses the supplied text as the
 dialog title.</p>
	page.title=Sending the User to Another App
	parent.title=Interacting with Other Apps
	parent.link=index.html

	trainingnavtop=true
	next.title=Getting a Result from an Activity
	next.link=result.html

	@jd:body


	<div id="tb-wrapper">
	<div id="tb">

	<h2>This lesson teaches you to</h2>
	<ol>
	<li><a href="#Build">Build an Implicit Intent</a></li>
	<li><a href="#Verify">Verify There is an App to Receive the Intent</a></li>
	<li><a href="#StartActivity">Start an Activity with the Intent</a></li>
	<li><a href="#AppChooser">Show an App Chooser</a></li>
	</ol>

	<h2>You should also read</h2>
	<ul>
	<li><a href="{@docRoot}training/sharing/index.html">Sharing Content</a></li>
	</ul>

	</div>
	</div>

	<p>One of Android's most important features is an app's ability to send the user to another app
	based on an "action" it would like to perform. For example, if
	your app has the address of a business that you'd like to show on a map, you don't have to build
	an activity in your app that shows a map. Instead, you can create a request to view the address
	using an {@link android.content.Intent}. The Android system then starts an app that's able to show
	the address on a map.</p>

	<p>As explained in the first class, <a href="{@docRoot}training/basics/firstapp/index.html">Building
	Your First App</a>, you must use intents to navigate between activities in your own app. You
	generally do so with an <em>explicit intent</em>, which defines the exact class name of the
	component you want to start. However, when you want to have a separate app perform an action, such
	as "view a map," you must use an <em>implicit intent</em>.</p>

	<p>This lesson shows you how to create an implicit intent for a particular action, and how to use it
	to start an activity that performs the action in another app.</p>



	<h2 id="Build">Build an Implicit Intent</h2>

	<p>Implicit intents do not declare the class name of the component to start, but instead declare an
	action to perform. The action specifies the thing you want to do, such as <em>view</em>,
	<em>edit</em>, <em>send</em>, or <em>get</em> something. Intents often also include data associated
	with the action, such as the address you want to view, or the email message you want to send.
	Depending on the intent you want to create, the data might be a {@link android.net.Uri},
	one of several other data types, or the intent might not need data at all.</p>

	<p>If your data is a {@link android.net.Uri}, there's a simple {@link
	android.content.Intent#Intent(String,Uri) Intent()} constructor you can use define the action and
	data.</p>

	<p>For example, here's how to create an intent to initiate a phone call using the {@link
	android.net.Uri} data to specify the telephone number:</p>

	<pre>
	Uri number = Uri.parse("tel:5551234");
	Intent callIntent = new Intent(Intent.ACTION_DIAL, number);
	</pre>

	<p>When your app invokes this intent by calling {@link android.app.Activity#startActivity
	startActivity()}, the Phone app initiates a call to the given phone number.</p>

	<p>Here are a couple other intents and their action and {@link android.net.Uri} data
	pairs:</p>

	<ul>
	<li>View a map:
	<pre>
	// Map point based on address
	Uri location = Uri.parse("geo:0,0?q=1600+Amphitheatre+Parkway,+Mountain+View,+California");
	// Or map point based on latitude/longitude
	// Uri location = Uri.parse("geo:37.422219,-122.08364?z=14"); // z param is zoom level
	Intent mapIntent = new Intent(Intent.ACTION_VIEW, location);
	</pre>
	</li>
	<li>View a web page:
	<pre>
	Uri webpage = Uri.parse("http://www.android.com");
	Intent webIntent = new Intent(Intent.ACTION_VIEW, webpage);
	</pre>
	</li>
	</ul>

	<p>Other kinds of implicit intents require "extra" data that provide different data types,
	such as a string. You can add one or more pieces of extra data using the various {@link
	android.content.Intent#putExtra(String,String) putExtra()} methods.</p>

	<p>By default, the system determines the appropriate MIME type required by an intent based on the
	{@link android.net.Uri} data that's included. If you don't include a {@link android.net.Uri} in the
	intent, you should usually use {@link android.content.Intent#setType setType()} to specify the type
	of data associated with the intent. Setting the MIME type further specifies which kinds of
	activities should receive the intent.</p>

	<p>Here are some more intents that add extra data to specify the desired action:</p>

	<ul>
	<li>Send an email with an attachment:
	<pre>
	Intent emailIntent = new Intent(Intent.ACTION_SEND);
	// The intent does not have a URI, so declare the "text/plain" MIME type
	emailIntent.setType(HTTP.PLAIN_TEXT_TYPE);
	emailIntent.putExtra(Intent.EXTRA_EMAIL, new String[] {"jon@example.com"}); // recipients
	emailIntent.putExtra(Intent.EXTRA_SUBJECT, "Email subject");
	emailIntent.putExtra(Intent.EXTRA_TEXT, "Email message text");
	emailIntent.putExtra(Intent.EXTRA_STREAM, Uri.parse("content://path/to/email/attachment"));
	// You can also attach multiple items by passing an ArrayList of Uris
	</pre>
	</li>
	<li>Create a calendar event:
	<pre>
	Intent calendarIntent = new Intent(Intent.ACTION_INSERT, Events.CONTENT_URI);
	Calendar beginTime = Calendar.getInstance().set(2012, 0, 19, 7, 30);
	Calendar endTime = Calendar.getInstance().set(2012, 0, 19, 10, 30);
	calendarIntent.putExtra(CalendarContract.EXTRA_EVENT_BEGIN_TIME, beginTime.getTimeInMillis());
	calendarIntent.putExtra(CalendarContract.EXTRA_EVENT_END_TIME, endTime.getTimeInMillis());
	calendarIntent.putExtra(Events.TITLE, "Ninja class");
	calendarIntent.putExtra(Events.EVENT_LOCATION, "Secret dojo");
	</pre>
	<p class="note"><strong>Note:</strong> This intent for a calendar event is supported only with API
	level 14 and higher.</p>
	</li>
	</ul>

