docs/html/preview/features/runtime-permissions.jd

page.title=Permissions
page.tags=previewresources, androidm
page.keywords=permissions, runtime, preview
page.image=images/permissions_check.png
@jd:body


<div id="qv-wrapper">
  <div id="qv">
    <h2>Quickview</h2>
    <ul>
      <li>If your app targets the M Preview SDK, it prompts users to grant
        permissions at runtime, instead of install time.</li>
      <li>Users can revoke permissions at any time from the app Settings
        screen.</li>
      <li>Your app needs to check that it has the permissions it needs every
        time it runs.</li>
    </ul>

    <h2>In this document</h2>
    <ol>
      <li><a href="#overview">Overview</a></li>
      <li><a href="#coding">Coding for Runtime Permissions</a></li>
      <li><a href="#testing">Testing Runtime Permissions</a></li>
      <li><a href="#best-practices">Best Practices and Usage Notes</a></li>
    </ol>

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  <h2>Related Samples</h2>
  <ol>
    <li></li>
  </ol>
-->

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  <h2>See also</h2>
  <ol>
    <li>
    </li>
  </ol>
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  </div> <!-- qv -->
</div> <!-- qv-wrapper -->

<!-- video box -->
<a class="notice-developers-video"
    href="https://www.youtube.com/watch?v=f17qe9vZ8RM">
<div>
    <h3>Video</h3>
    <p>Google I/O 2015—Android M Permissions: Best Practices for
      Developers</p>
</div>
</a>

<p>
  The M Developer Preview introduces a new app permissions model which
  streamlines the process for users to install and upgrade apps. If an app
  running on the M Preview supports the new permissions model, the user does not have to
  grant any permissions when they install or upgrade the app. Instead, the app
  requests permissions as it needs them, and the system shows a dialog to the
  user asking for the permission.
</p>

<p>
  If an app supports the new permissions model, it can still be installed and
  run on devices running older versions of Android, using the old permissions
  model on those devices.
</p>

<h2 id="overview">
  Overview
</h2>

<p>
  With the M Developer Preview, the platform introduces a new app permissions
  model. Here's a summary of the key components of this new model:
</p>

<ul>
  <li>
    <strong>Declaring Permissions:</strong> The app declares all the
    permissions it needs in the manifest, as in earlier Android platforms.
  </li>

  <li>
    <strong>Permission Groups:</strong> Permissions are divided into
    <em>permission groups</em>, based on their functionality. For example, the
    <code>CONTACTS</code> permission group contains permissions to read and
    write the user's contacts and profile information.
  </li>

  <li>
    <p><strong>Limited Permissions Granted at Install Time:</strong> When the
    user installs or updates the app, the system grants the app all
    permissions listed in the manifest that fall under {@link
    android.content.pm.PermissionInfo#PROTECTION_NORMAL PROTECTION_NORMAL}.
    For example, alarm clock and internet permissions fall under {@link
    android.content.pm.PermissionInfo#PROTECTION_NORMAL PROTECTION_NORMAL}, so
    they are automatically granted at install time. For more information about
    how normal permissions are handled, see <a href="#normal">Normal
    Permissions</a>.
    </p>

    <p>The system may also grant the app signature permissions, as
    described in <a href="#system-apps">System components and signature
    permissions</a>. The user is <em>not</em> prompted to grant any permissions
    at install time.</p>
  </li>

  <li>
    <strong>User Grants Permissions at Run-Time:</strong> When the app requests
    a permission, the system shows a dialog to the user, then calls the app's
    callback function to notify it whether the user granted the permission.
  </li>

</ul>

<p>
  This permission model changes the way your app behaves for features that
  require permissions. Here's a summary of the development practices you should
  follow to adjust to this model:
</p>

<ul>

  <li>
    <strong>Always Check for Permissions:</strong> When the app needs to
    perform any action that requires a permission, it should first check
    whether it has that permission already. If it does not, it requests to be
    granted that permission. You do not need to check for permissions that
    fall under {@link
    android.content.pm.PermissionInfo#PROTECTION_NORMAL PROTECTION_NORMAL}.
  </li>

