basics/intents/result.jd

page.title=Getting a Result from an Activity
parent.title=Interacting with Other Apps
parent.link=index.html

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previous.title=Sending the User to Another App
previous.link=sending.html
next.title=Allowing Other Apps to Start Your Activity
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@jd:body

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

<h2>This lesson teaches you to</h2>
<ol>
  <li><a href="#StartActivity">Start the Activity</a></li>
  <li><a href="#ReceiveResult">Receive the Result</a></li>
</ol>

<h2>You should also read</h2>
<ul>
    <li><a href="{@docRoot}training/sharing/index.html">Sharing Simple Data</a></li>
    <li><a href="{@docRoot}training/secure-file-sharing/index.html">Sharing Files</a>
</ul>

  </div>
</div>

<p>Starting another activity doesn't have to be one-way. You can also start another activity and
receive a result back. To receive a result, call {@link android.app.Activity#startActivityForResult
startActivityForResult()} (instead of {@link android.app.Activity#startActivity
startActivity()}).</p>

<p>For example, your app can start a camera app and receive the captured photo as a result. Or, you
might start the People app in order for the user to select a
contact and you'll receive the contact details as a result.</p>

<p>Of course, the activity that responds must be designed to return a result. When it does, it
sends the result as another {@link android.content.Intent} object. Your activity receives it in
the {@link android.app.Activity#onActivityResult onActivityResult()} callback.</p>

<p class="note"><strong>Note:</strong> You can use explicit or implicit intents when you call
{@link android.app.Activity#startActivityForResult startActivityForResult()}. When starting one of
your own activities to receive a result, you should use an explicit intent to ensure that you
receive the expected result.</p>


<h2 id="StartActivity">Start the Activity</h2>

<p>There's nothing special about the {@link android.content.Intent} object you use when starting
an activity for a result, but you do need to pass an additional integer argument to the {@link
android.app.Activity#startActivityForResult startActivityForResult()} method.</p>

<p>The integer argument is a "request code" that identifies your request. When you receive the
result {@link android.content.Intent}, the callback provides the same request code so that your
app can properly identify the result and determine how to handle it.</p>

<p>For example, here's how to start an activity that allows the user to pick a contact:</p>

<pre>
static final int PICK_CONTACT_REQUEST = 1;  // The request code
...
private void pickContact() {
    Intent pickContactIntent = new Intent(Intent.ACTION_PICK, Uri.parse("content://contacts"));
    pickContactIntent.setType(Phone.CONTENT_TYPE); // Show user only contacts w/ phone numbers
    startActivityForResult(pickContactIntent, PICK_CONTACT_REQUEST);
}
</pre>


<h2 id="ReceiveResult">Receive the Result</h2>

<p>When the user is done with the subsequent activity and returns, the system calls your activity's
{@link android.app.Activity#onActivityResult onActivityResult()} method. This method includes three
arguments:</p>

<ul>
  <li>The request code you passed to {@link
android.app.Activity#startActivityForResult startActivityForResult()}.</li>
  <li>A result code specified by the second activity. This is either {@link
android.app.Activity#RESULT_OK} if the operation was successful or {@link
android.app.Activity#RESULT_CANCELED} if the user backed out or the operation failed for some
reason.</li>
  <li>An {@link android.content.Intent} that carries the result data.</li>
</ul>

<p>For example, here's how you can handle the result for the "pick a contact" intent:</p>

<pre>
&#64;Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    // Check which request we're responding to
    if (requestCode == PICK_CONTACT_REQUEST) {
        // Make sure the request was successful
        if (resultCode == RESULT_OK) {
            // The user picked a contact.
            // The Intent's data Uri identifies which contact was selected.

            // Do something with the contact here (bigger example below)
        }
    }
}
</pre>

<p>In this example, the result {@link android.content.Intent} returned by
Android's Contacts or People app provides a content {@link android.net.Uri} that identifies the
contact the user selected.</p>

<p>In order to successfully handle the result, you must understand what the format of the result
{@link android.content.Intent} will be. Doing so is easy when the activity returning a result is
one of your own activities. Apps included with the Android platform offer their own APIs that
you can count on for specific result data. For instance, the People app (Contacts app on some older
versions) always returns a result with the content URI that identifies the selected contact, and the
Camera app returns a {@link android.graphics.Bitmap} in the {@code "data"} extra (see the class
about <a href="{@docRoot}training/camera/index.html">Capturing Photos</a>).</p>


<h4>Bonus: Read the contact data</h4>

<p>The code above showing how to get a result from the People app doesn't go into
details about how to actually read the data from the result, because it requires more advanced
discussion about <a href="{@docRoot}guide/topics/providers/content-providers.html">content
providers</a>. However, if you're curious, here's some more code that shows how to query the
result data to get the phone number from the selected contact:</p>

<pre>
&#64;Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    // Check which request it is that we're responding to
    if (requestCode == PICK_CONTACT_REQUEST) {
        // Make sure the request was successful
        if (resultCode == RESULT_OK) {
            // Get the URI that points to the selected contact
            Uri contactUri = data.getData();
            // We only need the NUMBER column, because there will be only one row in the result
            String[] projection = {Phone.NUMBER};

            // Perform the query on the contact to get the NUMBER column
            // We don't need a selection or sort order (there's only one result for the given URI)
            // CAUTION: The query() method should be called from a separate thread to avoid blocking
            // your app's UI thread. (For simplicity of the sample, this code doesn't do that.)
            // Consider using {@link android.content.CursorLoader} to perform the query.
            Cursor cursor = getContentResolver()
                    .query(contactUri, projection, null, null, null);
            cursor.moveToFirst();

            // Retrieve the phone number from the NUMBER column
            int column = cursor.getColumnIndex(Phone.NUMBER);
            String number = cursor.getString(column);

            // Do something with the phone number...
        }
    }
}
</pre>

<p class="note"><strong>Note:</strong> Before Android 2.3 (API level 9), performing a query
on the {@link android.provider.ContactsContract.Contacts Contacts Provider} (like the one shown
above) requires that your app declare the {@link
android.Manifest.permission#READ_CONTACTS} permission (see <a
href="{@docRoot}guide/topics/security/security.html">Security and Permissions</a>). However,
beginning with Android 2.3, the Contacts/People app grants your app a temporary
permission to read from the Contacts Provider when it returns you a result. The temporary permission
applies only to the specific contact requested, so you cannot query a contact other than the one
specified by the intent's {@link android.net.Uri}, unless you do declare the {@link
android.Manifest.permission#READ_CONTACTS} permission.</p>