	<p class="note"><strong>Note:</strong> It's important that you define your {@link
	android.content.Intent} to be as specific as possible. For example, if you want to display an image
	using the {@link android.content.Intent#ACTION_VIEW} intent, you should specify a MIME type of
	{@code image/*}. This prevents apps that can "view" other types of data (like a map app) from being
	triggered by the intent.</p>



	<h2 id="Verify">Verify There is an App to Receive the Intent</h2>

	<p>Although the Android platform guarantees that certain intents will resolve to one of the
	built-in apps (such as the Phone, Email, or Calendar app), you should always include a
	verification step before invoking an intent.</p>

	<p class="caution"><strong>Caution:</strong> If you invoke an intent and there is no app
	available on the device that can handle the intent, your app will crash.</p>

	<p>To verify there is an activity available that can respond to the intent, call {@link
	android.content.pm.PackageManager#queryIntentActivities queryIntentActivities()} to get a list
	of activities capable of handling your {@link android.content.Intent}. If the returned {@link
	java.util.List} is not empty, you can safely use the intent. For example:</p>

	<pre>
	PackageManager packageManager = {@link android.content.Context#getPackageManager()};
	List<ResolveInfo> activities = packageManager.queryIntentActivities(intent, 0);
	boolean isIntentSafe = activities.size() > 0;
	</pre>

	<p>If <code>isIntentSafe</code> is <code>true</code>, then at least one app will respond to
	the intent. If it is <code>false</code>, then there aren't any apps to handle the intent.</p>

	<p class="note"><strong>Note:</strong> You should perform this check when your activity first
	starts in case you need to disable the feature that uses the intent before the user attempts to use
	it. If you know of a specific app that can handle the intent, you can also provide a link for the
	user to download the app (see how to <a
	href="{@docRoot}distribute/googleplay/promote/linking.html">link to your product on Google
	Play</a>).</p>


	<h2 id="StartActivity">Start an Activity with the Intent</h2>

	<div class="figure" style="width:200px">
	<img src="{@docRoot}images/training/basics/intents-choice.png" alt="" />
	<p class="img-caption"><strong>Figure 1.</strong> Example of the selection dialog that appears
	when more than one app can handle an intent.</p>
	</div>

	<p>Once you have created your {@link android.content.Intent} and set the extra info, call {@link
	android.app.Activity#startActivity startActivity()} to send it to the system. If the system
	identifies more than one activity that can handle the intent, it displays a dialog for the user to
	select which app to use, as shown in figure 1. If there is only one activity that handles the
	intent, the system immediately starts it.</p>

	<pre>
	startActivity(intent);
	</pre>

	<p>Here's a complete example that shows how to create an intent to view a map, verify that an
	app exists to handle the intent, then start it:</p>

	<pre>
	// Build the intent
	Uri location = Uri.parse("geo:0,0?q=1600+Amphitheatre+Parkway,+Mountain+View,+California");
	Intent mapIntent = new Intent(Intent.ACTION_VIEW, location);

	// Verify it resolves
	PackageManager packageManager = {@link android.content.Context#getPackageManager()};
	List<ResolveInfo> activities = packageManager.queryIntentActivities(mapIntent, 0);
	boolean isIntentSafe = activities.size() > 0;

	// Start an activity if it's safe
	if (isIntentSafe) {
	startActivity(mapIntent);
	}
	</pre>



	<h2 id="AppChooser">Show an App Chooser</h2>

	<div class="figure" style="width:200px">
	<img src="{@docRoot}images/training/basics/intent-chooser.png" alt="" />
	<p class="img-caption"><strong>Figure 2.</strong> Example of the chooser dialog that appears
	when you use {@link android.content.Intent#createChooser createChooser()} to ensure
	that the user is always shown a list of apps that respond to your intent.</p>
	</div>

	<p>Notice that when you start an activity by passing your {@link android.content.Intent} to {@link
	android.app.Activity#startActivity startActivity()} and there is more than one app that responds to
	the intent, the user can select which app to use by default (by selecting a checkbox at the bottom
	of the dialog; see figure 1). This is nice when performing an action for which the user
	generally wants to use the same app every time, such as when opening a web page (users
	likely use just one web browser) or taking a photo (users likely prefer one camera). However, if
	the action to be performed could be handled by multiple apps and the user might
	prefer a different app each time—such as a "share" action, for which users might have several
	apps through which they might share an item—you should explicitly show a chooser dialog,
	which forces the user to select which app to use for the action every time (the user cannot select a
	default app for the action).</p>

	<p>To show the chooser, create an {@link android.content.Intent} using {@link
	android.content.Intent#createChooser createChooser()} and pass it to {@link
	android.app.Activity#startActivity startActivity()}. For example:</p>

	<pre>
	Intent intent = new Intent(Intent.ACTION_SEND);
	...

	// Always use string resources for UI text. This says something like "Share this photo with"
	String title = getResources().getText(R.string.chooser_title);
	// Create and start the chooser
	Intent chooser = Intent.createChooser(intent, title);
	startActivity(chooser);
	</pre>

	<p>This displays a dialog with a list of apps that respond to the intent passed to the {@link
	android.content.Intent#createChooser createChooser()} method and uses the supplied text as the
	dialog title.</p>