  <li>
    <strong>Handle Lack of Permissions Gracefully:</strong> If the app is not
    granted an appropriate permission, it should handle the failure cleanly.
    For example, if the permission is just needed for an added feature, the app
    can disable that feature. If the permission is essential for the app to
    function, the app might disable all its functionality and inform the user
    that they need to grant that permission.
  </li>

  <div class="figure" style="width:220px" id="fig-perms-screen">
    <img src="images/app-permissions-screen_2x.png"
    srcset="images/app-permissions-screen.png 1x, images/app-permissions-screen_2x.png 2x"
    alt="" width="220">
    <p class="img-caption">
      <strong>Figure 1.</strong> Permission screen in the app's Settings.
    </p>
  </div>

  <li>
    <strong>Permissions are Revocable:</strong> Users can revoke an app's
    permissions at any time. If a user turns off an app's permissions, the app
    is <em>not</em> notified. Once again, your app should verify that it has
    needed permissions before performing any restricted actions.
  </li>
</ul>

<p class="note">
  <strong>Note:</strong> If an app targets the M Developer Preview, it
  <em>must</em> use the new permissions model.
</p>

<p>
  As of the launch of the M Developer Preview, not all Google apps fully
  implement the new permissions model. Google is updating these apps over
  the course of the M Developer Preview to properly respect Permissions toggle
  settings.
</p>

<p class="note">
  <strong>Note:</strong> If your app has its own API surface, do not proxy
  permissions without first ensuring the caller has the requisite permissions
  to access that data.
</p>

<h3 id="perm-groups">Permission groups</h3>

<p>
  Related permissions are divided into <em>permission groups</em> to
  allow users to grant related permissions to an app in a single action.
  The user only has to grant permission once per app for each permission group.
  If the app subsequently requests a permission from the same permission
  group, the system automatically grants the permission without any action from
  the user. The system calls your app's <code>onRequestPermissionsResult()</code>
  method just as if the user had granted permission through the dialog box.
</p>

<p>
  For example, suppose an app lists in its manifest that it needs the
  <code>SEND_SMS</code> and <code>RECEIVE_SMS</code> permissions, which both
  belong to <code>android.permission-group.SMS</code>. When the app needs to
  send a message, it requests the <code>SEND_SMS</code> permission. The system
  shows the user a dialog box asking if the app can have access to SMS. If the
  user agrees, the system grants the app the <code>SEND_SMS</code> permission it
  requested. Later, the app requests <code>RECEIVE_SMS</code>. The
  system automatically grants this permission, since the user had already
  approved a permission in the same permission group.
</p>

<h3 id="system-apps">
  System components and signature permissions
</h3>

<p>
  Ordinarily, when the user installs an app, the system only grants the app the
  permissions listed in the manifest that fall under
  {@link android.content.pm.PermissionInfo#PROTECTION_NORMAL
  PROTECTION_NORMAL}. However, under some circumstances the system grants the
  app more permissions:
</p>

<ul>
  <li>System components automatically receive all
  the permissions listed in their manifests.
  </li>

  <li>If the app requests permissions in the manifest that fall under {@link
  android.content.pm.PermissionInfo#PROTECTION_SIGNATURE PROTECTION_SIGNATURE},
  and the app is signed with the same certificate as the app that declared
  those permissions, the system grants the requesting app those permissions on
  installation. Apps cannot request signature permissions at runtime.</li>
</ul>

<h3 id="compatibility">
  Forwards and backwards compatibility
</h3>

<p>
  If an app does not target the M Developer Preview, the app continues to use
  the old permissions model even on M Preview devices. When the user installs
  the app, the system asks the user to grant all permissions listed in the
  app's manifest.
</p>

