docs/html/guide/developing/tools/proguard.jd

page.title=ProGuard
parent.title=Tools
parent.link=index.html
@jd:body

 <div id="qv-wrapper">
    <div id="qv">
      <h2>In this document</h2>

      <ol>
        <li><a href="#enabling">Enabling ProGuard</a></li>

        <li><a href="#configuring">Configuring ProGuard</a></li>

        <li>
          <a href="#decoding">Decoding Obfuscated Stack Traces</a>

          <ol>
            <li><a href="#considerations">Debugging considerations for published
            applications</a></li>
          </ol>
        </li>
      </ol>

      <h2>See also</h2>

      <ol>
        <li><a href="http://proguard.sourceforge.net/manual/introduction.html">ProGuard
        Manual &raquo;</a></li>

        <li><a href="http://proguard.sourceforge.net/manual/retrace/introduction.html">ProGuard
        ReTrace Manual &raquo;</a></li>
      </ol>
    </div>
  </div>

  <p>The ProGuard tool shrinks, optimizes, and obfuscates your code by removing unused code and
  renaming classes, fields, and methods with semantically obscure names. The result is a smaller
  sized <code>.apk</code> file that is more difficult to reverse engineer. Because ProGuard makes your
  application harder to reverse engineer, it is important that you use it
  when your application utilizes features that are sensitive to security like when you are
  <a href="{@docRoot}guide/publishing/licensing.html">Licensing Your Applications</a>.</p>

  <p>ProGuard is integrated into the Android build system, so you do not have to invoke it
  manually. ProGuard runs only when you build your application in release mode, so you do not 
  have to deal with obfuscated code when you build your application in debug mode. 
  Having ProGuard run is completely optional, but highly recommended.</p>
  
  <p>This document describes how to enable and configure ProGuard as well as use the
  <code>retrace</code> tool to decode obfuscated stack traces.</p>

  <h2 id="enabling">Enabling ProGuard</h2>

  <p>When you create an Android project, a <code>proguard.cfg</code> file is automatically
  generated in the root directory of the project. This file defines how ProGuard optimizes and
  obfuscates your code, so it is very important that you understand how to customize it for your
  needs. The default configuration file only covers general cases, so you most likely have to edit
  it for your own needs. See the following section about <a href="#configuring">Configuring ProGuard</a> for information on 
  customizing the ProGuard configuration file.</p>

  <p>To enable ProGuard so that it runs as part of an Ant or Eclipse build, set the
  <code>proguard.config</code> property in the <code>&lt;project_root&gt;/project.properties</code>
  file. The path can be an absolute path or a path relative to the project's root.</p>
<p>If you left the <code>proguard.cfg</code> file in its default location (the project's root directory),
you can specify its location like this:</p>
<pre class="no-pretty-print">
proguard.config=proguard.cfg
</pre>
<p>
You can also move the the file to anywhere you want, and specify the absolute path to it:
</p>
<pre class="no-pretty-print">
proguard.config=/path/to/proguard.cfg
</pre>


  <p>When you build your application in release mode, either by running <code>ant release</code> or
  by using the <em>Export Wizard</em> in Eclipse, the build system automatically checks to see if
  the <code>proguard.config</code> property is set. If it is, ProGuard automatically processes
  the application's bytecode before packaging everything into an <code>.apk</code> file. Building in debug mode
  does not invoke ProGuard, because it makes debugging more cumbersome.</p>

  <p>ProGuard outputs the following files after it runs:</p>

  <dl>
    <dt><code>dump.txt</code></dt>
    <dd>Describes the internal structure of all the class files in the <code>.apk</code> file</dd>

    <dt><code>mapping.txt</code></dt>
    <dd>Lists the mapping between the original and obfuscated class, method, and field names. 
    This file is important when you receive a bug report from a release build, because it 
    translates the obfuscated stack trace back to the original class, method, and member names.
    See <a href="#decoding">Decoding Obfuscated Stack Traces</a> for more information.</dd>

    <dt><code>seeds.txt</code></dt>
    <dd>Lists the classes and members that are not obfuscated</dd>

    <dt><code>usage.txt</code></dt>
    <dd>Lists the code that was stripped from the <code>.apk</code></dd>
  </ul>

  <p>These files are located in the following directories:</p>

  <ul>
    <li><code>&lt;project_root&gt;/bin/proguard</code> if you are using Ant.</li>

