tech/connect/block-numbers.html

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    <title>Implementing Block Phone Numbers</title>
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<p>
Because telephony is such an open communications channel - anyone may call or
text any number at any time - Android users need the ability to easily block
unwanted calls and texts.
</p>

<p>
Before N, Android users had to rely on downloaded apps to restrict calls and
texts from bothersome phone numbers. Many of those apps either do not work as
desired or provide a less-than ideal experience because there are no proper APIs
for blocking calls and messages.
</p>

<p>
Some manufacturers might ship their own blocking solutions out-of-the-box, but
if users switch devices, they may lose the blocked list completely due to lack
of interoperability. Finally, even if users are employing dialing apps and
messaging clients that provide such functionality, they likely still have to
perform the block action in each app for the block to take effect for both
calling and texting.
</p>

<h2 id="features">Features</h2>

<p>
The Android 7.0 release introduces a <code>BlockedNumberProvider</code> content
provider that stores a list of phone numbers the user has specified should not
be able to contact them via telephony communications (calls, SMS, MMS). The
system will respect the numbers in the blocked list by restricting calls and
texts from those numbers. Android 7.0 displays the list of blocked numbers and
allows the user to add and remove numbers.
</p>

<p>
Further, the number-blocking feature enables the system and the relevant apps on
the platform to work together to help protect the user and to simplify the
experience. The default dialer, default messaging client, UICC-privileged app,
and apps with the same signature as the system can all directly read from and
write to the blocked list. Because the blocked numbers are stored on the system,
no matter what dialing or messaging apps the user employs, the numbers stay
blocked. Finally, the blocked numbers list may be restored on any new device,
regardless of the manufacturer.
</p>

<ul>
<li>User will be guaranteed to have a blocking feature that works out-of-the-box
and will not lose their block list when they switch apps or get a new phone. All
relevant apps on the system can share the same list to provide the user with the
most streamlined experience.
<li>App developers do not need to develop their own way to manage a block list
and the calls and messages that come in. They can simply use the
platform-provided feature.
<li>Dialer / messenger apps that are selected as the default by the user can
read and write to the provider. Other apps can launch the block list management
user interface by using <code>createManageBlockedNumbersIntent()</code>
<li>OEMs can use platform provided feature to ship a blocking feature
out-of-the-box. OEMs can rest assured that when users switch from another OEMs
device that they have a better onboarding experience because the block list will
be transferred as well.
<li>If carrier has their own dialer or messenger app, they can reuse platform
feature for allowing the user to maintain a block list. They can rest assured
that the users block list can stay with the users, even when they get a new
device. Finally, all carrier-privileged apps can read the block list, so if the
carrier wants to provide some additional more powerful blocking for the user
based on the block list, that is now possible with this feature.</li></ul>

<h2 id="data-flow">Data flow</h2>

<img src="/devices/tech/connect/images/block-numbers-flow.png" alt="block numbers data flow" id="block-numbers-flow" />
<p class="img-caption">
  <strong>Figure 1.</strong> Block phone numbers data flow
</p>

<h2 id="examples-and-source">Examples and source</h2>

<p>
Here are example calls using the number-blocking new feature:
</p>

<h3 id="launch-from-app">Launch blocked number manager from app</h3>

<pre class="prettyprint">
Context.startActivity(telecomManager.createManageBlockedNumbersIntent(), null);
</pre>

<h3 id="query-blocked-numbers">Query blocked numbers</h3>

<pre class="prettyprint">
Cursor c = getContentResolver().query(BlockedNumbers.CONTENT_URI,
         new String[]{BlockedNumbers.COLUMN_ID,
         BlockedNumbers.COLUMN_ORIGINAL_NUMBER,
         BlockedNumbers.COLUMN_E164_NUMBER}, null, null, null);
</pre>

<h3 id="put-blocked-number">Put blocked number</h3>

<pre class="prettyprint">
ContentValues values = new ContentValues();
values.put(BlockedNumbers.COLUMN_ORIGINAL_NUMBER, "1234567890");
Uri uri = getContentResolver().insert(BlockedNumbers.CONTENT_URI, values);
</pre>

<h3 id="delete-blocked-number">Delete blocked number</h3>

<pre class="prettyprint">
ContentValues values = new ContentValues();
values.put(BlockedNumbers.COLUMN_ORIGINAL_NUMBER, "1234567890");
Uri uri = getContentResolver().insert(BlockedNumbers.CONTENT_URI, values);
getContentResolver().delete(uri, null, null);
</pre>

