training/camera/photobasics.jd

page.title=Taking Photos Simply
parent.title=Capturing Photos
parent.link=index.html

trainingnavtop=true
next.title=Recording Videos Simply
next.link=videobasics.html

@jd:body


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

    <h2>This lesson teaches you to</h2>
    <ol>
      <li><a href="#TaskManifest">Request Camera Permission</a></li>
      <li><a href="#TaskCaptureIntent">Take a Photo with the Camera App</a></li>
      <li><a href="#TaskPhotoView">View the Photo</a></li>
      <li><a href="#TaskPath">Save the Photo</a></li>
      <li><a href="#TaskGallery">Add the Photo to a Gallery</a></li>
      <li><a href="#TaskScalePhoto">Decode a Scaled Image</a></li>
    </ol>

    <h2>You should also read</h2>
    <ul>
      <li><a href="{@docRoot}guide/topics/media/camera.html">Camera</a></li>
      <li><a href="{@docRoot}guide/components/intents-filters.html">Intents and Intent
      Filters</a></li>
    </ul>

    <h2>Try it out</h2>
    <div class="download-box">
      <a href="http://developer.android.com/shareables/training/PhotoIntentActivity.zip"
class="button">Download the
sample</a>
      <p class="filename">PhotoIntentActivity.zip</p>
    </div>

  </div>
</div>

<p>This lesson explains how to capture photos using an existing camera
application.</p>

<p>Suppose you are implementing a crowd-sourced weather service that makes a
global weather map by blending together pictures of the sky taken by devices
running your client app. Integrating photos is only a small part of your
application. You want to take photos with minimal fuss, not reinvent the
camera. Happily, most Android-powered devices already have at least one camera
application installed. In this lesson, you learn how to make it take a picture
for you.</p>


<h2 id="TaskManifest">Request Camera Permission</h2>

<p>If an essential function of your application is taking pictures, then restrict
its visibility on Google Play to devices that have a camera.  To advertise
that your application depends on having a camera, put a <a
href="{@docRoot}guide/topics/manifest/uses-feature-element.html"> {@code
&lt;uses-feature&gt;}</a> tag in your manifest file:</p>

<pre>
&lt;manifest ... >
    &lt;uses-feature android:name="android.hardware.camera" /&gt;
    ...
&lt;/manifest ... >
</pre>

<p>If your application uses, but does not require a camera in order to function, add {@code
android:required="false"} to the tag. In doing so, Google Play will allow devices without a
camera to download your application. It's then your responsibility to check for the availability
of the camera at runtime by calling {@link
android.content.pm.PackageManager#hasSystemFeature hasSystemFeature(PackageManager.FEATURE_CAMERA)}.
If a camera is not available, you should then disable your camera features.</p>


<h2 id="TaskCaptureIntent">Take a Photo with the Camera App</h2>

<p>The Android way of delegating actions to other applications is to invoke an {@link
android.content.Intent} that describes what you want done. This process involves three pieces: The
{@link android.content.Intent} itself, a call to start the external {@link android.app.Activity},
and some code to handle the image data when focus returns to your activity.</p>

<p>Here's a function that invokes an intent to capture a photo.</p>

<pre>
private void dispatchTakePictureIntent(int actionCode) {
    Intent takePictureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
    startActivityForResult(takePictureIntent, actionCode);
}
</pre>


<p>Congratulations: with this code, your application has gained the ability to
make another camera application do its bidding! Of course, if no compatible
application is ready to catch the intent, then your app will fall down like a
botched stage dive. Here is a function to check whether an app can handle your intent:</p>

<pre>
public static boolean isIntentAvailable(Context context, String action) {
    final PackageManager packageManager = context.getPackageManager();
    final Intent intent = new Intent(action);
    List&lt;ResolveInfo> list =
            packageManager.queryIntentActivities(intent, PackageManager.MATCH_DEFAULT_ONLY);
    return list.size() > 0;
}
</pre>


<h2 id="TaskPhotoView">View the Photo</h2>

<p>If the simple feat of taking a photo is not the culmination of your app's
ambition, then you probably want to get the image back from the camera
application and do something with it.</p>

<p>The Android Camera application encodes the photo in the return {@link android.content.Intent}
delivered to {@link android.app.Activity#onActivityResult onActivityResult()} as a small {@link
android.graphics.Bitmap} in the extras, under the key {@code "data"}. The following code retrieves
this image and displays it in an {@link android.widget.ImageView}.</p>