<p class="note">
  <strong>Note:</strong> On devices running the M Developer Preview, a user can
  turn off permissions for any app (including legacy apps) from the app's
  Settings screen. If a user turns off permissions for a legacy app, the system
  silently disables the appropriate functionality. When the app attempts to
  perform an operation that requires that permission, the operation will not
  necessarily cause an exception. Instead, it might return an empty data set,
  signal an error, or otherwise exhibit unexpected behavior. For example, if you
  query a calendar without permission, the method returns an empty data set.
</p>

<p>
  If you install an app using the new permissions model on a device that is not
  running the M Preview,
  the system treats it the same as any other app: the system asks
  the user to grant all declared permissions at install time.
</p>

<p class="note">
  <strong>Note:</strong> For the preview release, you must set the minimum SDK
  version to the M Preview SDK to compile with the preview SDK. This means you
  will not be able to test such apps on older platforms during the developer
  preview.
</p>

<h3 id="perms-vs-intents">Permissions versus intents</h3>

<p>
  In many cases, you can choose between two ways for your app to perform a
  task. You can have your app ask for permission to perform the operation
  itself. Alternatively, you can have the app use an intent to have another app
  perform the task.
</p>

<p>
  For example, suppose your app needs to be able to take pictures with the
  device camera. Your app can request the
  <code>android.permission.CAMERA</code> permission, which allows your app to
  access the camera directly. Your app would then use the camera APIs
  to control the camera and take a picture. This approach gives your app full
  control over the photography process, and lets you incorporate the camera UI
  into your app.
</p>

<p>
  However, if you don't need such control, you can just use an {@link
  android.provider.MediaStore#ACTION_IMAGE_CAPTURE ACTION_IMAGE_CAPTURE} intent
  to request an image. When you start the intent, the user is prompted to
  choose a camera app (if there isn't already a default camera app), and that
  app takes the picture. The camera app returns the picture to your app's {@link
  android.app.Activity#onActivityResult onActivityResult()} method.
</p>

<p>
  Similarly, if you need to make a phone call, access the user's contacts, and
  so on, you can do that by creating an appropriate intent, or you can request
  the permission and access the appropriate objects directly. There are
  advantages and disadvantages to each approach.
</p>

<p>
  If you use permissions:
</p>

<ul>
  <li>Your app has full control over the user experience when you perform the
  operation. However, such broad control adds to the complexity of your task,
  since you need to design an appropriate UI.
  </li>

  <li>The user is prompted to give permission once, the first time you perform
  the operation. After that, your app can perform the operation without
  requiring additional interaction from the user. However, if the user doesn't
  grant the permission (or revokes it later on), your app becomes unable to
  perform the operation at all.
  </li>
</ul>

<p>
  If you use an intent:
</p>

<ul>
  <li>You do not have to design the UI for the operation. The app that handles
  the intent provides the UI. However, this means you have
  no control over the user experience. The user could be interacting with an
  app you've never seen.
  </li>

  <li>If the user does not have a default app for the operation, the system
  prompts the user to choose an app. If the user does not designate a default
  handler, they may have to go
  through an extra dialog every time they perform the operation.
  </li>
</ul>

<h2 id="coding">Coding for Runtime Permissions</h2>

<p>
  If your app targets the new M Developer Preview, you must use the new
  permissions model. This means that in addition to declaring your needed
  permissions in the manifest, you must also check to see if you have the
  permissions at run time, and request the permissions if you do not already
  have them.
</p>

<h3 id="enabling">
  Enabling the new permissions model
</h3>

<p>
  To enable the new M Developer Preview permissions model, set the app's
  <code>targetSdkVersion</code> attribute to <code>"MNC"</code>, and
  <code>compileSdkVersion</code> to <code>"android-MNC"</code>. Doing so
  enables all the new permissions features.
</p>

<p>
  For the preview release, you must set <code>minSdkVersion</code> to
  <code>"MNC"</code> to compile with the preview SDK.
</p>