<h2 id="implementation">Implementation</h2>

<p>
These are the high-level tasks that must be completed to put the number-blocking
feature to use:
</p>

<ul>
<li>OEMs implement call/message-restriction features on their devices by using
<code>BlockedNumberProvider</code>
<li>If carrier has dialer or messenger application, implement call/message
restriction features by using <code>BlockedNumberProvider</code>
<li>Third-party dialer and messenger app vendors use
<code>BlockedNumberProvider</code> for their blocking features</li>
</ul>

<h3 id="recommendations-for-oems">Recommendations for OEMs</h3>

<p>
If the device had previously never shipped with any additional call/message
restriction features, use the number-blocking feature in the Android Open Source
Project (AOSP) on all such devices. It is recommended that reasonable entry
points for blocking are supported, such as blocking a number right from the call
log or within a message thread.
</p>

<p>
If the device had previously shipped with call/message restriction features,
adapt the features so all <em>strict-match phone numbers</em> that are blocked
are stored in the <code>BlockedNumberProvider,</code> and that the behavior
around the provider satisfy the requirements for this feature outlined in the
Android Compatibility Definition Document (CDD).
</p>

<p>
Any other advanced feature can be implemented via custom providers and custom UI
/ controls, as long as the CDD requirements are satisfied with regards to
blocking strict-match phone numbers. It is recommended that those other features
be labeled as advanced features to avoid confusion with the basic
number-blocking feature.
</p>

<h3 id="apis">APIs</h3>

<p>
Here are the APIs in use:
</p>
<ul>
<li><code><a
href="http://developer.android.com/reference/android/telecom/TelecomManager.html">TelecomManager</a>
API</code>
  <ul>
 <li><code>Intent createManageBlockedNumbersIntent()</code>
  </ul>
</li>
<li><code><a
href="http://developer.android.com/reference/android/telephony/CarrierConfigManager.html">Carrier
Config</a></code>
  <ul>
 <li><code>KEY_DURATION_BLOCKING_DISABLED_AFTER_EMERGENCY_INT</code>
  </ul>
</li>
<li>Please refer to  <code>BlockedNumberContract</code>
  <ul>
 <li>APIs provided by <code><a
 href="https://developer.android.com/reference/android/provider/BlockedNumberContract.html">BlockedNumberContract</a></code></li>
 <li><code>boolean isBlocked(Context context, String phoneNumber)</code></li>
 <li><code>int unblock(Context context, String phoneNumber)</code></li>
 <li><code>boolean canCurrentUserBlockNumbers(Context context)</code></li>
  </ul>
 </li>
</ul>

<h3 id="user-interface">User interface</h3>
<p>
The BlockedNumbersActivity.java user interface provided in AOSP can be used as
is. Device implementers may also implement their own version of the UI, as long as it
satisfies related CDD requirements.
</p>

<p>
Please note, the partners PC application for backup and restore may be needed
to implement restoration of the block list by using
<code>BlockedNumberProvider</code>. See the images below for the blocked
numbers interface supplied in AOSP.
</p>

<img src="images/block-numbers-ui.png" alt="block numbers user interface" width="665" id="block-numbers-ui" />
<p class="img-caption">
  <strong>Figure 2.</strong> Block phone numbers user interface
</p>

<h2 id="validation">Validation</h2>

<p>
Implementers can ensure their version of the feature works as intended by
running the following CTS tests:
</p>

<pre class="devsite-click-to-copy">
android.provider.cts.BlockedNumberContractTest
com.android.cts.numberblocking.hostside.NumberBlockingTest
android.telecom.cts.ExtendedInCallServiceTest#testIncomingCallFromBlockedNumber_IsRejected
android.telephony.cts.SmsManagerTest#testSmsBlocking
</pre>

<p>
The <code>BlockedNumberProvider</code> can be manipulated using <code>adb</code> commands
after running <code>$ adb root</code>. For example:
</p>
<pre class="devsite-click-to-copy">
<code class="devsite-terminal">adb root</code>
<code class="devsite-terminal">adb shell content query --uri content://com.android.blockednumber/blocked</code>
<code class="devsite-terminal">adb shell content insert --uri / content://com.android.blockednumber/blocked --bind / original_number:s:'6501002000'</code>
<code class="devsite-terminal">adb shell content delete --uri / content://com.android.blockednumber/blocked/1</code>
</pre>

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