<pre>
private void handleSmallCameraPhoto(Intent intent) {
    Bundle extras = intent.getExtras();
    mImageBitmap = (Bitmap) extras.get("data");
    mImageView.setImageBitmap(mImageBitmap);
}
</pre>

<p class="note"><strong>Note:</strong> This thumbnail image from {@code "data"} might be good for an
icon, but not a lot more. Dealing with a full-sized image takes a bit more
work.</p>


<h2 id="TaskPath">Save the Photo</h2>

<p>The Android Camera application saves a full-size photo if you give it a file to
save into. You must provide a path that includes the storage volume,
folder, and file name.</p>

<p>There is an easy way to get the path for photos, but it works only on Android 2.2 (API level 8)
and later:</p>

<pre>
storageDir = new File(
    Environment.getExternalStoragePublicDirectory(
        Environment.DIRECTORY_PICTURES
    ),
    getAlbumName()
);
</pre>

<p>For earlier API levels, you have to provide the name of the photo
directory yourself.</p>

<pre>
storageDir = new File (
    Environment.getExternalStorageDirectory()
        + PICTURES_DIR
        + getAlbumName()
);
</pre>

<p class="note"><strong>Note:</strong> The path component {@code PICTURES_DIR} is
just {@code Pictures/}, the standard location for shared photos on the external/shared
storage.</p>


<h3 id="TaskFileName">Set the file name</h3>

<p>As shown in the previous section, the file location for an image should be
driven by the device environment. What you need to do yourself is choose a
collision-resistant file-naming scheme. You may wish also to save the path in a
member variable for later use. Here's an example solution:</p>

<pre>
private File createImageFile() throws IOException {
    // Create an image file name
    String timeStamp =
        new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());
    String imageFileName = JPEG_FILE_PREFIX + timeStamp + "_";
    File image = File.createTempFile(
        imageFileName,
        JPEG_FILE_SUFFIX,
        getAlbumDir()
    );
    mCurrentPhotoPath = image.getAbsolutePath();
    return image;
}
</pre>


<h3 id="TaskIntentFileName">Append the file name onto the Intent</h3>

<p>Once you have a place to save your image, pass that location to the camera
application via the {@link android.content.Intent}.</p>

<pre>
File f = createImageFile();
takePictureIntent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(f));
</pre>


<h2 id="TaskGallery">Add the Photo to a Gallery</h2>

<p>When you create a photo through an intent, you should know where your image is located, because
you said where to save it in the first place.  For everyone else, perhaps the easiest way to make
your photo accessible is to make it accessible from the system's Media Provider.</p>

<p>The following example method demonstrates how to invoke the system's media scanner to add your
photo to the Media Provider's database, making it available in the Android Gallery application
and to other apps.</p>

<pre>
private void galleryAddPic() {
    Intent mediaScanIntent = new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE);
    File f = new File(mCurrentPhotoPath);
    Uri contentUri = Uri.fromFile(f);
    mediaScanIntent.setData(contentUri);
    this.sendBroadcast(mediaScanIntent);
}
</pre>


<h2 id="TaskScalePhoto">Decode a Scaled Image</h2>

<p>Managing multiple full-sized images can be tricky with limited memory. If
you find your application running out of memory after displaying just a few
images, you can dramatically reduce the amount of dynamic heap used by
expanding the JPEG into a memory array that's already scaled to match the size
of the destination view. The following example method demonstrates this
technique.</p>

<pre>
private void setPic() {
    // Get the dimensions of the View
    int targetW = mImageView.getWidth();
    int targetH = mImageView.getHeight();

    // Get the dimensions of the bitmap
    BitmapFactory.Options bmOptions = new BitmapFactory.Options();
    bmOptions.inJustDecodeBounds = true;
    BitmapFactory.decodeFile(mCurrentPhotoPath, bmOptions);
    int photoW = bmOptions.outWidth;
    int photoH = bmOptions.outHeight;

    // Determine how much to scale down the image
    int scaleFactor = Math.min(photoW/targetW, photoH/targetH);

    // Decode the image file into a Bitmap sized to fill the View
    bmOptions.inJustDecodeBounds = false;
    bmOptions.inSampleSize = scaleFactor;
    bmOptions.inPurgeable = true;

    Bitmap bitmap = BitmapFactory.decodeFile(mCurrentPhotoPath, bmOptions);
    mImageView.setImageBitmap(bitmap);
}
</pre>