<h3 id="m-only-perm">
  Designating a permission for the M Preview only
</h3>

<p>
  You can use the new <code>&lt;uses-permission-sdk-m&gt;</code> element in the app manifest
  to indicate that a permission is only needed on the M Developer Preview. If
  you declare a permission this way, then whenever the app is installed on an
  older device, the system does not prompt the user or grant the
  permission to the app. By using the <code>&lt;uses-permission-sdk-m&gt;</code>
  element, you can add new permissions
  to updated versions of your app without forcing users to grant permissions
  when they install the update.
</p>

<p>
  If the app is running on a device with the M Developer Preview,
  <code>&lt;uses-permission-sdk-m&gt;</code> behaves the same as
  <code><a href="{@docRoot}guide/topics/manifest/uses-permission-element.html">&lt;uses-permission&gt;</a></code>.
  The system does not prompt the user to grant any permissions when they install
  the app, and the app requests permissions as they are needed.
</p>

<h3 id="prompting">
  Prompting for permissions
</h3>

<p>
  If your app uses the new M Developer Preview permissions model, the user is
  not asked to grant all permissions when the app is first launched on a device
  running the M Preview. Instead, your app requests permissions as they are
  needed. When your app requests a permission, the system shows a dialog to the
  user.
</p>

<p>
  If your app runs on a device that has SDK 22 or lower, the app uses the old
  permissions model. When the user installs the app, they are prompted to grant
  all the permissions your app requests in its manifest, except for those
  permissions which are labeled with <code>&lt;uses-permission-sdk-m&gt;</code>.
</p>

<h4 id="check-platform">Check what platform the app is running on</h4>

<p>
  This permissions model is only supported on devices running the M Developer
  Preview. Before calling any of these methods, the app should verify
  what platform it's running on
  by checking the value of {@link android.os.Build.VERSION#CODENAME
  Build.VERSION.CODENAME}. If the device is running the M Developer Preview,
  {@link android.os.Build.VERSION#CODENAME CODENAME} is <code>"MNC"</code>.
</p>

<h4 id="check-for-permission">Check if the app has the needed permission</h4>

<p>When the user tries to do something that requires a permission, the app
  checks to see if it currently has permission to perform this operation. To do
  this, the app calls
  <code>Context.checkSelfPermission(<i>permission_name</i>)</code>. The app
  should perform this check even if it knows the user has already granted that
  permission,
  since the user can revoke an app's permissions at any time. For example, if a
  user wants to use an app to take a picture, the app calls
  <code>Context.checkSelfPermission(Manifest.permission.CAMERA)</code>.</p>

<p class="table-caption" id="permission-groups">
  <strong>Table 1.</strong> Permissions and permission groups.</p>
<table>
  <tr>
    <th scope="col">Permission Group</th>
    <th scope="col">Permissions</th>
  </tr>

  <tr>
    <td><code>android.permission-group.CALENDAR</code></td>
    <td>
      <ul>
        <li>
          <code>android.permission.READ_CALENDAR</code>
        </li>
      </ul>
      <ul>
        <li>
          <code>android.permission.WRITE_CALENDAR</code>
        </li>
      </ul>
    </td>
  </tr>

  <tr>
    <td><code>android.permission-group.CAMERA</code></td>
    <td>
      <ul>
        <li>
          <code>android.permission.CAMERA</code>
        </li>
      </ul>
    </td>
  </tr>

  <tr>
    <td><code>android.permission-group.CONTACTS</code></td>
    <td>
      <ul>
        <li>
          <code>android.permission.READ_CONTACTS</code>
        </li>
        <li>
          <code>android.permission.WRITE_CONTACTS</code>
        </li>
        <li>
          <code>android.permission.READ_PROFILE</code>
        </li>
        <li>
          <code>android.permission.WRITE_PROFILE</code>
        </li>
      </ul>
    </td>
  </tr>

