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diff --git a/en/devices/architecture/hidl-java/interfaces.html b/en/devices/architecture/hidl-java/interfaces.html deleted file mode 100644 index 024b64ce..00000000 --- a/en/devices/architecture/hidl-java/interfaces.html +++ /dev/null @@ -1,151 +0,0 @@ -<html devsite> - <head> - <title>Interface Methods & Errors</title> - <meta name="project_path" value="/_project.yaml" /> - <meta name="book_path" value="/_book.yaml" /> - </head> - <body> - <!-- - Copyright 2017 The Android Open Source Project - - Licensed under the Apache License, Version 2.0 (the "License"); - you may not use this file except in compliance with the License. - You may obtain a copy of the License at - - http://www.apache.org/licenses/LICENSE-2.0 - - Unless required by applicable law or agreed to in writing, software - distributed under the License is distributed on an "AS IS" BASIS, - WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. - See the License for the specific language governing permissions and - limitations under the License. - --> - -<p>This section details interface methods and errors.</p> - -<h2 id=void>Void methods</h2> -<p>Methods that do not return results are translated into Java methods that -return <code>void</code>. For example, the HIDL declaration:</p> - -<pre class="prettyprint"> -doThisWith(float param); -</pre> - -<p>… becomes:</p> - -<pre class="prettyprint"> -void doThisWith(float param); -</pre> - -<h2 id=single-result>Single-result methods</h2> -<p>Methods that return a single result are translated into their Java -equivalents also returning a single result. For example, the following:</p> - -<pre class="prettyprint"> -doQuiteABit(int32_t a, int64_t b, - float c, double d) generates (double something); -</pre> - -<p>… becomes:</p> - -<pre class="prettyprint"> -double doQuiteABit(int a, long b, float c, double d); -</pre> - - -<h2 id=multiple-result>Multiple-result methods</h2> -<p>For each method that returns more than one result, a callback class is -generated that supplies all the results in its <code>onValues</code> method. -That callback acts as an additional parameter to the method. For example, the -following:</p> - -<pre class="prettyprint"> -oneProducesTwoThings(SomeEnum x) generates (double a, double b); -</pre> - -<p>… becomes:</p> - -<pre class="prettyprint"> -public interface oneProducesTwoThingsCallback { - public void onValues(double a, double b); -} -void oneProducesTwoThings(byte x, oneProducesTwoThingsCallback cb); -</pre> - -<p>A caller of <code>oneProducesTwoThings()</code> would typically use an -anonymous inner class or lambda to implement the callback locally:</p> - -<pre class="prettyprint"> -someInstanceOfFoo.oneProducesTwoThings( - 5 /* x */, - new IFoo.oneProducesTwoThingsCallback() { - @Override - void onValues(double a, double b) { - // do something interesting with a and b. - ... - }}); -</pre> - -<p>or:</p> - -<pre class="prettyprint"> -someInstanceOfFoo.oneProducesTwoThings(5 /* x */, - (a, b) -> a > 3.0 ? f(a, b) : g(a, b))); -</pre> - -<p>You can also define a class to use as a callback … </p> - -<pre class="prettyprint"> -class MyCallback implements oneProducesTwoThingsCallback { - public void onValues(double a, double b) { - // do something interesting with a and b. - } -} -</pre> - -<p>… and pass an instance of <code>MyCallback</code> as the third parameter to -<code>oneProducesTwoThings()</code>.</p> - -<h2 id=errors>Transport errors and death recipients</h2> -<p>Because service implementations can run in a different process, in some cases -the client can stay alive even when the process implementing an interface dies. -Calls on an interface object hosted in a dead process fail with a transport -error (a runtime exception thrown by the called method). Recovery from such a -failure is possible by requesting a new instance of the service by calling -<code>I<InterfaceName>.getService()</code>. However, this method works -only if the process that crashed has restarted and re-registered its services -with the servicemanager (which is generally true for HAL implementations).</p> - -<p>Clients of an interface can also register a <em>death recipient</em> to get a -notification when a service dies. Transport errors can still occur if a call is -made just as the server dies. To register for such notifications on a retrieved -<code>IFoo</code> interface, a client can do the following:</p> - -<pre class="prettyprint"> -foo.linkToDeath(recipient, 1481 /* cookie */); -</pre> - -<p>The <code>recipient</code> parameter must be an implementation of the -interface <code>HwBinder.DeathRecipient</code> provided by HIDL. The interface -contains a single method <code>serviceDied()</code> that is called when the -process hosting the interface dies.</p> - -<pre class="prettyprint"> -final class DeathRecipient implements HwBinder.DeathRecipient { - @Override - public void serviceDied(long cookie) { - // Deal with service going away - } -} -</pre> - -<p>The <code>cookie</code> parameter contains the cookie that was passed with -the call to <code>linkToDeath()</code>. It's also possible to unregister a death -recipient after registering it using:</p> - -<pre class="prettyprint"> -foo.unlinkToDeath(recipient); -</pre> - - </body> -</html> |