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<html devsite>
<head>
<title>Implementing TEXTCLASSIFIER</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
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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.
-->
<h2 id="overview">Overview</h2>
<p>
Android 8.1 introduces the TextClassfier API that uses machine learning
techniques to help developers classify text:
</p>
<pre
class="prettyprint">TextClassificationManager tcm =
context.getSystemService(TextClassificationManager.class);
TextClassifier classifier = tcm.getTextClassifier();
TextSelection selection = classifier.suggestSelection(...);
TextClassification classification = classifier.classifyText(...);
</pre>
<p>
Developers may choose to set a custom text classifier:
</p>
<p>
<code>tcm.setTextClassifier(customTextClassifier);</code>
</p>
<p>
But if an app developer sets the text classifier to null, a system default text
classifier is returned for <code>getTextClassifier()</code>.
</p>
<p>
See: <code>android.view.textclassifier.TextClassifierImpl</code>
</p>
<p>
TextView and WebView use the TextClassifier for smart selection and smart text
share features:
</p>
<img src="/devices/tech/display/images/textclassifier.png">
<p class="img-caption">
<b>Figure 1.</b> TEXTCLASSIFIER usage.
</p>
<h2 id="textclassifier-neural-net-models">TextClassifier neural-net models</h2>
<p>
The Android Open Source Project (AOSP) features a number of neural network
models for classifying text. Each model file is trained for a single language.
You may choose to install any combination of models. The models are defined in:
</p>
<p>
<code>external/libtextclassifier/Android.mk</code>
</p>
<h2 id="pre-installing-language-models-on-devices">Pre-installing language
models on devices</h2>
<p>
You may specify a bundle of language models and install them on a device:
</p>
<pre
class="prettyprint"># -----------------------
# Smart Selection bundles
# -----------------------
include $(CLEAR_VARS)
LOCAL_MODULE := textclassifier.smartselection.bundle1
LOCAL_REQUIRED_MODULES := textclassifier.smartselection.en.model
LOCAL_REQUIRED_MODULES += textclassifier.smartselection.es.model
LOCAL_REQUIRED_MODULES += textclassifier.smartselection.de.model
LOCAL_REQUIRED_MODULES += textclassifier.smartselection.fr.model
include $(BUILD_STATIC_LIBRARY)
</pre>
<p>
For example, in <code>device/google/marlin/device-common.mk</code>
</p>
<pre
class="prettyprint"># TextClassifier smart selection model files
PRODUCT_PACKAGES += \
textclassifier.smartselection.bundle1
</pre>
<h2 id="inspecting-installed-language-modules">Inspecting installed language
modules</h2>
<p>
Use ADB to list the files in the directory:
</p>
<pre
class="prettyprint">$ adb shell ls -l /etc/textclassifier
-rw-r--r-- 1 root root ... textclassifier.smartselection.de.model
-rw-r--r-- 1 root root ... textclassifier.smartselection.en.model
-rw-r--r-- 1 root root ... textclassifier.smartselection.es.model
-rw-r--r-- 1 root root ... textclassifier.smartselection.fr.model
</pre>
<h2 id="gservices-model-updates">Model updates</h2>
<p>
Models can be updated either by having a new model included as part of a system image update,
or dynamically via having a system component that would trigger an update through the
System <code>API ACTION_UPDATE_SMART_SELECTION</code> intent. By broadcasting this System API
intent, the framework is able to update the language model of the currently set language.
The models themselves contain the supported
language and a version number so the latest appropriate model is used.
</p>
<p>
So you don't need to preload models for all languages because they can be added later.
If no model file is found for the specified language, text classification will return no-op values.
</p>
<h2 id="compatibility-test-suite-tests">Compatibility Test Suite tests</h2>
<p>
The associated Android Compatibility Test Suite (CTS) tests can be found in:
</p>
<p>
<code>cts/tests/tests/view/src/android/view/textclassifier/cts/TextClassificationManagerTest.java</code>
</p>
<p>
<code>cts/tests/tests/widget/src/android/widget/cts/TextViewTest.java</code>
</p>
<ul>
<li><code>testSmartSelection</code></li>
<li><code>testSmartSelection_dragSelection</code></li>
<li><code>testSmartSelection_resetSelection</code></li>
</ul>
</body>
</html>
|