  <tr>
    <td><code>android.permission-group.LOCATION</code></td>
    <td>
      <ul>
        <li>
          <code>android.permission.ACCESS_FINE_LOCATION</code>
        </li>
        <li>
          <code>android.permission.ACCESS_COARSE_LOCATION</code>
        </li>
      </ul>
    </td>
  </tr>

  <tr>
    <td><code>android.permission-group.MICROPHONE</code></td>
    <td>
      <ul>
        <li>
          <code>android.permission.RECORD_AUDIO</code>
        </li>
      </ul>
    </td>
  </tr>

  <tr>
    <td><code>android.permission-group.PHONE</code></td>
    <td>
      <ul>
        <li>
          <code>android.permission.READ_PHONE_STATE</code>
        </li>
        <li>
          <code>android.permission.CALL_PHONE</code>
        </li>
        <li>
          <code>android.permission.READ_CALL_LOG</code>
        </li>
        <li>
          <code>android.permission.WRITE_CALL_LOG</code>
        </li>
        <li>
          <code>com.android.voicemail.permission.ADD_VOICEMAIL</code>
        </li>
        <li>
          <code>android.permission.USE_SIP</code>
        </li>
        <li>
          <code>android.permission.PROCESS_OUTGOING_CALLS</code>
        </li>
      </ul>
    </td>
  </tr>

  <tr>
    <td><code>android.permission-group.SENSORS</code></td>
    <td>
      <ul>
        <li>
          <code>android.permission.BODY_SENSORS</code>
        </li>
      </ul>
      <ul>
        <li>
          <code>android.permission.USE_FINGERPRINT</code>
        </li>
      </ul>
    </td>
  </tr>

  <tr>
    <td><code>android.permission-group.SMS</code></td>
    <td>
      <ul>
        <li>
          <code>android.permission.SEND_SMS</code>
        </li>
        <li>
          <code>android.permission.RECEIVE_SMS</code>
        </li>
        <li>
          <code>android.permission.READ_SMS</code>
        </li>
        <li>
          <code>android.permission.RECEIVE_WAP_PUSH</code>
        </li>
        <li>
          <code>android.permission.RECEIVE_MMS</code>
        </li>
        <li>
          <code>android.permission.READ_CELL_BROADCASTS</code>
        </li>
      </ul>
    </td>
  </tr>

  <tr>
    <td>
      <code>android.permission-group.STORAGE</code>
    </td>
    <td>
      <ul>
        <li>
          <code>android.permission.READ_EXTERNAL_STORAGE</code>
        </li>
        <li>
          <code>android.permission.WRITE_EXTERNAL_STORAGE</code>
        </li>
      </ul>
    </td>
  </tr>

</table>

<h4 id="explain-need">Explain why the app needs permissions</h4>

<p>
  In some circumstances, you might want to help the user understand why your
  app needs a permission. For example, if a user launches a photography app,
  the user probably won't be surprised that the app asks for permission to use
  the camera. But if the user turns down that permission request, then launches
  the photography app again, that might indicate that the user needs some help
  understanding why the permission is needed.
</p>

<p>
  To help find the situations where you need to provide extra explanation, the
  system provides the
  <code>Activity.shouldShowRequestPermissionRationale(String)</code>
  method. This
  method returns <code>true</code> if the app has requested this permission
  previously and the user denied the request.
  That indicates that you should probably explain to the
  user why you need the permission.
</p>

<p>
  If the user turned down the permission request in the
  past and chose the <em>Don't ask again</em> option in the permission request system
  dialog, this method returns <code>false</code>. The method also returns
  <code>false</code> if the device policy prohibits the app from having that
  permission.
</p>

<h4 id="request-permissions">Request permissions if necessary</h4>

<p>If the app doesn't already have the permission it needs, the app calls the
  <code>Activity.requestPermissions(String[], int)</code> method to
  request the appropriate permission or permissions. The app passes the
  permission or permissions it wants, and also an integer "request code".
  This method functions asynchronously: it returns right away, and after
  the user responds to the dialog box, the system calls the app's callback
  method with the results, passing the same "request code" that the app passed
  to <code>requestPermissions()</code>.</p>