    <li><code>&lt;project_root&gt;/proguard</code> if you are using Eclipse.</li>
  </ul>

  
  <p class="caution"><strong>Caution:</strong> Every time you run a build in release mode, these files are
  overwritten with the latest files generated by ProGuard. Save a copy of them each time you release your
  application in order to de-obfuscate bug reports from your release builds. 
  For more information on why saving these files is important, see 
  <a href="#considerations">Debugging considerations for published applications</a>.
  </p>

  <h2 id="configuring">Configuring ProGuard</h2>

  <p>For some situations, the default configurations in the <code>proguard.cfg</code> file will
  suffice. However, many situations are hard for ProGuard to analyze correctly and it might remove code
  that it thinks is not used, but your application actually needs. Some examples include:</p>

  <ul>
    <li>a class that is referenced only in the <code>AndroidManifest.xml</code> file</li>

    <li>a method called from JNI</li>

    <li>dynamically referenced fields and methods</li>
  </ul>

  <p>The default <code>proguard.cfg</code> file tries to cover general cases, but you might
  encounter exceptions such as <code>ClassNotFoundException</code>, which happens when ProGuard
  strips away an entire class that your application calls.</p>

  <p>You can fix errors when ProGuard strips away your code by adding a <code>-keep</code> line in
  the <code>proguard.cfg</code> file. For example:</p>
  <pre>
-keep public class &lt;MyClass&gt;
</pre>

  <p>There are many options and considerations when using the <code>-keep</code> option, so it is
  highly recommended that you read the <a href="http://proguard.sourceforge.net/manual/introduction.html">ProGuard
  Manual</a> for more information about customizing your configuration file. The <a href=
  "http://proguard.sourceforge.net/manual/usage.html#keepoverview">Overview of Keep options</a> and
  <a href="http://proguard.sourceforge.net/index.html#/manual/examples.html">Examples section</a>
  are particularly helpful. The <a href=
  "http://proguard.sourceforge.net/manual/troubleshooting.html">Troubleshooting</a> section of the
  ProGuard Manual outlines other common problems you might encounter when your code gets stripped
  away.</p>

  <h2 id="decoding">Decoding Obfuscated Stack Traces</h2>

  <p>When your obfuscated code outputs a stack trace, the method names are obfuscated, which makes
  debugging hard, if not impossible. Fortunately, whenever ProGuard runs, it outputs a
  <code>&lt;project_root&gt;/bin/proguard/mapping.txt</code> file, which shows you the original
  class, method, and field names mapped to their obfuscated names.</p>

  <p>The <code>retrace.bat</code> script on Windows or the <code>retrace.sh</code> script on Linux
  or Mac OS X can convert an obfuscated stack trace to a readable one. It is located in the
  <code>&lt;sdk_root&gt;/tools/proguard/</code> directory. The syntax for executing the 
  <code>retrace</code> tool is:</p>
  <pre>retrace.bat|retrace.sh [-verbose] mapping.txt [&lt;stacktrace_file&gt;]</pre>
  <p>For example:</p>
  
  <pre>retrace.bat -verbose mapping.txt obfuscated_trace.txt</pre>
  
  <p>If you do not specify a value for <em>&lt;stacktrace_file&gt;</em>, the <code>retrace</code> tool reads
  from standard input.</p>

  <h3 id="considerations">Debugging considerations for published applications</h3>

  <p>Save the <code>mapping.txt</code> file for every release that you publish to your users. 
  By retaining a copy of the <code>mapping.txt</code> file for each release build, 
  you ensure that you can debug a problem if a user encounters a bug and submits an obfuscated stack trace.
  A project's <code>mapping.txt</code> file is overwritten every time you do a release build, so you must be
  careful about saving the versions that you need.</p>

  <p>For example, say you publish an application and continue developing new features of
  the application for a new version. You then do a release build using ProGuard soon after. The
  build overwrites the previous <code>mapping.txt</code> file. A user submits a bug report
  containing a stack trace from the application that is currently published. You no longer have a way 
  of debugging the user's stack trace, because the <code>mapping.txt</code> file associated with the version
  on the user's device is gone. There are other situations where your <code>mapping.txt</code> file can be overwritten, so
  ensure that you save a copy for every release that you anticipate you have to debug.</p>

  <p>How you save the <code>mapping.txt</code> file is your decision. For example, you can rename them to
  include a version or build number, or you can version control them along with your source
  code.</p>