  <p>The following code code checks if the app has permission to read the
    user's contacts, and requests the permission if necessary:</p>

<pre>
if (checkSelfPermission(Manifest.permission.READ_CONTACTS)
        != PackageManager.PERMISSION_GRANTED) {

    // Should we show an explanation?
    if (shouldShowRequestPermissionRationale(
            Manifest.permission.READ_CONTACTS)) {
        // Explain to the user why we need to read the contacts
    }

    requestPermissions(new String[]{Manifest.permission.READ_CONTACTS},
            MY_PERMISSIONS_REQUEST_READ_CONTACTS);

    // MY_PERMISSIONS_REQUEST_READ_CONTACTS is an
    // app-defined int constant

    return;
}
</pre>

<h4 id="handle-response">Handle the permissions request response</h4>

<p>
  When an app requests permissions, the system presents a dialog box to the
  user. When the user responds, the system invokes your app's
  <code>Activity.onRequestPermissionsResult(int, String[], int[])</code>
  passing it the user response. Your app needs to override that method. The
  callback is passed the same request code you passed to
  <code>requestPermissions()</code>. For example, if an app requests
  <code>READ_CONTACTS</code> access it might have the following callback
  method:
</p>

<pre>
&#64;Override
public void onRequestPermissionsResult(int requestCode,
        String permissions[], int[] grantResults) {
    switch (requestCode) {
        case MY_PERMISSIONS_REQUEST_READ_CONTACTS: {
            if (grantResults[0] == PackageManager.PERMISSION_GRANTED) {

                // permission was granted, yay! do the
                // calendar task you need to do.

            } else {

                // permission denied, boo! Disable the
                // functionality that depends on this permission.
            }
            return;
        }

        // other 'switch' lines to check for other
        // permissions this app might request
    }
}
</pre>

<p>
  If the user denies a permission request, your app should take appropriate
  action. For example, your app might show a dialog explaining why it could not
  perform the user's original request.
</p>

<p>
  When the system asks the user to grant a permission, the user has the option
  of telling the system not to ask for that permission again. In that case,
  when an app uses <code>requestPermissions()</code> to ask for that permission,
  the system immediately denies the request. In this case, the system calls
  your <code>onRequestPermissionsResult()</code> the same way it would if the
  user had explicitly rejected your request again. For this reason, your app
  cannot assume that any direct interaction with the user has taken place.
</p>

<h2 id="testing">Testing Runtime Permissions</h2>

<p>
  If your app targets the M Developer Preview, you must test that it
  handles permissions properly. You cannot assume that your app has any
  particular permissions when it runs. When the app is first launched, it is
  likely to have no permissions, and the user can revoke or restore permissions
  at any time.
</p>

<p>
  You should test your app to make sure it behaves properly under all
  permission situations. With the M Preview SDK, we have provided new
  <a href="{@docRoot}tools/help/adb.html">Android
  Debug Bridge (adb)</a> commands to enable you to test your app with whatever
  permissions settings you need to try.
</p>

<h3>
  New adb commands and options
</h3>

<p>
  The M Preview SDK Platform-tools provides several new commands to let you test
  how your app handles permissions.
</p>

<h4>
  Install with permissions
</h4>

<p>
  You can use the <a href="{@docRoot}tools/help/adb.html#move"><code>adb
  install</code></a> command's new <code>-g</code> option, which installs the
  app and grants all permissions listed in its manifest:
</p>

<pre class="no-pretty-print">
$ adb install -g &lt;path_to_apk&gt;
</pre>

<h4>
  Grant and revoke permissions
</h4>

<p>
  You can use new ADB <a href="{@docRoot}tools/help/adb.html#pm">package manager
  (pm)</a> commands to grant and revoke permissions to an installed app.
  This functionality can be useful for automated testing.
</p>

<p>
  To grant a permission, use the package manager's <code>grant</code> command:
</p>

<pre class="no-pretty-print">
$ adb pm grant &lt;package_name&gt; &lt;permission_name&gt;
</pre>

<p>
  For example, to grant the com.example.myapp package permission to record
  audio, use this command:
</p>

<pre class="no-pretty-print">
$ adb pm grant com.example.myapp android.permission.RECORD_AUDIO
</pre>

<p>
  To revoke a permission, use the package manager's <code>revoke</code> command:
</p>

<pre class="no-pretty-print">
$ adb pm revoke &lt;package_name&gt; &lt;permission_name&gt;
</pre>

<h2 id="best-practices">Best Practices and Usage Notes</h2>

<p>
  The new permissions model gives users a smoother experience, and makes it
  easier for them to install apps and feel comfortable with what the apps are
  doing. We recommend the following best practices to take full advantage of
  the new model.
</p>


<h3 id="bp-what-you-need">Only ask for permissions you need</h3>

<p>
  Every time you ask for a permission, you force the user to make a decision.
  If the user turns down the request, that reduces your app's functionality.
  You should minimize the number of times you make these requests.
</p>

<p>
  For example, quite often your app can get needed functionality by using an
  <a href="{@docRoot}guide/components/intents-filters.html">intent</a> instead
  of asking for permissions. If your app needs to take pictures with the
  phone's camera, your app can use a {@link
  android.provider.MediaStore#ACTION_IMAGE_CAPTURE
  MediaStore.ACTION_IMAGE_CAPTURE} intent. When your app executes the intent, the
  system prompts the user to choose an already-installed camera app to take the
  picture.
</p>

<h3 id="bp-dont-overwhelm">
  Don't overwhelm the user
</h3>

<p>
  If you confront the user with a lot of requests for permissions at once, you may
  overwhelm the user and cause them to quit your app. Instead, you should ask
  for permissions as you need them.
</p>

<p>
  In some cases, one or more permissions might be absolutely essential to your
  app. In that case, it might make sense to ask for all the permissions as soon
  as the app launches. For example, if you make a photography app, the app
  would need access to the device camera. When the user launches the app for
  the first time, they won't be surprised to be asked for permission to use
  the camera. But if the same app also had a feature to share photos with the
  user's contacts, you probably should <em>not</em> ask for that permission at
  first launch. Instead, wait until the user tries to use the "sharing" feature
  and ask for the permission then.
</p>

<p>
  If your app provides a tutorial, it may make sense to request the app's essential
  permissions at the end of the tutorial sequence.
</p>

<h3 id="bp-explain">
  Explain why you need permissions
</h3>

<p>
  The permissions dialog shown by the system when you call
  <code>requestPermissions()</code> says what permission your app wants, but
  doesn't say why. In some cases, the user may find that puzzling.
  It's a good idea to explain to the user why your app wants the permissions
  before calling <code>requestPermissions()</code>.
</p>

<p>
  For example, a photography app might want to use location services, so it can
  geotag the photos. A typical user might not understand that a photo can
  contain location information, and would be puzzled why their photography app
  wanted to know the location. So in this case, it's a good idea for the app to
  tell the user about this feature <em>before</em> calling
  <code>requestPermissions()</code>.
</p>

<p>
  One way to do this is to incorporate these requests into an app tutorial. The
  tutorial can show each of the app's features in turn, and as it does this, it
  can explain what permissions are needed. For example, the photography app's
  tutorial can demonstrate its "share photos with your contacts" feature, then
  tell the user that they need to give permission for the app to see the user's
  contacts. The app can then call <code>requestPermissions()</code> to ask the
  user for that access. Of course, not every user is going to follow the
  tutorial, so you still need to check for and request permissions during the
  app's normal operation.
</p>

<h3 id="normal">Normal Permissions</h3>

<p>
  Many permissions are designated as {@link
  android.content.pm.PermissionInfo#PROTECTION_NORMAL PROTECTION_NORMAL},
  which indicates that
  there's no great risk to the user's privacy or security in letting apps have
  those permissions. For example, users would reasonably want to know whether
  an app can read their contact information, so users have to grant this
  permission explicitly. By contrast, there's no great risk in allowing an app
  to vibrate the device, so that permission is designated as <em>normal.</em>
</p>

<p>
  If an app declares in its
  manifest that it needs a normal permission, the system automatically grants
  the app
  that permission at install time. The system does not prompt the user
  to grant normal
  permissions, and users cannot revoke these permissions.
</p>

<p>
  If your app declares that it needs normal permissions, the app does not need to
  call <code>Activity.checkSelfPermission()</code> or
  <code>Activity.requestPermissions()</code> for
  those permissions. Since you declared the permissions in the manifest, you
  can be sure your app was granted those permissions at install time.
</p>

<p>Currently, the following permissions are classified as {@link
    android.content.pm.PermissionInfo#PROTECTION_NORMAL PROTECTION_NORMAL}:</p>

<ul>
  <li><code>android.permission.ACCESS_LOCATION_EXTRA_COMMANDS</code></li>
  <li><code>android.permission.ACCESS_NETWORK_STATE</code></li>
  <li><code>android.permission.ACCESS_WIFI_STATE</code></li>
  <li><code>android.permission.ACCESS_WIMAX_STATE</code></li>
  <li><code>android.permission.BLUETOOTH</code></li>
  <li><code>android.permission.BLUETOOTH_ADMIN</code></li>
  <li><code>android.permission.BROADCAST_STICKY</code></li>
  <li><code>android.permission.CHANGE_NETWORK_STATE</code></li>
  <li><code>android.permission.CHANGE_WIFI_MULTICAST_STATE</code></li>
  <li><code>android.permission.CHANGE_WIFI_STATE</code></li>
  <li><code>android.permission.DISABLE_KEYGUARD</code></li>
  <li><code>android.permission.EXPAND_STATUS_BAR</code></li>
  <li><code>android.permission.FLASHLIGHT</code></li>
  <li><code>android.permission.GET_ACCOUNTS</code></li>
  <li><code>android.permission.GET_PACKAGE_SIZE</code></li>
  <li><code>android.permission.INTERNET</code></li>
  <li><code>android.permission.KILL_BACKGROUND_PROCESSES</code></li>
  <li><code>android.permission.MODIFY_AUDIO_SETTINGS</code></li>
  <li><code>android.permission.NFC</code></li>
  <li><code>android.permission.PERSISTENT_ACTIVITY</code></li>
  <li><code>android.permission.READ_SYNC_SETTINGS</code></li>
  <li><code>android.permission.READ_SYNC_STATS</code></li>
  <li><code>android.permission.READ_USER_DICTIONARY</code></li>
  <li><code>android.permission.RECEIVE_BOOT_COMPLETED</code></li>
  <li><code>android.permission.REORDER_TASKS</code></li>
  <li><code>android.permission.SET_TIME_ZONE</code></li>
  <li><code>android.permission.SET_WALLPAPER</code></li>
  <li><code>android.permission.SET_WALLPAPER_HINTS</code></li>
  <li><code>android.permission.SUBSCRIBED_FEEDS_READ</code></li>
  <li><code>android.permission.TRANSMIT_IR</code></li>
  <li><code>android.permission.VIBRATE</code></li>
  <li><code>android.permission.WAKE_LOCK</code></li>
  <li><code>android.permission.WRITE_SETTINGS</code></li>
  <li><code>android.permission.WRITE_SYNC_SETTINGS</code></li>
  <li><code>android.permission.WRITE_USER_DICTIONARY</code></li>
  <li><code>com.android.alarm.permission.SET_ALARM</code></li>
  <li><code>com.android.launcher.permission.INSTALL_SHORTCUT</code></li>
</ul>